Ternary Zinc Antimonides Unlocked Using Hydride Synthesis.

Three new sodium zinc antimonides NaZnSb, NaZnSb, and NaZnSb were synthesized utilizing sodium hydride NaH as a reactive sodium source. In comparison to the synthesis using sodium metal, salt-like NaH can be ball-milled, leading to the easy and uniform mixing of precursors in the desired stoichiometric ratios. Such comprehensive compositional control enables a fast screening of the Na-Zn-Sb system and identification of new compounds, followed by their preparation in bulk with high purity. NaZnSb crystallizes in the triclinic 1 space group (. 2, 2, = 8.8739(6) Å, = 10.6407(7) Å, = 11.4282(8) Å, α = 103.453(2)°, β = 96.997(2)°, γ = 107.517(2)°) and features polyanionic [ZnSb] clusters with unusual 3-coordinated Zn atoms. Both NaZnSb ( 4, = 28.4794(4) Å, = 4.47189(5) Å, = 17.2704(2) Å, β = 98.3363(6)°) and NaZnSb ( = 8, = 32.1790(1) Å, = 4.51549(1) Å, = 9.64569(2) Å, β = 98.4618(1)°) crystallize in the monoclinic 2/ space group (. 12) and have complex new structure types. For both compounds, their frameworks are built from ZnSb distorted tetrahedra, which are linked via edge-, vertex-sharing, or both, while Na cations fill in the framework channels. Due to the complex structures, NaZnSb and NaZnSb compounds exhibit low thermal conductivities (0.97-1.26 W·m K) at room temperature, positive Seebeck coefficients (19-32 μV/K) suggestive of holes as charge carriers, and semimetallic electrical resistivities (∼1.0-2.3 × 10 Ω·m). NaZnSb and NaZnSb decompose into the equiatomic NaZnSb above ∼800 K, as determined by synchrotron powder X-ray diffraction. The discovery of multiple ternary compounds highlights the importance of judicious choice of the synthetic method.