Advances in High-Temperature Sensor Technologies: Material System, Sensing Principles, Drift Compensation, and Encapsulation Reliability

Abstract

High-temperature sensors are irreplaceable for extreme-environment monitoring in aerospace, automotive, marine, and industry applications. This review synthesizes critical advances in materials, sensing principles, drift compensation, signal transmission, and encapsulation reliability. We analyze high-temperature-resistant ceramics, metals, crystalline materials, wide-band gap semiconductors, and high-entropy alloys, highlighting their operational mechanisms under high-temperature conditions. Subsequently, seven typical high-temperature sensing principles including fiber Bragg grating, LC resonance, Hall effect, magnetostriction, piezoelectric effect, Seebeck effect, and thermoelectric effect are expounded. Furthermore, the roles of software compensation strategies (curve fitting and neural networks) and hardware compensation approaches (material optimization and circuit design) in suppressing temperature drift are discussed. In addition, the thermomechanical reliability design of packaging technologies such as high-temperature tubular encapsulation, solid-state isolation encapsulation, substrate encapsulation, and leadless encapsulation is comprehensively reviewed. Finally, the operational performance of high-temperature sensors in high-temperature scenarios, such as automotive powertrains, aircraft engines, and marine turbines, is detailed. This review provides theoretical guidance and technical references for material selection, sensing principle innovation, and engineering implementation of high-temperature sensors.

Introduction

With the increasing demand for precision measurements, significant advancements have been achieved in sensing technology. Progress in micromachining and microelectromechanical systems (MEMS) processes has driven sensor development toward miniaturization, enhanced precision, and improved sensitivity. These sensors are now extensively deployed across automotive, industrial manufacturing, and aerospace sectors, where they monitor and regulate system operations through multisource data acquisition. However, accurate and reliable system monitoring remains a critical challenge in extreme environments characterized by ultrahigh temperatures, humidity, pressure, or strong magnetic fields.

High-temperature environments prevail in operational systems such as aerospace platforms, industrial manufacturing equipment, and high-efficiency engines. Conventional high-precision sensors typically exhibit significant performance degradation upon direct exposure to such high-temperature conditions. This degradation primarily stems from structure failure, material creep, and thermal degradation of the conductive layers under elevated temperatures. Consequently, sensors operating in high-temperature applications must incorporate specialized design elements: high-temperature-resistant materials, dedicated sensing principles, effective temperature compensation mechanisms, and robust encapsulation technologies to mitigate performance degradation in thermal environments.

The mid-20th century industrial revolution spurred urgent demands for high-temperature monitoring in the metallurgical and chemical industries. During this period, thermocouples emerged as the predominant solution for industrial temperature monitoring. However, their measurement accuracy in extreme thermal environments proved to be insufficient due to inherent material limitations of metallic components (typically below 800 °C). Ceramic materials subsequently gained prominence in high-temperature sensing applications owing to their superior structural stability, mechanical strength, and thermal resistance compared to metals. , These ceramics serve dual functions as both sensing elements/substrates and encapsulation materials. The 1960–1980 period witnessed transformative advances with the advent of fiber optic technology. Fiber optic sensors became widely adopted in aerospace applications due to their exceptional electromagnetic interference immunity and thermal stability. − Subsequent introduction of sapphire fibers further enhanced operational temperature limits. Concurrently, although semiconductor technology progressed rapidly, conventional semiconductor materials remained unsuitable for high-temperature sensing applications, while wide-bandgap semiconductors found primary application in nuclear field. Microelectromechanical systems (MEMS) technology catalyzed sensor miniaturization during 1980–1990. To enable operation in high-temperature environments, emerging high-temperature resistant materials (SiC, SiCN) were utilized for fabricating microscale sensors. This technological evolution concurrently facilitated the development of inductive-capacitive (LC) resonant and piezoelectric sensors. A pivotal innovation occurred in 1988 with the adaptation of low-temperature cofired ceramic (LTCC) technology for manufacturing of LC resonant passive high-temperature pressure sensors, − later enhanced through the HTCC implementation. In 1997, MEMS-based SiC piezoresistive sensors effectively addressed the thermal limitations of silicon-based materials at elevated temperatures. Subsequent breakthroughs emerged in 2007 with the development of alloy composition optimization (e.g., rare-earth-doped iron–cobalt materials), achieving unprecedented properties including a Curie temperature of 366.3 °C and saturation magnetostriction coefficient of 28 × 10^–6, which substantially advanced high-temperature magnetostrictive sensor capabilities. The discovery of wide-bandgap semiconductors (SiC, GaN) in 2010 provided superior electronic properties, enabling transformative progress in GaN-based high-temperature Hall sensors. By 2014, rare-earth calcium oxyborate single crystals ReCa₄O­(BO₃)₃ (ReCOB, where Re = Gd, La, Y) demonstrated exceptional characteristics for ultrahigh temperature applications, featuring extremely high resistivity, stable piezoelectric coefficients, and operational stability up to 1250 °C. Parallel advances in fabrication techniques occurred between 2017 and 2018, where femtosecond laser point-by-point and line-by-line writing techniques enabled high-performance sapphire fiber grating manufacturing. , Most recently, emerging high-entropy ceramic materials exhibiting extraordinary thermal stability have signaled promising pathways for next-generation high-temperature sensor development.

This review comprehensively examines recent advancements in high-temperature sensing technologies, focusing on five critical domains: novel refractory materials, fundamental sensing principles, signal transmission, temperature compensation methodologies, and advanced encapsulation architectures. The analysis encompasses specific applications across automotive, aerospace, marine, and industry fields. We systematically evaluate emerging materialsincluding GaN, SiC, high-entropy materials, and ReCOB for high-temperature sensing, providing comparative assessment of their respective advantages and limitations. The work further contrasts diverse signal transmission strategies for extreme thermal environments. The key challenges are elaborated in depth, including multiphysics failure mechanisms under thermomechanical–electrochemical coupling, thermal expansion coefficient mismatches between high-temperature resistant components, high-temperature degradation effects on fundamental sensing principles, electromagnetic interference susceptibility in wireless transmission, compensation system latency and associated measurement errors, interfacial material thermal diffusion, long-term encapsulation degradation, etc. Finally, we present a forward-looking perspective on the developmental trajectories for next-generation high-temperature sensing systems.

Key Materials for High-Temperature Sensors

High-temperature resistant materials constitute the cornerstone of high-temperature sensor performance, fundamentally dictating critical parameters including maximum operating temperature, long-term stability, and measurement accuracy. The ultimate thermal tolerance of these material directly constrains the sensor’s operational ceiling, while their physical and chemical properties, particularly chemical stability and thermal expansion coefficient, profoundly affect measurement reliability under high-temperature environments. Ceramics and metals represent conventional workhorses in this domain, and emerging material systems such as composites, high-entropy materials, and wide-bandgap semiconductors demonstrate compelling advantages for next-generation applications.

Ceramic Materials

Ceramic materials serve as ideal substrates and functional elements for high-temperature sensors owing to their excellent high-temperature stability (melting points typically exceeding 2000 °C), chemical inertness (resisting reactions at elevated temperatures), and low thermal conductivity (providing intrinsic thermal insulation). Certain ceramics further exhibit specialized electrical properties, including high dielectric constants and piezoelectric effects, enabling their direct utilization as sensing elements.

Silicon Nitride (Si₃N₄) Ceramics

Si₃N₄ ceramics characterized by strong covalent bonding demonstrate outstanding mechanical and thermal properties: high hardness, superior fracture strength, low thermal expansion coefficient, low high-temperature creep, oxidation resistance, and stable dielectric behavior (ε_r = 9.4∼9.5) under high-temperature conditions. − Their atomic structure features [SiN₄] tetrahedra with center silicon atom coordinated to four nitrogen vertices, forming a continuous three-dimensional network. , This configuration confers exceptional stability in extreme environments involving high temperatures, high pressures, and chemical corrosion. However, these advantageous properties simultaneously contribute to significant machining challenges and increased manufacturing costs.

Zeng et al. implemented Si₃N₄ encapsulation of graphene pressure sensors, creating oxygen-isolating rectangular cavities that extended operational temperature limits (Figure a). Su et al. developed a wireless passive high-temperature sensor using Si₃N₄ discs as sensing media. As illustrated in Figure b, Pt electrodes deposited on opposing surfaces and etched a complementary split ring resonator (CSRR), leveraging the positive temperature coefficient of Si₃N₄’s dielectric constant. Resonant frequency shifts follow established equivalent circuit models (eqs and ), where fixed structural parameters determine equivalent inductance (L _S1, L _S2) and capacitance (C _S1, C _S2). The temperature-induced dielectric constant of the Si₃N₄ elevation reduces interelectrode coupling capacitance (C _r) between the upper and lower electrodes, thereby modulating resonant frequency.

$$f_0=\frac{1}{2\pi \sqrt{\frac{L_{\mathrm{S1}}+L_{\mathrm{S2}}}{L_{\mathrm{S1}}{L}_{\mathrm{S2}}}(C_{\mathrm{S1}}+C_{\mathrm{S2}}+C_{\mathrm{r}})}}$$ 1

$$C_{\mathrm{r}}=\frac{{\epsilon }_{\mathrm{s}}}{4\pi kd}$$ 2

where ε denotes the dielectric constant of Si₃N₄; S represents the effective overlapping electrode area; d is the interelectrode spacing; and k corresponds to the configuration-dependent electrostatic constant.

1.

High-temperature resistant materials in sensor applications. (a) Manufacturing process of graphene pressure sensor fabrication with Si₃N₄ encapsulation featuring rectangular cavities; (b) Multilayer architecture of wireless passive high-temperature sensor; (c) Surface morphology of annealed ITO thin films postdeposition; (d) Alumina-based pressure sensor fabrication process; (e) SiC capacitive pressure sensor manufacturing workflow; (f) Wireless SiCN sensor structure for high-temperature and high-voltage environments; (g) Operational principle of zirconia oxygen sensors; (h) TFTC sensor structure design; (i) Focused ion beam (FIB) micrographs of 30 nm W/200 nm TaN/400 nm Pt multilayers after 1000 °C/24 h annealing.

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Alumina (Al₂O₃) Ceramics

Al₂O₃ ceramics characterized by high melting points (∼2072 °C), low thermal expansion coefficients (ensuring dimensional stability under thermal cycling), and excellent chemical resistance, serve as prevalent substrates and encapsulation materials for high-temperature sensors. Their thermal stability originates from the α-Al₂O₃ crystal structure, a hexagonally close-packed lattice where oxygen ions form the framework with aluminum ions occupying octahedral interstices, which exhibits exceptionally high lattice energy. , However, its limited electrical conductivity often necessitates compounding with other functional materials for sensing applications.

Zhang et al. demonstrated that sputter-deposited Al₂O₃ coatings significantly enhance the high-temperature stability of indium tin oxide (ITO) films by suppressing, recrystallization, and oxygen diffusion. Postdeposition annealing at 800 °C for 3 h proved critical for stress relief, though excessive Al₂O₃ doping (≥7%) induced grain coarsening and microcracking due to thermal mismatch (Figure c). Optimal performance was achieved at a 4% Al₂O₃ concentration. Concurrently, Tan et al. developed a laminated Al₂O₃ capacitive pressure sensor featuring sacrificial carbon-filled cavities (Figure d). During sintering, carbon oxidation generates sealed cavities whose pressure-induced deformation alters electrode spacing, thereby modulating capacitance and resonant frequency. While operational at 850 °C, this design exhibited 8.3% repeatability error, 5.05% hysteresis error, and 1% zero drift and was limited to ∼20 min duration. Earlier innovations include Allen et al.’s 450 °C LTCC-based LC resonator , and Hong’s HTCC capacitor sustaining 1500–1800 °C, with Xiong later implementing zirconia-alumina HTCC cavities for pressure sensing.

Silicon Carbide (SiC) Ceramics

SiC occupy a pivotal role in modern high-temperature sensors due to their excellent high-temperature resistance (1600 °C), excellent high-temperature mechanical strength, outstanding creep resistance, low thermal expansion coefficient, high thermal conductivity, and good thermal shock tolerance. , These properties stem from its strong Si–C covalent bonding and stable crystal structure. However, SiC ceramics exhibit susceptibility to high-temperature oxidation and face inherent challenges in their machinability and production costs. Chen et al. fabricated LPCVD-derived suspended SiC diaphragms for capacitive sensors, achieving operation at 295–305 °C and 700 psi through optimized membrane-substrate compatibility (Figure e). Nevertheless, temperature-dependent sensitivity reduction and linearity degradation were observed.

High-Temperature Piezoelectric Ceramics

Barium titanium silicate ceramics (Ba₂TiSi₂O₈; BTS) demonstrates high Curie temperature (∼675 °C) and exhibits excellent piezoelectric coefficients (d ₁₅ = 17.8 pC/N, d ₃₁ = 2.9 pC/N, d ₃₃ = 4.0 pC/N) − and good thermal stability (CTE ≈ 9.4 × 10^–6/°C) under high-temperature conditions. Jiang et al. systematically investigated the thermal expansion behavior and dielectric thermoses properties of BTS ceramics. Strontium-substituted variants (Ba_{2 – x} Sr _x TiSi₂O₈) enhance the performance. The results demonstrate that increased Sr content elevates both piezoelectric constants and phase transition temperatures, thereby enabling piezoelectric vibration sensors to operate at 600 °C.

Other Functional Ceramic Materials

Silicon carbonitride (SiCN) ceramics combine semiconductor properties with mechanical robustness (high hardness, wear resistance) and thermal stability, serving dual sensing functions. , Rongding and Qiannan developed a wireless high-temperature pressure sensor using SiCN as the dielectric layer (Figure f), where pressure-induced dielectric variations shift resonant frequency. SiCN also enables temperature sensing through predictable dielectric constant-temperature relationships governed by eqs –.

$$\mathrm{{\rm E}}={\epsilon }_{\alpha }+\frac{{\epsilon }_{\mathrm{s}}-{\epsilon }_{\alpha }}{1+{\omega }^2+\tau (T{)}^2}$$ 3

where ε_s denotes the static permittivity, ε_α represents the high-frequency relative permittivity, ω is the angular frequency, and τ­(T) indicates the temperature-dependent relaxation time.

$$\tau (T)={\tau }_0\exp \left(\frac{E_{\alpha }}{RT}\right)$$ 4

where T represents the absolute temperature, τ₀ is the pre-exponential factor, E _α denotes the activation energy, and R indicates the universal gas constant.

$$\begin{array}{c}K=\frac{\mathrm{d}\epsilon /\epsilon }{\mathrm{d}p}=\frac{\partial ln\epsilon }{\partial p}\end{array}$$ 5

where ε is the relative permittivity and p denotes pressure, exhibiting positive pressure dependence.

$$\begin{array}{c}\frac{\partial ln\alpha }{\partial p}=\frac{3}{\epsilon }\frac{\partial ln\epsilon }{\partial p}\end{array}$$ 6

where α represents the atomic polarizability. SiCN’s intrinsic properties enhance dipolar polarization under compressive stress.

Zirconia ceramics (ZrO₂) maintain exceptional chemical stability and operational reliability at temperatures up to 1000 °C , while exhibiting significant oxygen ion conductivity within the 650–1200 °C range. Oxygen partial pressure differentials across ZrO₂ membranes induce directional ion migration, generating concentration gradient electromotive force. , This effect can be used to fabricate high-temperature oxygen sensors (Figure g). Alshammari et al. successfully incorporated ZrO₂ into PVA via structural design and composition optimization, achieving a synergistic enhancement of thermal, optical, and mechanical properties. The resulting material, characterized by its uniformly dispersed nanostructure, improved thermal stability, and tunable optical behavior, opens new avenues for advanced functional materials with particularly promising applications in flexible electronics, energy conversion, and thermal management.

Metallic Materials

Metallic materials enable high-temperature sensing through their intrinsic properties, such as inductance, capacitance, magnetism, etc. Tungsten (W) and platinum (Pt) are the representative materials. Suitable metals must possess high melting points, excellent thermal stability, elevated electrical conductivity, low thermal expansion coefficients, and suitable resistivity to ensure signal integrity under thermal stress.

W maintains exceptional strength and hardness at extreme temperatures (melting point 3422 °C) yet suffers oxidation susceptibility in oxidative environments. W can be combined with rhenium (Re) to form tungsten–rhenium thermocouples, which exploit the Seebeck effect for measurements up to 2300 °C. For instance, Zhang’s MEMS-fabricated thin-film variant (Figure h) employed W-3% Re/W-25% Re electrode pairs where thermal gradients generate measurable potentials. A temperature gradient between the hot and cold junctions induces differential charge carrier diffusion within the conductor, generating a measurable thermoelectric potential through the Seebeck effect.

Pt (melting point of ∼1772 °C) demonstrates outstanding chemical inertness at high temperatures and is not easily oxidized and corroded. In particular, its monotonic resistivity–temperature relationship enabled precise resistance thermometry between 100 and 500 °C. Han et al. fabricated a Pt thin-film temperature sensor on an alumina substrate using a microelectromechanical systems (MEMS) process. It was found that the Pt thin-film sensor exhibited high precision after annealing at 900 °C.

Composite Metal Materials

The implementation of single-layer metallic conductors in high-temperature sensors presents significant challenges due to intensified interfacial element diffusion between substrate and metal layers at high temperatures. This phenomenon precipitates conductive performance degradation characterized by diminished uniformity and reduced conductivity. Consequently, multilayer composite metallization systems become essential for enhancing thermal stability. Shaobo and Hongtao demonstrated W/TaN/Pt interconnects sustaining electrical stability at 500 °C, where postannealing (1000 °C/24 h) preserved structural integrity of the 30 nm/200 nm/400 nm stack without Pt cracking (Figure i). The Pt layer effectively inhibits the interlayer diffusion of elements; it should be noted that 1000 °C annealing remains essential for Schottky barrier reduction and ohmic contact formation.

Crystalline Materials

Refractory crystalline materials are defined by their capacity to retain intrinsic physical and chemical properties under high-temperature conditions. These materials characterized by high melting points, excellent thermal stability, and robust mechanical behavior, enabled reliable functionality across diverse operational high-temperature environments.

Sapphire achieves operational temperatures exceeding 1900 °C with superior chemical inertness, emerging as a critical platform for fiber-optic sensors through advances in micromachining. Wang et al. pioneered the fabrication of sapphire fiber grating via femtosecond laser point-by-point inscription, achieving devices with 125 μm diameter, 0.6% reflectivity, and 6 nm bandwidth. Subsequent innovation by Xu et al. proposed line-by-line femtosecond laser engraving, which produced 60 μm diameter gratings exhibiting enhanced reflectivity (6.3%) and 6.08 nm bandwidth. Through multilayer line-by-line scanning, Xu et al. further expanded the refractive index modulation area in 60 μm diameter gratings, significantly boosting increased to 34.1% while narrowing bandwidth to 1.74 nm. Most recently, Xu et al. leveraged femtosecond laser filamentation effects for efficient grating production, yielding 100 μm diameter devices with 2.3% reflectivity and 8.84 nm bandwidth.

Piezoelectric Single Crystal Materials

Piezoelectric single crystals are defined by their intrinsic piezoelectric response and characteristically high mechanical quality factors. These materials exhibit superior charge generation per unit stress compared to polycrystalline ceramics, which can be attributed to enhanced electromechanical coupling coefficients. Furthermore, their crystallographic orientation dependence enables exceptional piezoelectric performance along designated crystallographic axes. Typical high-temperature piezoelectric single crystals encompass several prominent systems: lithium niobate (LiNbO₃, LN), gallium phosphate (GaPO₄), lanthanum gallium silicate (La₃Ga₅SiO₁₄, LGS), and rare-earth calcium oxyborates (ReCa₄O­(BO₃)₃, ReCOB, where Re = Gd, La, and Y).

LiNbO₃ adopts a trigonal structure with exceptional properties including a 1150 °C Curie temperature and strong piezoelectric response (d ₃₃ = 19.22 × 10^–11 C/N). , However, chemical decomposition above ∼300 °C and low electrical resistivity limit its high-temperature operational lifetime. Sarker et al. designed ceramic-encapsulated LN sensors, achieving 2–11% measurement deviation versus k-type thermocouples in 200–300 °C boiler environments.

GaPO₄ maintains structural similarity to α-quartz, with α-phase stability persisting to 933 °C. This enables excellent piezoelectric performance up to 970 °C, supported by high resistivity for stable voltage output. Nevertheless, as the temperature increases, the degree of structural disorder increases, and the mechanical quality factor decreases, limiting its application at higher temperatures. Elam et al. demonstrated minimal thermal sensitivity (∼3 Hz/°C) in GaPO₄-based helium pulse frequency measurements within 390∼450 °C environments, outperforming SiO₂ counterparts.

LGS crystals retain physical and chemical stability to 1470 °C with a high dielectric constant (ε₁₁ = 18.27, ε₃₃ = 55.26). However, the migration and diffusion of oxygen vacancies at high temperatures resulted in significant resistivity reduction. Despite this, Nagmani and Behera confirmed stable piezoelectric and electromechanical coupling coefficients across 20∼1000 °C.

ReCOB monoclinic crystals exhibit nonlinear piezoelectric properties from asymmetric lattice centers. Zhang et al. documented ultrahigh resistivity (10⁸ Ω·cm at 800 °C) and temperature-stable dielectric, electromechanical, and piezoelectric properties, establishing ReCOB as a premier candidate for ultrahigh-temperature sensing applications.

Semiconductor Materials

Wide-bandgap semiconductors have emerged as pivotal materials for high-temperature sensing applications, leveraging their substantial band gap energies, exceptional thermal stability, and chemical inertness. Among these, silicon carbide (SiC) and gallium nitride (GaN) represent prominent candidates.

SiC semiconductors primarily employed in single-crystalline forms (such as 4H-SiC, 6H-SiC) − derive their thermal resilience from a wide bandgap (>above 3.0 eV) and low intrinsic carrier concentration. , This bandgap advantage imposes higher energy barriers for valence-to-conduction band transitions, effectively suppressing thermally excited carrier generation at high temperatures. Such characteristics enable stable device operation, as demonstrated by Eickhoff et al. in 500 °C-capable SiC-based MEMS sensors for engine monitoring. Further exploiting this property, Ciuk et al. fabricated graphene-epitaxial Hall sensors on 4H-SiC substrates, where the wide bandgap intrinsically minimizes thermal carrier interference.

As a third-generation semiconductor, GaN sustains operation beyond 600 °C through its 3.4 eV bandgap, 3.3 MV/cm breakdown electric field, 2.5 × 10⁷ cm/s electron saturation velocity, and excellent thermal conductivity. Eickhoff et al. documented advances in AlGaN/GaN heterostructure sensors, notably Pt/GaN Schottky diodes detecting hydrogen and hydrogen-containing species at 600 °C and GaN-based FETs operating at 400 °C, alongside pH-sensitive surface characteristics.

High-Entropy Materials (HEMs)

HEMs comprise five or more principal elements in nearly equal molar ratios, − exhibiting four defining characteristics: configurational entropy maximization, severe lattice distortion, sluggish diffusion kinetics, and synergistic cocktail effects. , The high-entropy effect stabilizes single-phase structures through Gibbs free energy minimization, − while atomic size mismatch induces lattice distortion that enhance strength, hardness, and radiation tolerance. , Elemental interactions impede atomic migration, conferring exceptional thermal stability via sluggish diffusion, , and cocktail effects generate emergent properties (e.g., enhanced catalysis and corrosion resistance) surpassing conventional materials. , Collectively, these mechanisms endow HEMs with unparalleled high-temperature stability.

However, pronounced lattice disorder significantly compromises carrier mobility through intensified electron scattering and constrains electrical transport performance for sensing applications. Addressing this challenge, Sun et al. engineered rare-earth niobate (RENbO₄) thermistors via entropy-stabilized A-site isovalent substitution. This strategy generates high oxygen vacancy concentrations that optimize the electronic structure and structural integrity. Subsequent ″entropy engineering″ through oxygen vacancy manipulation produces stable microstructural features, including twin domains, lattice distortion, and reconstruction, enabling exceptional thermal stability (1% aging drift over 1000 h) and precise temperature response (TCR = 0.223%/K at 1423 K) across 223–1423 K.

Structural and Functional Material Challenges in High-Temperature Sensing

Figure summarizes the high-temperature resistance performance of the aforementioned high-temperature-resistant materials when used as structural and functional materials, respectively. Despite exhibiting exceptional thermal resistance, materials for high-temperature sensors remain vulnerable to failure under thermal–mechanical–electrochemical multifield coupling during service.

2.

Comparative performance metrics of representative high-temperature substrate and functional materials.

Ceramics suffer from inherently low thermal conductivity, inducing thermal stress concentrations during thermal transients that precipitate thermal shock fracture or damage. Concurrently, sustained thermo-mechanical loading promotes creep deformation through defect accumulation, eventually inducing crack propagation or even fracture. When integrated with metallic components, differential thermal expansion coefficients induce elastic element distortion, causing significant temperature drift. Metals experience atomic vibration-amplified modulus reduction in a high-temperature environment: compromising elastic element stiffness and degrading sensor sensitivity and dynamic response. Surface oxidation forms deleterious oxide layers, while prolonged thermal exposure accelerates creep deterioration. Composites face interfacial challenges: metal–matrix composites develop brittle intermetallic compounds through elemental interdiffusion, degrading both conductivity and mechanical strength. Their electrical conduction exhibits nonlinear temperature dependence, with creep emerging under continuous thermo-mechanical stress. Crystalline materials undergo grain boundary slippage as the dominant deformation mechanism, substantially reducing the strength. Enhanced atomic mobility impedes dislocation motion, diminishing strength and toughness while elevated vacancy concentrations accelerate diffusion processes that destabilize the microstructure. Phase transformation and grain boundary precipitates further weaken bond strength, inducing material embrittlement. Semiconductor present fundamental incompatibilities: their intrinsic characteristics (e.g., carrier concentration, band gap, carrier mobility) conflict with extreme environmental conditions through, thermal excitation enhancement, intrinsic carrier excitation, and dopant deactivation.

Fundamental Sensing Principles for High-temperature Sensors

High-temperature sensors employ diverse operational principles, with certain mechanisms, fiber optic sensors, and LC resonance, exhibiting inherent temperature drift resistance due to signal propagation solely dependent on thermal variations. Other principles, while more susceptible to temperature effects, maintain reliable performance in high-temperature environments through adopting high-temperature resistant materials, implementing temperature compensation strategies, or optimizing structural designs.

Fiber Bragg Gratings (FBGs)

Fiber optic sensors can be classified into three categories based on their operating principles: fiber Bragg grating sensors, fluorescent fiber optic sensors, and interferometric fiber optic sensors.

The FBG sensing paradigm exploits Bragg reflection phenomena within optical fibers (Figure a). Since optical signals are inherently insensitive to high temperatures, the use of light propagation in optical fibers as information carriers has become an effective means of high-temperature measurement. , Broadband illumination incidents on periodic refractive index modulations (grating structures) reflects a characteristic Bragg wavelength (λ_B) while transmitting other spectral components. − This wavelength λ_B can be calculated by using eq .

$$\lambda =2n_{\mathrm{eff}}\wedge$$ 7

where n _eff and ∧ denote the effective refractive index and the grating period. External stimuli (pressure and temperature) modulate n _eff and ∧, enabling high-temperature pressure/temperature/bimodal sensors via thermally stable fibers (such as sapphire or rare-earth-doped quartz optical fibers, etc.).

3.

Schematics of representative high-temperature sensing mechanisms. (a) Fiber Bragg grating (FBG) operating principle; (b) Dual-FBG configuration combining single-mode and thin-core fibers for pressure and temperature detection; (c) Sensing principle of fluorescent fiber optic temperature sensor; (d) Dual-mode sensor integrating Fabry–Perot (F–P) resonant cavity with reference resonator; (e) Wireless passive LC resonant sensor design; (f) Wired LC sensing architecture; (g) Hall effect sensor operational mechanism; (h) magnetostrictive sensing element configuration; (i) piezoelectric effect bidirectional transduction. (j) Seebeck effect principle diagram.

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Su et al. implemented FBGs on spliced single-mode fibers (SMF) and thin-core fibers (TCF) (Figure b). Differential core refractive indices and thermo-mechanical responses enable strain–temperature discrimination. Calibrated coefficient-thermal sensitivity (K _TSMF, K _TTCF) and strain sensitivity (Kε_SMF, Kε_TCF) permit solving temperature (△T) and strain (△ε) from resonant wavelength shifts (△λ_SMF, △λ_TCF). The temperature △T and strain △ε can be calculated by using eq .

$$\left[\begin{array}{c}△T\\ △\epsilon \end{array}\right]=\left[\begin{array}{cc}{K}_{T_{\mathrm{SMF}}}& K_{{\epsilon }_{\mathrm{SMF}}}\\ K_{T_{\mathrm{TCF}}}& K_{{\epsilon }_{\mathrm{TCF}}}\end{array}\right]\left[\begin{array}{c}△{\lambda }_{\mathrm{SMF}}\\ △{\lambda }_{\mathrm{TCF}}\end{array}\right]$$ 8

This configuration achieved 3.25 pm/με strain sensitivity at 800 °C (0–1000 με range). A fundamental constraint of this differential measurement approach is its inherent limitation to relative changes; determination of absolute stress and temperature values necessitates prior knowledge of the initial environmental state.

A fluorescent fiber-optic temperature sensor operates by utilizing the changes in fluorescence intensity or wavelength of fluorescent materials under temperature variations. Signals are transmitted through optical fibers to achieve a temperature detection. Fluorescent materials are substances that can absorb light of a certain wavelength and emit light of a longer wavelength. When fluorescent materials are affected by temperature changes, their fluorescence characteristics undergo alterations. Consequently, the temperature value can be determined based on these fluorescence changes. Compared with other high-temperature sensors, it is immune to electromagnetic interference. Moreover, its small size enabled the sensor to perform local temperature measurements. As shown in Figure c, the sensing element is excited by an optical pulse. After this excitation, the fluorescence signal decays in an exponential pattern. The time constant of this exponential trend depends on the temperature, so it can be regarded as an indirect measurement of the temperature.

The fundamental principle of an interferometric fiber-optic sensor is based on the effect of the measured object on the sensitive element (usually a single-mode optical fiber), which causes changes in the refractive index or propagation constant of the sensitive element, thereby leading to a phase change in the light. This phase change results in alterations in the interference fringes produced by two monochromatic light beams. By detecting the amount of change in the interference fringes, the amount of phase change in the light can be determined and, subsequently, information about the measured object can be obtained. Its outstanding advantage lies in its ability to detect minute phase changes, enabling high-precision measurements of small physical variations. Yan et al. proposed a dual Fabry–Perot (F–P) interferometer integrated with FBG in a hollow silicon microsphere cavity (Figure d), leveraging an optical vernier effect for simultaneous pressure–temperature measurement. The reference F–P cavity responds exclusively to temperature, while the sensing F–P cavity reacts to both the temperature and pressure. By referring to the temperature value independently measured by the F–P cavity, the influence of temperature on the sensing F–P cavity can be compensated for, and the accurate decoupling of pressure and temperature can be realized.

LC Resonant Sensing Principle

LC resonant operates through two distinct modalities: wireless passive sensing and active wired sensing, with the former being particularly suited for harsh high-temperature environments. The wireless passive variant comprises two fundamental components. (1) Resonance physics: an inductor (L, typically fixed) and capacitor (C, sensitive to measurands) form a resonant circuit governed by the natural frequency. The resonance frequency f can be calculated using eq .

$$f=\frac{1}{2\pi \sqrt{\mathrm{LC}}}$$ 9

Variations in external stimuli (e.g., pressure, temperature) modulate capacitance, consequently shifting resonant frequency. (2) Wireless interrogation: an external reader coil emits alternating electromagnetic fields that inductively couple with the sensor, simultaneously transferring energy to excite resonance and capturing the frequency-modulated response signal, thus enabling contactless measurement.

Kou et al. designed a dual-LC wireless passive sensor capable of simultaneous force (0–10 N) and temperature (25–500 °C) measurement. This integrated design features two LC circuits, one for the temperature response and the other for the force response, both coupled to a single antenna. Temperature elevation increases the dielectric constant of the Al₂O₃ layer in the temperature circuit, elevating capacitance and reducing resonant frequency (f). Similarly, applied force decreases LC capacitor plate separation in the mechanical circuit, increasing capacitance and consequently lowering resonant frequency f. Independent monitoring of these resonant frequency shifts enables precise decoupling of both parameters. Zhang et al. implemented a complementary split-ring resonator (CSRR) on Al₂O₃ via screen printing (Figure e). When the incident signal frequency matches the cavity resonance, energy absorption peaks occur while nonresonant signals reflect. Increasing ambient temperature elevates the substrate’s dielectric constant, monotonically reducing resonant frequency. This planar architecture eliminates thermal expansion failures inherent in mechanical structures, significantly enhancing the high-temperature reliability. Islam et al. systematically optimized split-ring resonator (SRR) designs through parametric analysis (e.g., ring shape, radius, opening clearance, line width, etc.): (1) Circular SRRs demonstrated superior performance due to their homogeneous electromagnetic field distribution; (2) reduced ring radius increased unit-area capacitance and sensitivity; (3) opening gap variations showed minimal impact; and (4) wider ring lines enhanced capacitor area and sensing performance. Optimized SRRs thus enable high-temperature substance discrimination.

For scenarios where wireless signal capture proves to be challenging, wired active LC sensors incorporate adjustable AC excitation sources. By tuning excitation frequency to match the LC loop resonance (where impedance reaches minimum), frequency shifts precisely quantify measurands. This approach solves the problem that wireless passive LC sensing is difficult to capture signals in in specific applications, such as high-temperature pressure sensing scenarios. Tan et al. applied this approach in a 600 °C-capable alumina pressure sensor (Figure f) featuring a capacitive ″sandwich″ structure: pressure-induced cavity deformation reduces electrode spacing, increasing capacitance (C) and decreasing resonant frequationuency (f), enabling direct pressure quantification.

Hall Effect

The Hall effect provides a viable transduction mechanism for high-temperature sensors, operating on the principle shown in Figure g: When current traverses a conductor or semiconductor sheet (Hall element) under orthogonal magnetic fields, a transverse potential difference (Hall voltage) develops perpendicular to both current and magnetic field directions. − This enables the measurement of magnetic fields and currents in thermal environments. However, the high temperature environment intensifies carrier scattering and reduces mobility while altering critical material parameters including resistivity and carrier concentration, introducing a significant measurement drift. These challenges necessitate high-temperature resistant materials coupled with temperature compensation strategies for performance optimization.

Conventional silicon and indium arsenide Hall sensors suffer from thermal instability due to narrow bandgaps. In contrast, AlGaN/GaN heterostructure-based devices demonstrate superior high-temperature operation capabilities. , Kumar et al. fabricated Hall sensors by epitaxial growth of AlGaN/GaN heterostructures on silicon substrates, covering the operating temperature range of 75–500 K. Experiments have shown that the sensor is not sensitive to temperature changes. Ciuk et al. further developed a graphene-on-4H-SiC Hall sensor with a 100 nm alumina passivation layer, leveraging graphene’s double-carrier transport mechanism that maintains high carrier mobility at high temperatures. Critically, material microscopic defects induce variations in the intrinsic Hall voltages across sensors.

Magnetostrictive Sensing Principle

Magnetostriction constitutes a fundamental physical phenomenon wherein ferromagnetic materials exhibit dimensional changes (length/volume) under applied magnetic fields. − This effect enables magnetostrictive displacement sensors and level gauges with the operational principles illustrated in Figure h. A magnetostrictive waveguide core propagates current pulses that generate circumferential magnetic fields. Position magnets at measurement locations provide axial bias magnetic fields. Convergence of transient circumferential and static axial magnetic fields induces localized torsional deformation via the magnetostrictive effect, exciting torsional elastic waves propagating at constant acoustic velocity along the waveguide. A pickup coil at the excitation terminus detects the wave arrival timing. Given the torsional wave velocity (v) and measured time delay (Δt), the position magnet distance (d) is determined by d = vΔt/2. Critical to high-temperature operation is the magnetostrictive material’s Curie temperature (T _c). Ambient temperature exceeding T _c eliminates ferromagnetism and nullifies magnetostrictive effects.

Wang et al. investigated Fe₃₀Co₇₀, Fe₈₂Ga_13.5Al_4.5, and (Fe₈₃Ga₁₇)_99.4B_0.6 magnetostrictive alloys with elevated Curie temperatures. Position sensors fabricated from Fe₃₀Co₇₀ and Fe₈₂Ga_13.5Al_4.5 achieved 500 °C operation with a 2000 mm range and ±0.09 mm accuracy. Their innovative temperature sensing architectures include the following: (1) Monolithic design: Fe₃₀Co₇₀ waveguide cores utilize the temperature-dependent ultrasonic propagation velocity (v _T). By measuring the torsional wave transit time (t) between a fixed magnet and pickup coil, a linear correlation between temperature T and transit time t enables temperature measurement across 20–900 °C. (2) Bimetallic composite: For extreme environments up to 1200 °C, brazed junctions connect (Fe₈₃Ga₁₇) _99.4B_0.6 (torsional wave generation) and Gr₂₀Ni₈₀ (acoustic propagation) segments. While operating on identical wave transit principles, this configuration relaxes T _C requirements of the active material, extending the measurable range to 20–1200 °C.

Piezoelectric Sensing Principle

The piezoelectric effect comprises two fundamental modes: positive and inverse piezoelectric effects. − As shown in Figure i, the positive piezoelectric effect manifests as charge polarization in specific crystalline materials under mechanical stress, generating bound charges of opposite polarity on opposing surfaces. Charge polarity reverses with stress directionality and vanishes upon load removal, restoring electrical neutrality. , The inverse piezoelectric effect induces mechanical deformation upon application of electric fields. High-temperature operation imposes critical constraints to piezoelectric sensors: (1) Thermal stress generates spurious charge signals unrelated to mechanical stimuli; , (2) temperatures exceeding the Curie point T _c accelerate material aging and performance degradation. Consequently, piezoelectric sensor optimization requires the following: (1) selection of high Tc piezoelectric materials with operational limits below T _c/2; − (2) structural designs mitigating thermal stress interference; and (3) implementation of effective temperature compensation algorithms. Liu et al. demonstrated bismuth titanate (BTS) vibration sensors operating at 650 °C with less than 5% sensitivity drift. Zhang et al. achieved exceptional stability at 900 °C using YCOB (YCa₄O­(BO₃)₃) single-crystal accelerometers.

Seebeck Effect Sensing

The Seebeck effect constitutes the fundamental physical principle for high-temperature thermocouples and infrared thermopile sensors. As shown in Figure j, a closed circuit comprising two dissimilar conductors (or semiconductors) generates a thermal electromotive force (EMF) when junctions experience temperature differentials, arising from material-dependent thermoelectric potentials. , Measurement of this EMF enables quantification of junction temperature differences or absolute hot-junction temperatures. High-temperature viability relies on intrinsic material stability combined with protective strategies, including refractory sleeves, advanced coating, and microporous architectures, which mitigate thermal degradation. Thermocouples exemplify contact-based temperature sensors directly converting thermal signals, for temperature derivation via electronic processing. Conversely, infrared thermopiles sensor implement noncontact measurement through series-connected thermocouple arrays with ″hot″ junctions integrated into infrared-absorbing region membranes. , Target radiation absorption elevates absorber temperature, establishing ″hot–cold″ junction differentials that generate infrared-proportional EMF outputs. −

Standard thermocouples (Table ) exhibit distinct material combinations, operational temperature ranges, and Seebeck coefficients. In the aerospace field, K-type (NiCr-NiAl/Si) thermocouples are extensively deployed for engine health monitoring and fire detection systems, , while radiation-tolerant N-type (NiCrSi-NiSi) thermocouples support long-term space missions. During spacecraft re-entry, S-type (Pt10%Rh–Pt) thermocouples measure surface temperatures, , with B-types (Pt30%Rh–Pt6%Rh) monitoring rocket engine combustion chambers and thermal protection systems of supersonic vehicles. For hypersonic surface temperature measurements under high-speed airflow, traditional thermocouples exhibit significant errors and hysteresis due to flow-field interference from structural geometry and thermal inertia. Thin-film K-type thermocouples overcome this limitation through a minimized heat capacity and conformal mounting, substantially reducing measurement errors and hysteresis. In the metallurgical field, platinum rhodium armored B-type thermocouples withstand mechanical impact and wear in blast furnaces and heat treatment processes, maintaining accuracy under extreme mechanical/thermal stress. In the chemical industry, K-type thermocouples ensure operational safety in ethylene cracking reactors, preserving catalyst activity through precise temperature control. In the field of nuclear energy, Pt–Nb binary alloy-based thermocouples enable core temperature monitoring by synergizing radiation resistance with thermal stability.

1. Material Composition, Operational Temperature Range, Thermal EMF Characteristics, and Seebeck Coefficients of Representative Thermocouples.

thermocouple type	lead metal A (+)	lead metal B(−)	temperature range (°C)	EMF over the temperature range (mV)	Seebeck coefficient (μV/°C value at 0 °C)
J	iron	Kang Copper	–210∼1200	–8.095∼69.553	50.37
K	chromium–nickel	Alnico-manganese alloy	–270∼1370	–6.458∼54.886	39.48
T	copper	Kang Copper	–200∼400	–6.258∼20.872	38.74
E	chromium–nickel	Kang Copper	–270∼1000	–9.385∼76.373	58.70
S	platinum and 10% rhodium	platinum	–50∼1768	–0.236∼18.693	10.19
N	nickel/magnesium/silicon	nickel/magnesium/silicon	–270∼1300	–5.953∼55.786	26.16
B	30% platinum rhodium	6% platinum rhodium	0∼1800	0∼49.316	0.5

Thermal Resistance Sensing Mechanisms

Resistance temperature detectors (RTDs) operate through two distinct thermosensitive phenomena: positive temperature coefficient (PTC) and negative temperature coefficient (NTC) effects. The PTC effect manifests as increasing resistivity with rising temperature, while the NTC effect exhibits inverse resistivity-temperature dependence. , These opposing mechanisms underpin high-temperature thermistor sensors, where operational stability is derived from intrinsic material resilience enhanced by encapsulation technologies and circuit optimization. Thermistors primarily utilize semiconductor-ceramic composites whose resistance–temperature (R-T) properties originate from thermally induced band structure modifications that modulate carrier mobility. ,− Notably, NTC thermistors dominate high-temperature applications due to superior thermal cycling stability. Exemplifying this, the NTC thermistor prepared by Sahoo et al. developed CaTiO₃ nanocrystalline NTC thermistors achieving rapid response and enhanced sensitivity within 300–500 °C.

Challenges Faced by Different Measuring Principles at High Temperatures

The negative impact of high temperatures on sensor measurement performance is inevitable. Achieving high-precision measurements under such conditions necessitates a profound understanding of these effects and the development of mitigation strategies. Consequently, we systematically analyze the mechanisms through which high temperatures influence various sensing principles. For fiber Bragg grating sensors, high-temperature challenges primarily manifest in two aspects: (1) Thermal degradation of the refractive index modulation structure occurs in conventional FBGs exceeds 300 °C, progressively diminishing or erasing grating characteristics; and (2) temperature–strain cross-sensitivity complicates reflected wavelength variations due to parameter coupling, significantly compromising measurement accuracy. LC resonant sensors face three key challenges: (1) Substantially increased thermal noise disrupts signal stability and reduce accuracy; (2) elevated parasitic resistance at high temperatures causes signal attenuation; and (3) temperature-dependent resonant frequency drifts adversely affect measurement accuracy. , The magnetostrictive principle encounters challenges including: (1) thermal expansion-induced geometric distortion in magnetostrictive materials, which disrupts stress wave propagation paths and attenuates signals; and (2) altered electromagnetic field distribution characteristics in high-temperature environments, impairing signal generation and detection. Piezoelectric sensors exhibit critical limitations: (1) intensified electronic thermal motion reducing material resistivity and increasing leakage current, diminishing charge output efficiency; and (2) significant temperature-dependent drift of the piezoelectric coefficient. , The Seebeck (thermoelectric) principle is challenged by (1) oxidation of metal alloy thermoelectric materials in oxygen-containing high-temperature environments, where resultant oxide layers alter carrier concentration and lattice structure, resulting in Seebeck coefficient drift or failure; and (2) enhanced phonon scattering increasing material thermal conductivity (κ), thereby reducing the thermoelectric figure of merit. RTD confronts two primary issues: (1) the self-heating effect from Joule heating during current conduction causes sensor temperature to exceed ambient temperature, yielding erroneously high readings; and (2) characteristically large thermal inertia impedes rapid and accurate dynamic temperature measurement.

Signal Transmission in High-Temperature Sensors

High-temperature sensors are categorized into wired and wireless types based on signal transmission methodology. The selection between these modalities depends on factors including sensor operating principles, application environment requirements, and cost considerations. Wired sensing offers advantages such as high signal stability, rapid data transfer rates, and relatively low implementation and maintenance cost. Its limitations include restricted flexibility, complex installation wiring, and significant challenges in cabling deployment for scenarios involving extreme heat or moving components. Conversely, wireless sensors provide enhanced flexibility and simplified installation, rendering them particularly suitable for rotating components, confined spaces, or ultrahigh-temperature environments where physical wiring is impractical. However, this approach is susceptible to electromagnetic interference leading to signal attenuation and multipath effects, alongside higher equipment costs, and power consumption constraints, particularly for active configurations where battery life presents a significant challenge. − Critically, high-temperature environments impose severe demands on cables and connectors for wired systems. Under such conditions, wireless transmission often demonstrates distinct advantages.

FBG sensors inherently rely on fiber optic waveguides and are conventionally classified as wired devices. However, certain specific applications, such as rotating machinery, can achieve noncontact (wireless) optical signal coupling through implementations of optical collimators. For example, He et al. utilized this methodology (Figure ) to achieve real-time wireless temperature monitoring of compressor bearings. LC resonant sensors accommodate dual transmission modes: wireless sensing via electromagnetic field coupling and wired sensing through a direct excitation source connection. The operational principle of Hall sensors fundamentally necessitates both excitation current supply and wired Hall voltage signal readout, classifying them as wired active sensors requiring external power. When integrated into wireless systems, Hall sensors typically function solely as front-end signal acquisition units, with wireless transmission managed by dedicated communication modules. Traditionally, magnetostrictive sensors rely on physical cabling for excitation current delivery and echo signal reception, constituting a wired architecture. However, the integration of wireless transmission capabilities (through embedded transmitter modules) and IoT connectivity has emerged as a critical development trajectory for magnetostrictive sensors, especially within large-scale equipment or harsh operational environments.

4.

Schematic of optical wireless coupling for FBG signal propagation.

Reprinted (adapted or reprinted in part) with permission from ref . Copyright 2017, MDPI.

Compensation Systems for High-Temperature Sensors

The core function of the high-temperature compensation systems is to monitor ambient temperature in real time and dynamically adjust sensor output signals to effectively offset temperature-induced measurement inaccuracies. These systems fundamentally aim to ensure that sensors maintain a high measurement accuracy and long-term stability under high temperatures or wide thermal operating ranges. Current compensation technologies are categorized into software-based and hardware-based approaches. −

Software Compensation

Software compensation techniques primarily utilize correction of sensor outputs with curve fitting and neural network compensation representing established solutions.

Curve Fitting Method

This software compensation algorithm corrects sensor nonlinearities through mathematical modeling. Its core principle approximates the sensor’s input–output characteristic curve using specific mathematical functions (e.g., polynomials), thereby converting nonlinear responses into linear relationships. , Based on known calibration data, measurement accuracy is enhanced by optimizing polynomial order and determining optimal fitting curves via least-squares regression. While exhibiting strong adaptability for nonlinear compensation scenarios, the method’s efficacy critically depends on calibration data quality, and significant outliers can substantially degrade compensation performance. In addition, higher-order polynomial fitting with extensive data points may induce oscillatory behavior, resulting in nonmonotonic fitting curves and potential ill-conditioned equations. Figure illustrates a representative sensor curve fitting implementation. Guo et al. employed digital curve-fitting technology to compensate for high-temperature pressure sensors, and curve fitting under high-temperature environments can better enhance the measurement accuracy of the sensors.

5.

Algorithm workflow for sensor characteristic curve fitting

Neural Network Compensation

Neural network compensation leverages the powerful nonlinear mapping capabilities of artificial neural networks to model complex nonlinear characteristics in sensor systems. This approach operates by adjusting internal network weight parameters through training data, enabling effective compensation for systematic errors and external disturbances. , Backpropagation (BP) neural networks, representing a class of multilayer feedforward networks, are frequently employed for such error compensation. Within these networks, signal processing occurs via forward propagation (input layer → hidden layer → output layer), while error correction is achieved through backward propagation (output layer → hidden layer → input layer). The method iteratively minimizes the mean square error (MSE) between actual and desired outputs by iteratively adjusting weights and biases across hidden-to-output and input-to-hidden layers, as illustrated in Figure . Feng et al. successfully implemented BP networks to compensate for temperature drift in quartz crystal microbalance (QCM) humidity sensors, achieving a MSE reduction to 1 × 10^–4. However, standard BP networks face limitations, including susceptibility to local minima convergence and slow training speeds. Therefore, researchers have developed enhanced optimization algorithms such as improved sparrow search algorithm-optimized BP network (ISSA-BP), ant colony algorithm optimized BP network (ACO-BP), and genetic algorithm optimized BP network (GA-BP) for weight threshold adjustment.

6.

Structure diagram of the BP neural network.

Hardware Compensation

Hardware compensation technologies directly counter temperature influences through a physical layer design, encompassing two primary approaches: material optimization and temperature compensation circuitry. For material optimization, this method centers on selecting/designing materials with specific temperature characteristics or implementing specialized compensation structures to mitigate temperature-induced performance degradation in core sensing elements. The objective is to ensure high accuracy and stability across varying thermal conditions. Izu et al. demonstrated this in high-temperature oxygen sensors using CeZr₁₀ as sensing material paired with CeY₅₀ as compensation material. By optimizing the Y concentration in CeO₂–Y₂O₃, they identified matching resistance activation energies between CeY₁₀ and CeZr₅₀ with resistance values independent of oxygen partial pressure, achieving significant effect suppression across 773–1073 K.

Temperature Compensation Circuit Design

The temperature compensation counters temperature drift through specialized modules integrated into the signal conditioning circuit. Leakage current compensation circuits and bridge circuits represent two common prevalent compensations (Figure a). Leakage current compensation circuits exploit frequency differentials, component temperature characteristics, or parasitic effects to isolate leakage current components, generating counteracting currents or adjusting circuit parameters to precisely neutralize leakage impacts (Figure b). Nilsson et al. elevated circuit operating temperatures to 230 °C by incorporating collector-base and body-drain leakage compensation in Brokaw bandgap references, utilizing artificial leakage current sources to balance actual leakage currents. Bridge circuit compensation is based on Wheatstone bridge balance principles; this technique leverages interactions between bridge arm elements to compensate temperature-induced errors. As shown in Figure b, R ₁ denotes the active strain gauge (mounted on the measured component) while R _B represents the compensation strain gauge. With the changes, synchronous resistance changes in R ₁ and R _B during temperature variations induce differential outputs that counteract thermal effects. Two primary configurations exist: the compensation block method and the active element method. The compensation block method involves affixing the active strain gauge (R ₁) onto the measured structure, while the compensation strain gauge (R _B) mounts on a stress-free block matching the measured component’s material. Connected to adjacent bridge arms, thermal expansion-induced resistance changes mutually cancel temperature effects. For active element method, strategically oriented strain gauges in adjacent arms generate opposing resistance changes during temperature shifts (e.g., R ₁ tensioned and R ₂ compressed). This exploits material/installation orientation differences to nullify temperature artifacts in bridge output.

7.

Circuit compensation architectures. (a) Leakage current compensation schematic; (b) Wheatstone bridge configuration.

Challenges in Compensation System Implementation

The application of compensation systems in high-temperature sensors manifests limitations primarily through software and hardware approaches. Software compensation faces challenges in real-time performance, where computational latency induces compensation hysteresis under rapidly varying operational conditions. In addition, achieving precise synchronization in multichannel calibration proves difficult, with inherent constraints in dynamic tracking and rapid response capabilities. Hardware compensation methods, while providing direct real-time corrections, risk introducing ancillary measurement errors. Crucially, under extreme high-temperature environments, thermal degradation of compensation components themselves diminishes corrective efficacy.

Encapsulation of High-Temperature Sensors

High-temperature encapsulation constitutes a critical technology for ensuring long-term stability and reliable operation of sensors in extreme temperature environments. Its primary functions involve protecting core sensing elements from high-temperature corrosion, thermal deformation, and environmental degradation through strategic material selection and optimized structural design, thereby maintaining measurement accuracy and extending operational lifespan. Encapsulation quality directly determines the sensor performance and durability in high-temperature applications.

High-Temperature Encapsulation Materials

Selection of high-temperature encapsulation materials demands stringent requirements, including long-term high-temperature stability, mechanical robustness, environmental corrosion resistance, and thermal expansion coefficient (CTE) compatibility with sensing elements. Significant CTE mismatch induces excessive interfacial stress during thermal cycling, potentially causing deformation, interface crack propagation, or performance drift that severely compromises measurement accuracy. Predominant high-temperature encapsulation materials comprise metal alloys (e.g., nickel–iron alloys and nickel-based superalloys) and ceramics (e.g., alumina and silicon carbide). Among them, metal alloys offer superior mechanical strength, machinability, and thermal conductivity, though requiring consideration of their high-temperature oxidation and creep resistance. Nickel-based alloys are widely adopted for their exceptional high-temperature strength and oxidation resistance. Ceramic materials provide ultrahigh melting points, excellent chemical inertness, high-temperature stability, and electrical insulation. Design constraints include inherent brittleness and CTE management, with Al₂O₃ and SiC being prevalent choices.

Barrera et al. demonstrated FBG encapsulation using an alumina ceramic tube within a nickel alloy shell. Annealing at 1000 °C facilitated seed grating regeneration into recycled fiber Bragg gratings (RFBGs), enabling operation at 1000 °C with ±5 °C accuracy. Habisreuther et al. implemented sapphire fiber grating high-temperature strain sensors encapsulated in nickel–iron alloy tubes with high-temperature ceramic adhesives. Lyon and Di Marino emphasized CTE matching imperatives, noting that nonconfined regions (e.g., filler gaps) require low-viscosity materials to ensure complete infiltration and void prevention.

Encapsulation Structure

Encapsulation structures provide physical protection, environmental isolation, and mechanical support for sensitive components, signal processing circuits, and interconnects. These designs enhance overall reliability, measurement accuracy, and operational lifespan while suppressing external environmental disturbances, including thermal shock, chemical corrosion, and mechanical stress, ensuring performance stability under extreme thermal conditions. Common high-temperature encapsulation structures encompass tubular, solid-state isolated, substrate-mounted, and leadless encapsulation technologies.

Tubular Encapsulation

This simple and cost-effective approach enhances mechanical protection, reliability, and fatigue resistance in high-temperature sensors. Its typical bilayer design features: an inner core housing sensing elements (e.g., FBG or piezoresistive elements) and an outer layer protective sheath of high-temperature alloys or ceramics. This configuration effectively isolates sensors from harsh environments while providing robust mechanical integrity and corrosion resistance. As demonstrated by Izu et al., alumina ceramic tubes with Ni alloy shells encapsulating regenerated FBG sensors (Figure a) enable hysteresis-free operation at 1100 °C, achieving a thermocouple-comparable response time (9 s).

8.

High-temperature sensor encapsulation topologies. (a) Tubular hermetic packaging; (b) Solid-state isolated encapsulation with transfer media; (c) Sapphire FBG substrate-mounted configuration; (d) Type II dual-FBG triparameter sensor in stainless steel substrate; (e) Direct lead bonding (DLB) interconnect; (f) SKiN sintered leadless architecture; (g) Ceramic-embedded integration; (h) PCB-embedded multilayer assembly; (i) Siemens SiPLIT planar interconnect; (j) 2.5D heterogeneous integration.

reprinted with permission from ref . Copyright 2011, SPIE.

reprinted with permission from ref . Copyright 2002, UESTC.

reprinted with permission from ref . Copyright 2016, Habisreuther, T.

reprinted with permission from ref . Copyright 2021, IEEE.

reprinted with permission from ref . Copyright 2010, IEEE.

reprinted with permission from ref . Copyright 2023, Xi’an Microelectronic Technology Institute.

reprinted with permission from ref . Copyright 2019, IEEE.

reprinted with permission from ref . Copyright 2012, VDE Verlag.

Reprinted (adapted or reprinted in part) with permission from ref . Copyright 2017, IEEE.

Solid-State Isolated Encapsulation

Solid-state isolated encapsulation isolates sensitive components from aggressive media by using sealed cavities containing isolation diaphragms and transfer fluid (e.g., silicone oil). External pressure deforms the isolation diaphragm, transmitting force through incompressible fluid to sensing element for measurement. Zhang implemented this with a polysilicon high-temperature pressure sensor (Figure B): chip-glass anodic bonding formed the base, welded diaphragms created sealed cavities, and silicone oil injection through sealed ports achieved isolation. This configuration sustained long-term stable operation at 220 °C (250 °C) while maintaining excellent static characteristics.

Substrate Encapsulation

Substrate encapsulation bond sensor chips to high-temperature substrates with protective encapsulation provided physical shielding, environmental isolation, electrical interconnection, and mechanical support. For fiber optic sensors, substrate encapsulation uniquely enhances both thermal resilience and pressure sensitivity. Habisreuther et al. demonstrated sapphire FBG (SFBG) encapsulation (Figure c) through adhesive bonding within ceramic protective tubes and V-groove mounting on steel substrates, achieving stable operation at 600 °C with 1500 με strain capacity. Yao et al. designed stainless steel substrate-mounted FBGs via dual femtosecond laser engraving, enabling simultaneous temperature, strain, and vibration measurement at 1100 °C (Figure d). This configuration maintains undisturbed strain distribution while amplifying sensitivity 4-fold versus the bare grating.

Leadless Encapsulation Technology

Traditional wire bonding suffers from electromigration and thermal stress failures at high temperatures. Leadless encapsulation technology addresses these limitations through planar interconnect methods, including metal sintering, direct metallization, and embedding, significantly enhancing the high-temperature reliability. Key implementations include direct lead bonding (DLB), SKiN technology, embedded encapsulation, Siemens planar interconnect (SiPLIT), and 2.5D encapsulation. −

DLB employs copper straps to directly connect chip terminals (e.g., emitter, collector) to external pads (Figure e), eliminating bond wires to reduce parasitic inductance and interconnect resistance while improving electrical performance and reliability. Semikron’s SKiN technology utilizes double-layer flexible printed circuits (FPCs) with sintered connections (Figure f) to optimize electrical and thermal management in SiC power modules. Embedded encapsulation encompasses ceramic-based and PCB-based approaches: ceramic embedding integrates power chip within ceramic frames, where thin-film deposition (Ti/Cu seed layer) and electroplated Cu form interconnects and thermal paths (Figure g), demonstrating 75% lower parasitic inductance and 44% improved thermal resistance versus wire bonding. , PCB embedding inserts ultrathin chips into a multilayer board (Figure h), achieving low parasitic inductance, high power density, and reliability through shortened interconnects, thermal vias, and 3D stacking configurations. SiPLIT technology form interconnects via vacuum-laminated copper layers (50–200 μm) on insulating films (Figure i), with laser-ablated contacts in epoxy-clad laminates reducing parasitic inductance by 50% and thermal resistance by 20% through enhanced copper–chip contact. ,

The 2.5D encapsulation approach employs silicon interposers with through-silicon vias (TSVs) for multichip integration (Figure j), leveraging high-density routing and superior thermal pathways to enhance heat dissipation compared to traditional 2D packaging. ,

Challenges in Encapsulation for High-Temperature Sensors

High-temperature environments impose critical challenges on sensor encapsulation design. Significant material thermal expansion coupled with differential thermal expansion coefficients across encapsulation components induces localized stress concentrations. These stresses precipitate mechanical failures through mechanisms including bond-line fracture, solder joint cracking, and press-fit connection layer delamination. High temperatures also accelerate physical and chemical aging of polymeric encapsulants, sealants, and insulators, thereby compromising the long-term reliability. Concurrent thermal effects enhance interfacial material diffusion, degrading interface properties through increased contact resistance or diminished insulation performance, ultimately reducing encapsulation efficacy and potentially causing complete sensor failure. In addition, micron-scale sensing elements experience displacement during high-temperature assembly due to thermal expansion or stress relaxation, adversely impacting device accuracy and functionality.

Typical Applications for High-Temperature Sensors

High-temperature sensors deliver stable, reliable, and precise measurement capabilities in extreme thermal environments, establishing themselves as indispensable components in critical fields such as aerospace, automotive engineering, marine power systems, and industrial equipment. These sensors provide real-time and precise monitoring data for equipment operating under high-temperature environments, significantly enhancing operational safety, efficiency, and system reliability

For automotive applications, thermal sensors are extensively deployed in automotive systems, especially within powertrain and emission control subsystems. They continuously monitor the temperature, pressure, and other critical parameters during engine combustion, turbocharging, and exhaust processes, delivering precise feedback to engine control units for optimized control strategies. This ensures vehicle power performance, fuel efficiency, emission compliance, and long-term reliability. Operational resilience in harsh underhood environments characterized by extreme temperatures, vibrations, and chemical exposure is essential for these sensors. Figure illustrates representative installation locations for several critical high-temperature sensors in automotive powertrains.

9.

High-temperature sensor deployment in automotive powertrain systems.

Knock sensors embedded in engine blocks or cylinder heads employ piezoelectric ceramics to convert mechanical vibrations into electrical signals, operating at 130 °C to detect abnormal combustion events and trigger engine control unit (ECU)-mediated ignition timing adjustments. , Positioned within intake manifolds, turbocharger pressure sensor optimize boost efficiency through precise pressure monitoring, with standard variants rated for 130 °C while racing configurations withstand extreme temperatures up to 1000 °C. Cylinder pressure sensors mounted directly on cylinder heads monitor combustion chamber dynamics at operational temperatures reaching 135 °C. , For motion sensing, crankshaft position sensors located near crankshaft pulley or flywheel deliver position and rpm data within 120–150 °C ranges to coordinate ECU-controlled ignition and fuel injection, − while camshaft position sensors installed at camshaft fronts provide timing signals determining optimal ignition and fuel injection sequationuences, typically operating at a maximum temperature of 150 °C.

High-temperature sensors deployed in automobile exhaust systems primarily encompass oxygen sensors, nitrogen oxide sensors, and exhaust gas temperature sensors. Oxygen sensors are categorized as precatalytic oxygen sensors and postcatalytic oxygen sensors. , Among them, the precatalytic oxygen sensor, positioned upstream of the three-way catalytic converter, dynamically adjusts the air-fuel ratios by monitoring the exhaust oxygen content to optimize combustion efficiency. Conversely, the postcatalytic oxygen sensor downstream assesses catalytic converter efficacy. Both types utilize zirconia ceramic elements with platinum or palladium catalysts, operating within 300–800 °C temperature ranges. Nitrogen and oxygen sensors are strategically installed either flanking the catalytic converter or near the intake manifold, continuously detecting the NO _x concentrations to optimize combustion efficiency and reduce NO _x emissions. , Standard configurations withstand 105 °C in compact vehicles, while heavy-duty applications require 800 °C tolerance. Exhaust temperature sensors monitor critical zones, including the middle of the exhaust pipe, tailpipe termini, and catalytic converter surfaces to prevent thermal damage by triggering protective measures when exceeding 900 °C thresholds.

Aerospace Applications

High-temperature sensors constitute critical enabling technologies for aerospace systems, providing precise measurements of temperature, pressure, strain, and other parameters within extreme high temperature environments. Figure illustrates representative sensor installations in both aircraft and spacecraft configurations.

10.

Critical thermal sensing nodes in aerospace applications. (a) Aircraft propulsion monitoring points; (b) space shuttle main engine instrumentation.

In aircraft systems, diverse high-temperature sensors ensure operational safety. Engine turbines employ Type B thermocouples achieving sustained measurements at 1600 °C with peak tolerance to 1800 °C, , complemented by sapphire fiber optic high temperature sensor monitoring turbine blade surfaces at 1773K. Tail nozzle temperatures spanning 500∼900 °C utilize thermocouples or higher-accuracy sapphire fiber grating sensors for thermal monitoring. , Wing assemblies integrate sapphire fiber optic sensors for simultaneous strain, vibration and temperature measurement at 500 °C alongside dedicated heat flux sensor quantifying aerodynamic heating effects. ,

Spacecraft applications demand specialized sensing during launch and orbital operations. Rocket engine combustion chambers implement high-temperature laser sensors for geometric dimensioning and temperature mapping, while ceramic piezoelectric vibration sensors monitor structural dynamics. Engine turbine blade characterization employs laser-based dimensional analysis combined with temperature profiling via S-type thin-film thermocouples below 1250 °C, , whereas ITO thin-film thermocouples on Al₂O₃ ceramic substrates extend measurement capability to 1300 °C.

Marine Applications

Marine high-temperature sensors demand exceptional stability in extreme thermal, vibrational, and corrosive environments. Figure illustrates representative installations aboard vessels where power systems, exhaust networks, boilers, and steam circuits rely on such high-temperature sensors for critical parameter monitoring. Turbine installations employ K-type/S-type thermocouples or magneto-resistive sensors for exhaust gas temperature measurement, − complemented by 485 °C-rated vibration sensors eddy current displacement probes monitoring mechanical dynamics including shaft displacement and axial differential expansion. Within exhaust systems, platinum resistance thermometers (Pt100), K-type thermocouples, or infrared sensors quantify exhaust temperatures, while 800 °C-capable piezoelectric sensors concurrently analyze exhaust pulsation characteristics. Boiler combustion chambers utilize K-type/S-type thermocouples or platinum resistance sensors for thermal monitoring alongside 450 °C-rated vibrating level sensors, safeguarding water level limits. Steam turbine bearings integrate 485 °C-tolerant temperature-vibration sensors for condition monitoring, whereas steam distributors deploy 200 °C-rated pressure transmitters for real-time pressure measurement.

11.

Marine high-temperature sensing network for power and propulsion systems.

Industrial Field

High-temperature sensors also play a pivotal role in industrial manufacturing. In the metallurgical industry within industrial manufacturing, high-temperature sensors serve as the core temperature detection tools; in the power industry, they act as safeguards for the safety of energy equipment; and in the chemical industry, they function as precise controllers.

In the metallurgical industry, multiple thermocouples are employed internally to detect the temperature distribution within furnaces. These thermocouples are installed at key positions of blast furnaces, such as above the furnace shell, above the tuyeres, and at the lower charging ports (Figure a). This arrangement ensures comprehensive coverage of the positive pressure, neutral pressure, and negative pressure zones within the blast furnace, enabling real-time and effective feedback on the internal temperature conditions. Multiple thermocouples are also required in the continuous casting process in the metallurgical industry to ensure process stability and casting quality. They are primarily used for measuring the temperature of molten steel, continuous temperature measurement in tundishes, and temperature measurement and monitoring of molds (Figure b). The temperature measurement of molten steel necessitates precise and rapid measurement (completed within 4–6 s) to meet the timeliness requirements of steelmaking. Continuous temperature measurement in tundishes requires real-time recording of temperature changes to provide data support for adjusting the casting speed and selecting mold fluxes. Mold temperature measurement aims to ensure the quality of cast billets and to determine whether there is a breakout based on abnormal data.

12.

Schematic diagram of industrial classic equipment structure and installation positions of high-temperature sensors. (a) Schematic diagram of blast furnace structure and installation positions of high-temperature sensors; (b) schematic diagram of continuous casting process and installation positions of high-temperature sensors; (c) schematic diagram of continuous casting process and installation positions of high-temperature sensors; (d) schematic diagram of the reactor structure in the chemical industry and installation positions of high-temperature sensors.

In the power industry, common combustion furnaces in power plants frequently utilize thermocouples (such as Type K and Type S) and resistance temperature detectors (RTDs, such as Pt100) for temperature measurement, thereby achieving safety protection, efficiency optimization, and fault diagnosis. Thermocouples can measure temperatures up to 1300 °C or even higher, while RTDs typically measure temperatures up to around 600 °C. However, RTDs generally offer higher accuracy than thermocouples. Common transformers in the power industry often employ RTDs (Pt100) and fiber optic sensors to monitor the temperature distribution of transformers and predict potential faults in advance (Figure c). RTD sensors are relatively cost-effective but may suffer from interference in strongly electromagnetic environments. Nevertheless, fiber optic sensors can avoid such interference, enhancing measurement accuracy.

In the chemical industry, common reaction vessels frequently use RTDs (such as Pt100), thermocouples (such as Type K and Type J), and fiber optic sensors for temperature measurement to control the temperature and improve reaction efficiency. RTDs and thermocouples need to be placed directly inside the vessels for temperature measurement (Figure d). Although they provide accurate measurements, they are susceptible to corrosion damage from the medium. Therefore, corrosion-resistant materials are selected as protective layers, or coating protection is applied. Fiber optic sensors, with their advantages of immunity to electromagnetic interference and the ability to connect multiple measurement points to a single fiber, are suitable for high-pressure reaction vessels and complex reaction scenarios. Common cracking furnaces in the chemical industry often use thermocouples (such as Type K, Type E, and Type J) to monitor key local temperatures (such as the outlet temperature control of cracking furnaces). Meanwhile, the corrosion resistance of thermocouples must also be considered to prevent sensor damage caused by corrosive media.

Conclusion, Challenges, and Perspective

Conclusions

High-temperature sensor technology has evolved into a cohesive technical framework grounded in material innovation and synergistic multiprincipal development. High-temperature sensor performance is fundamentally governed by the thermal resilience of constituent materials, necessitating complementary strategies: precise temperature compensation to mitigate measurement principal deviations, coupled with advanced encapsulation to retard material degradation at high temperatures, collectively ensuring measurement accuracy in extreme thermal environments. This review synthesizes recent advances across five critical domains: material systems, sensing principles, compensation methodologies, signal transmission method, and encapsulation techniques.

Challenges

Material systems demonstrate progressive diversification, where traditional ceramics and metals maintain prominence while novel paradigms emerge. High-entropy alloys leverage entropy stabilization effects to achieve <1% aging drift over 1000 h, and wide-bandgap semiconductors suppress thermal carrier generation to extend operational temperature ranges beyond 600 °C. Sensing principles exhibit distinct thermal adaptation mechanisms: FBGs and LC resonance exploit inherent physical immunity to temperature interference; magnetostrictive and piezoelectric effects rely on Curie temperature optimization and structural engineering; Hall-effect sensors depend on high-temperature resistant materials and compensation circuits; thermoelectric (Seebeck) principles utilize alloy stability and protective architectures; while thermal resistance principle enhances accuracy through material innovation and encapsulation refinement. Temperature compensation technologies reveal critical trade-offs: traditional curve fitting accommodates diverse nonlinearities but suffers from calibration data dependency, with higher-order polynomials prone to oscillatory artifacts and ill-conditioned equationuations at scale. Neural network-based compensation addresses these limitations through powerful nonlinear mapping, reducing temperature drift errors to 10^–4 levels to effectively counteract systematic perturbations. Complementary hardware-level approaches, encompassing material optimization and compensation circuitry, directly mitigate thermal impacts on sensitive elements. Signal transmission presents distinct operational paradigms. Wired solutions offer stability and reliability but prove impractical in extreme thermal or dynamic scenarios due to inflexibility. Wireless transmission alternatives excel in rotating systems and confined spaces yet remain vulnerable to electromagnetic interference-induced signal attenuation and multipath effects. Encapsulation material selection prioritizes ceramic and alloy systems with stringent thermal expansion coefficient (CTE) matching to sensing elements. Structural configurations deliver specialized advantages: tubular designs dominate in thermal resistance, hermetic sealing, mechanical impact resistance, thermal conduction efficiency, and electromagnetic interference suppression. Solid-state isolation systems demonstrate superior high-temperature stability through optimized thermal management, achieving exceptional corrosion resistance alongside miniaturization and safety enhancements. Substrate-mounted package leverages high thermal conductivity for integrated anti-interference capabilities, deformation resistance, and impact tolerance. Leadless technologies excel in prolonged thermal endurance, environmental adaptability, and structural flexibility under extreme conditions, while 2.5D integration enables breakthrough thermal sharing, low-loss signal transmission, heterogeneous component integration, and system miniaturization.

Perspective

High-temperature sensors confront multiphysics failure mechanisms spanning thermal–mechanical–electrochemical domains: Critical issues include thermal expansion coefficient mismatches between refractory materials and sensor components; measurement principle degradation under thermal stress; electromagnetic interference in wireless transmission; temperature compensation latency and error propagation; interfacial diffusion at encapsulation boundaries; and material performance degradation in extreme environments. Future high-temperature sensor research should prioritize four interconnected domains: trans-temperature material stability, multiphysics coupling modeling, heterogeneous integrated encapsulation, and integrated sensing-storage-computing.

Trans-temperature Stability

This critical property denotes a material’s resistance to performance degradation (e.g., decomposition, deformation, strength loss) during thermal transients or wide operational ranges. Strategies to improve the stability of materials across temperature domains include alloying, surface engineering, heat treatment, and stabilizer addition. Alloying modulate crystalline configurations, phase composition, phase transformations, diffusion rate, and defect behavior. Surface engineering alters interfacial chemistry and microstructure. Heat treatment is for grain boundary optimization (e.g., phase composition, grain size, precipitated phase morphology and distribution, dislocation density, etc.). Stabilizer incorporation is to suppress deleterious phase transitions. Such interventions fundamentally address long-term stability under extreme cycling temperature conditions. It is a prerequisite for reliable sensor operation.

Multiphysics Coupled Modeling

As a holistic simulation framework, this methodology captures concurrent physical interactions through coupled mathematical representations of structural mechanics, fluid dynamics, electromagnetic fields, and heat transfer − Methods for multiphysics coupled modeling mainly include direct coupling and indirect coupling. Direct coupling solves unified equations within a single computational domain, while indirect coupling iteratively exchanges boundary data between physics-specific solvers. High-temperature sensors exhibit pronounced multiphysics interactions: (1) thermal expansion distorting pressure measurement accuracy, (2) electromagnetic Joule heating altering thermal profiles, and (3) material creep compromising structural stability. Therefore, effective multiphysics modeling of high-temperature sensors thus requires the following: temperature-dependent material characterization, physics interface coupling (e.g., COMSOL’s Joule Heating Module), and refined boundary conditions incorporating radiative-convective heat transfer. This foundation enables predictive optimization through parameter sensitivity analysis and closed-loop design validation.

Heterogeneous Integrated Encapsulation

As the cornerstone semiconductor technology in the post-Moore era, heterogeneous integration achieves system-level performance breakthroughs through copackaging diverse chips spanning multiple process nodes, material systems, and functionalities. This paradigm evolves through dimensional scaling: Conventional 2D integration arranges components horizontally on substrates with XY plane interconnects; 2.5D architectures employ silicon interposers to overcome bandwidth and power constraints of traditional 2D solutions; meanwhile, 3D stacking enables vertical (Z-axis) device integration with through-layer interconnections, yielding superior integration density and reduced power consumption. Although significantly minimizing signal transmission loss for high-temperature sensors, multichip stacking induces thermal management challenges including localized hotspots and thermal gradient amplification. , Advanced heat mitigation strategies such as embedded thermal vias, microfluidic cooling channels, and engineered thermal interface materials (TIMs) have become essential to ensure efficient heat dissipation.

Integrated Sensing–Storage–Computing

This architecture converges sensing, memory, and computational functions within unified systems, enabling high-efficiency, low-power, intelligent processing at the edge. By facilitating in situ data processing directly on sensors, it eliminates redundant data transfer while reducing system latency and power consumption, thereby enhancing edge response speed and intelligent decision-making capabilities. Implementation in high-temperature environments confronts multifaceted challenges: (1) Significant thermal expansion coefficient mismatches between sensor materials and memristor compounds (such as oxides and chalcogenides) provoke interfacial delamination or cracking; (2) accelerated ion migration in memristors above 150 °C degrades resistance uniformity (>20% drift error); (3) the concurrent presence of intense vibrational stresses and corrosive atmospheres in high-temperature environments necessitates synchronous multimodal signal processing, encompassing pressure, temperature, and chemical parameters, while existing memristor technologies remain fundamentally constrained to unimodal operation; (4) thermal runaway risks escalate due to computational unit efficiency collapse; and (5) multilayer interconnect reliability is compromised by the 280 °C melting point limitation of standard high-temperature solders (such as gold–tin alloys).

X.H. and H.W. contributed equally to this work. X.H.: Methodology investigation, Thesis research, Writing – original draft, and Writing – review and editing. B.S.: Writing – review and editing. Y.M.: Writing – review and editing. Z.Z.: Writing – review and editing. B.Y.: Writing – review and editing. L.Q.: Writing – review and editing. H.W.: Methodology, Supervision, and Writing – review and editing.

The authors declare no competing financial interest.