Thermoelectric Characterization of Zone-Melted and Quenched Zn4Sb3

Because of its complex structure, Zn₄Sb₃ exhibits relatively low thermal conductivity. This, in combination with large values of the Seebeck coefficient and moderate to high electrical conductivity, makes the material especially interesting for thermoelectric application in temperatures up to 400°C. The phase purity and thermal stability of Zn₄Sb₃ are major issues for its thermoelectric performance and are strongly dependent on the synthesis method, atmosphere, density, and grain size. Therefore, Zn₄Sb₃ was prepared by both zone melting and quenching in this study, and pressed samples from crushed powders of three different grain sizes were compared. The effect of thermal cycling was studied, along with repeated structural analysis and Seebeck mapping. It was found that zone melting leads to improved thermal stability regarding decomposition via Zn loss, which finally may result in the formation of ZnSb. Larger grain size seems to reduce the degradation, because of lower concentration of grain boundaries, thus hindering diffusion inside the material.