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Unexpected High-Temperature Stability of β-Zn4Sb3 Opens the Door to Enhanced Thermoelectric Performance

Lin, Jianping, Li, Xudong, Qiao, Guanjun, Wang, Zhao, Carrete, Jesús, Ren, Yang, Ma, Lingzhi, Fei, Youjian, Yang, Baifeng, Lei, Lei, Li, Ju
Journal of the American Chemical Society 2014 v.136 no.4 pp. 1497-1504
molecular dynamics, temperature, thermal conductivity, zinc
β-Zn₄Sb₃ has one of the highest ZT reported for binary compounds, but its practical applications have been hindered by a reported poor stability. Here we report the fabrication of nearly dense single-phase β-Zn₄Sb₃ and a study of its thermoelectric transport coefficients across a wide temperature range. Around 425 K we find an abrupt decrease of its thermal conductivity. Past this point, Zn atoms can migrate from crystalline sites to interstitial positions; β-Zn₄Sb₃ becomes metastable and gradually decomposes into Zn(hcp) and ZnSb. However, above 565 K it recovers its stability; in fact, the damage caused by decomposition can be repaired completely. This is key to its excellent thermoelectric performance at high temperature: the maximum ZT reaches 1.4. Molecular dynamics simulations are used to shed light on the microscopic behavior of the material.