Medium-entropy (Sr1/3Ba1/3Ca1/3)TiO3 perovskite oxide for thermoelectric applications

Abstract

A novel ternary medium-entropy perovskite oxide, (Sr1/3Ba1/3Ca1/3)TiO3, is reported for thermoelectric applications; it was synthesized via solid-state reaction and graphite burial sintering. The formation and stability of the single-phase structure were evaluated using thermodynamic calculations and the Goldschmidt’s tolerance factor. The material was found to have a single-phase cubic perovskite structure with a homogeneous distribution of all elements. The medium entropy generates moderate carrier mobility, while the band flattening yields high Seebeck coefficient, resulting in a high power factor of 378.8 μW·m−1·K−2 at 773 K. The enhanced multi-phonon scattering derived from the medium entropy, oxygen vacancies, and porous structure significantly reduced the lattice thermal conductivity, with a lowest value of 1.90 W·m−1·K−1 at 773 K. As a result, a ZTmax of 0.13 was attained at 773 K, which outperforms that of high-entropy SrTiO3-based oxides. This work provides a new direction to obtain high-performance thermoelectric materials through medium-entropy composition design.