Medium-entropy (Sr_1/3Ba_1/3Ca_1/3)TiO₃ perovskite oxide for thermoelectric applications

A novel ternary medium-entropy perovskite oxide, (Sr_1/3Ba_1/3Ca_1/3)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 ZT_max 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.