Realization of high thermoelectric performance in p-type unfilled ternary skutterudites FeSb2+xTe1-x via band structure modification and significant point defect scattering

FeSb2Te, a ternary derivative of binary CoSb3, displays anomalous electrical and thermal transport properties because of considerable modifications in the band structure induced by Fe and significant mixed valence state (namely Fe2+ and Fe3+) scattering of phonons. The substitution of Te for Sb generates more holes without notably affecting the band structure, while markedly improving the electrical conductivity and retaining a high Seebeck coefficient due to the enhanced density of states, thereby leading to dramatically increased power factors. Furthermore, the heat carrying phonons are strongly scattered with increasing x value because of the formation of solid solutions between two end members: square FeSb2Te and square FeSb3 (where square can be viewed as a vacancy). Consequently, high thermoelectric figures of merit were achieved in the FeSb2+xTe1-x compounds, with the largest ZT value reaching similar to 0.65 for the sample with x = 0.2. This is the highest value among all p-type unfilled skutterudites and is comparable with some filled compositions. Prospects for further improving the performance of p-type FeSb2Te-based skutterudites are discussed. Crown Copyright (C) 2013 Published by Elsevier Ltd. on behalf of Acta Materialia Inc. All rights reserved.