Thermoelectric properties of the low-spin lanthanide cobalate perovskites LaCoO3, PrCoO3, and NdCoO3 from first-principles calculations

Abstract

An ab initio modelling workflow is used to predict the thermoelectric properties and figure of merit ZT of the lanthanide cobalates LaCoO₃, PrCoO₃ and NdCoO₃ in the orthorhombic Pnma phase with the low-spin magnetic configuration. The LnCoO₃ show significantly lower lattice thermal conductivity than the widely-studied SrTiO₃, due to lower phonon velocities, with a large component of the heat transport through an intraband tunnelling mechanism characteristic of amorphous materials. Comparison of the calculations to experimental measurements suggests the p-type electrical properties are significantly degraded by the thermal spin crossover, and materials-engineering strategies to suppress this could yield improved ZT. We also predict that n-doped LnCoO₃ could show larger Seebeck coefficients, superior power factors, lower thermal conductivity, and higher ZT than SrTiO₃. Our results highlight the exploration of a wider range of perovskite chemistries as a facile route to high-performance oxide thermoelectrics, and identify descriptors that could be used as part of a modelling-based screening approach.