Zr3NiSb7: a new anti­mony-enriched ZrSb2 derivative

V Romaka; A Tkachuk; L Romaka

doi:10.1107/S1600536808020278

. 2008 Jul 5;64(Pt 8):i47. doi: 10.1107/S1600536808020278

Zr₃NiSb₇: a new antimony-enriched ZrSb₂ derivative

V Romaka ^a,^*, A Tkachuk ^b, L Romaka ^a

PMCID: PMC2961902 PMID: 21202990

Abstract

Single crystals of trizirconium nickel heptaantimonide were synthesized from the constituent elements by arc-melting. The compound crystallizes in a unique structure type and belongs to the family of two-layer structures. All crystallographically unique atoms (3 × Zr, 1 × Ni and 7 × Sb) are located at sites with m symmetry. The structure contains ‘Zr₂Ni₂Sb₅’ and ‘Zr₄Sb₉’ fragments and might be described as a new ZrSb₂ derivative with a high Sb content.

Related literature

The structure of ZrSb₂ was described by Garcia & Corbett (1988 ▶). For related antimonides, see: Romaka et al. (2007 ▶); Tkachuk et al. (2007 ▶). For related literature, see: Emsley (1991 ▶).

Experimental

Crystal data

Zr₃NiSb₇
M _r = 1184.62
Orthorhombic,
a = 17.5165 (19) Å
b = 3.9266 (4) Å
c = 14.3968 (15) Å
V = 990.22 (18) Å³
Z = 4
Mo Kα radiation
μ = 23.56 mm⁻¹
T = 295 (2) K
0.37 × 0.06 × 0.04 mm

Data collection

Bruker SMART 1000 diffractometer
Absorption correction: numerical (SHELXTL; Sheldrick, 2008 ▶) T _min = 0.057, T _max = 0.426
11118 measured reflections
1722 independent reflections
1500 reflections with I > 2σ(I)
R _int = 0.043

Refinement

R[F ² > 2σ(F ²)] = 0.024
wR(F ²) = 0.053
S = 1.18
1722 reflections
68 parameters
Δρ_max = 2.12 e Å⁻³
Δρ_min = −2.89 e Å⁻³

Data collection: SMART (Bruker, 2000 ▶); cell refinement: SAINT-Plus (Bruker, 2000 ▶); data reduction: SAINT-Plus; program(s) used to solve structure: SHELXS97 (Sheldrick, 2008 ▶); program(s) used to refine structure: SHELXL97 (Sheldrick, 2008 ▶); molecular graphics: DIAMOND (Brandenburg, 1999 ▶); software used to prepare material for publication: SHELXL97.

Supplementary Material

Crystal structure: contains datablocks I, global. DOI: 10.1107/S1600536808020278/wm2182sup1.cif

e-64-00i47-sup1.cif^{(27.7KB, cif)}

Structure factors: contains datablocks I. DOI: 10.1107/S1600536808020278/wm2182Isup2.hkl

e-64-00i47-Isup2.hkl^{(84.9KB, hkl)}

Additional supplementary materials: crystallographic information; 3D view; checkCIF report

Table 1. Selected bond lengths (Å).

Zr1—Sb4ⁱ	2.9620 (6)
Zr1—Sb6	2.9876 (8)
Zr1—Sb1ⁱⁱ	3.0669 (8)
Zr1—Sb3ⁱⁱⁱ	3.0720 (7)
Zr1—Sb7ⁱⁱⁱ	3.0960 (6)
Zr1—Sb5	3.1324 (8)
Zr2—Sb6^iv	2.9478 (6)
Zr2—Sb4ⁱⁱⁱ	2.9499 (6)
Zr2—Sb2^iv	2.9604 (6)
Zr2—Sb2ⁱⁱ	3.0029 (8)
Zr2—Sb5	3.0044 (8)
Zr3—Sb1^iv	2.9569 (6)
Zr3—Sb3^iv	2.9944 (7)
Zr3—Sb5^iv	2.9958 (6)
Zr3—Sb6^v	2.9975 (8)
Zr3—Sb3^vi	3.1616 (9)
Ni1—Sb7	2.5728 (10)
Ni1—Sb2^iv	2.5875 (7)
Ni1—Sb1^iv	2.6140 (7)
Ni1—Sb4^vi	2.7141 (10)
Sb1—Sb2	3.1998 (8)
Sb1—Sb3^vii	3.2645 (6)
Sb1—Sb4^viii	3.2981 (6)
Sb2—Sb2^ix	3.2250 (7)
Sb2—Sb4^viii	3.3111 (6)
Sb5—Sb7ⁱⁱⁱ	3.1380 (6)
Sb5—Sb6^iv	3.1387 (6)
Sb6—Sb7ⁱ	3.1393 (6)

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Symmetry codes: (i) Inline graphic ; (ii) ; (iii) ; (iv) ; (v) ; (vi) ; (vii) ; (viii) ; (ix) .

Acknowledgments

The work was in part supported by the Ministry of Ukraine for Education and Science (grant No. 0106U001299).

supplementary crystallographic information

Comment

Antimony based intermetallics attract interest due to interesting thermoelectric properties of some phases, e.g. antimonides with MgAgAs and Y₃Au₃Sb₄ type structures. The investigation of new intermetallic phases is useful for the development of new materials, and the accurate determination of their crystal structures is a basic requirement for a better understanding of the corresponding physical properties.

Investigation of the Zr–Ni–Sb ternary system revealed the presence of several compounds in the Sb-enriched area (Romaka et al., 2007), including the new title antimonide with composition Zr₂₇Ni₉Sb₆₄ (in %_at). Interatomic distances (Table 1) between Sb atoms are in good agreement with the sum of the atomic radius (Emsley, 1991), whereas the majority of Zr—Sb and all Ni—Sb distances are somewhat shortened. Such shortening may be explained by partial covalent bonding which appears to be significant between Ni—Sb atoms because their contact distances are rather close to the sum of their covalent radii (2.56 Å). As the majority of ternary intermetallics are constructed from the fragments of their most stable binary compounds, the structure analysis of the antimonides Zr₃NiSb₇ and the already known Zr₂NiSb₃ (Tkachuk et al., 2007) in the Sb-enriched area shows that both can be derived from the binary compound ZrSb₂ (Garcia & Corbett, 1988), which crystallizes in the PbCl₂ structure type.

Zr₃NiSb₇ belongs to the family of two-layer structures. It may be represented as a net of trigonal prisms formed by Sb atoms that are bridged by nickel atoms (Fig. 1a). Such an arrangement is very similar to that in the binary ZrSb₂ structure (Fig. 1b). The coordination polyhedra are distorted tri-capped trigonal prisms for the Zr atoms, and distorted octahedra for Ni atoms. In an alternative description, the Zr₃NiSb₇ structure contains fragments of the hypothetical "Zr₂Ni₂Sb₅" and "Zr₄Sb₉" structures (Fig. 2) which are so far unknown for the ternary Zr–Ni–Sb or binary Zr–Sb systems. The main feature of the Zr₃NiSb₇ structure is the absence of covalent bonding between antimony atoms in contrast to the ZrSb₂ structure. The general conclusion is that the presence of Ni atoms intensifies the interaction between Zr/Ni and Sb and, at the same time, reduces the bonding between Sb atoms. One may speculate that the composition of the Zr₃NiSb₇ compound may be the boundary limit of some solid solutions based on ZrSb₂. However, the detailed study of the phase equilibria in the Zr–Ni–Sb system did not show a formation of any substitutional or interstitial solid solution. Moreover, the diffraction patterns of Zr₃NiSb₇ and ZrSb₂ are rather different.

Experimental

A sample with nominal composition Zr₃₀Ni₁₀Sb₆₀ was prepared by arc-melting the constituent elements Zr (99.99 wt.%), Ni (99.99 wt.%), and Sb (99.99 wt.%) on a water-cooled copper hearth under a protective Ti-gettered argon atmosphere. 5 wt.% excess of Sb was required to compensate the evaporative loss during arc-melting. The ingot was annealed at 870 K for 720 h in an evacuated silica ampoule, and finally quenched in cold water. A crystal of the title compound suitable for single-crystal X-ray diffraction was extracted directly from the annealed sample. The chemical composition of the crystal was determined on the basis of an energy dispersive X-ray spectroscopical analysis using a Hitachi S-2700 scanning electron microscope. The result of the analysis is in good aggreement with the composition calculated from the structural refinement: Measured: 24.5 (8) %_at Zr, 11.3 (6) %_at Ni, 64.2 (16) %_at Sb; calculated Zr 27 %_at, Ni 9%_at, Sb 64 %_at.