Synthesis, Structure, and Thermoelectric Properties of α-Zn₃Sb₂ and Comparison to β-Zn₁₃Sb₁₀

Abstract

Zn–Sb compounds (e.g., ZnSb, β-Zn13Sb10) are known to have intriguing thermoelectric properties, but studies of the Zn3Sb2 composition are largely absent. In this work, α-Zn3Sb2 was synthesized and studied via temperature-dependent synchrotron powder diffraction. The α-Zn3Sb2 phase undergoes a phase transformation to the β form at 425 °C, which is stable until melting at 590 °C. Rapid quenching was successful in stabilizing the α phase at room temperature, although all attempts to quench β-Zn3Sb2 were unsuccessful. The structure of α-Zn3Sb2 was solved using single crystal diffraction techniques and verified through Rietveld refinement of the powder data. α-Zn3Sb2 adopts a large hexagonal cell (R 3̅ space group, a = 15.212(2), c = 74.83(2) Å) containing a well-defined framework of isolated Sb3– anions but highly disordered Zn2+ cations. Dense ingots of both the α-Zn3Sb2 and β-Zn13Sb10 phases were formed and used to characterize and compare the low temperature thermoelectric properties. Resistivity and Seebeck coefficient measurements on α-Zn3Sb2 are consistent with a small-gap, degenerately doped, p-type semiconductor. The temperature-dependent lattice thermal conductivity of α-Zn3Sb2 is unusual, resembling that of an amorphous material. Consistent with the extreme degree of Zn disorder observed in the structural analysis, phonon scattering in α-Zn3Sb2 appears to be completely dominated by point-defect scattering over all temperatures below 350 K. This contrasts with the typical balance between point-defect scattering and Umklapp scattering seen in β-Zn13Sb10. Using the Debye–Callaway interpretation of the lattice thermal conductivity, we use the differences between α-Zn3Sb2 and β-Zn13Sb10 to illustrate the potential significance of cation/anion disorder in the Zn–Sb system.

How to Look for Compounds: Predictive Screening and in situ Studies in Na−Zn−Bi System

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“…The subset of Zintl phases with complex unit cells gives rise to more phonon modes leading to increased phonon scattering and lower thermal conductivity. Examples of such materials include Yb 14 MnSb 11 , 2,3 Zn-Sb phases, 4,5,6 and Tl 2 Ag 12 Te 7+δ . 7 Other optimization strategies include: electronic structure modification (e.g.…”

Structural evolution in thermoelectric zinc antimonide thin films studied by in situ X-ray scattering techniques

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