High-temperature thermoelectric properties of (1 − x) SrTiO₃ − (x) La_1/3NbO₃ ceramic solid solution

Ceramics based on SrTiO₃ are of growing interest as thermoelectric materials because of their high-temperature stability and non-toxicity. Substitution of La and Nb into the perovskite structure provides opportunities to control both the microstructure and properties. Ceramic solid solutions of (1 − x) SrTiO₃ − (x) La_1/3NbO₃ were prepared by the mixed oxide route, using compositional steps of x = 0.1. Pressed pellets were sintered at temperatures of 1573 K to 1723 K in air. Addition of aliovalent ions (La³⁺, Nb⁵⁺) on the A/B sites (Sr²⁺, Ti⁴⁺) led to A-Site cation deficiency in the stoichiometric compositions and other defect structures which increased carrier concentration. A maximum ZT of 0.004 was obtained for the x = 0.2 stoichiometric sample, although much higher ZT values are possible by sample reduction.