Thermoelectric Properties of n-type CaTiO3, SrTiO3 and BaTiO3

Mitigating anthropogenic climate change requires a package of technologies including methods to enhance the efficiency of the energy-intensive transportation and industry sectors. Thermoelectric (TE) power, which harnesses the Seebeck effect in a TE material to extract electrical energy from a temperature gradient, is a proven technology that could meet this need. Oxide-based TEs are desirable due to their low cost, high chemical stability, and low toxicity, but are generally limited by a low electrical conductivity and high thermal conductivity. In this study, we employ a fully ab initio approach to study the electrical and thermal transport and thermoelectric figure of merit ZT of the oxide perovskites CaTiO3, SrTiO3 and BaTiO3. We predict that carrier concentrations of n ≈ 10^21 cm^−3 are required to optimise the thermoelectric power factor, and the piezoelectric scattering in rhombohedral BaTiO3 limits the electrical conductivity compared to the other two systems. We find that the lattice thermal conductivity κlatt is primarily determined by the structure type and chemical bonding through the phonon group velocities. We predict that CaTiO3 and SrTiO3 can achieve ZT > 1 at high temperature, and that the ZT of SrTiO3 could be further enhanced by the impact of doping or alloying to obtain the required n on the κlatt. The favourable comparison to experimental measurements suggest that this modelling approach has considerable predictive power, and could therefore serve as a valuable complement to experiments to identify new high-performance oxide TEs.