Table 1.

Deposition techniques, operating temperatures, and gas sensitivity of α-Fe₂O₃-based, NO₂ sensors reported in literature.

Material	Target Gas	Operating Temperature (°)	Tested Gases	Preparation Technique	Response to NO2 (ΔR/R0)%	Ref.
α-Fe2O3	NO2	200	NO2, H2S, acetone methanol, NH3	Sol-gel	17.2 (200 ppm)	[22]
α-Fe2O3	Ethanol	225	NO2, CO, acetone, CO2, NH3, H2, O2	Sol-gel	90 (100 ppm)	[36]
Polypyrrole/α-Fe2O3	NO2	200	NO2, NH3, ethanol, H2S, methanol, Cl2	Sol-gel	54 (100 ppm)	[37]
graphene/α-Fe2O3	NO2	120	NO2	Hydrothermal	8.2 (5 ppm)	[38]
α-Fe2O3	NO2	200	NO2, H2S, acetone methanol, NH3	Spray pyrolysis	17.2 (200 ppm)	[39]
α-Fe2O3	NO2	200	NO2, CO, CO2	Hydrothermal	59.9 (1 ppm)	This work