Role of phonon scattering by elastic strain field in thermoelectric Sr1−xYxTiO3−δ

Perovskite-type SrTiO3−δ ceramics are multifunctional materials with significant potential as n-type thermoelectric (TE) materials. The electronic and thermal transport properties of spark plasma sintered polycrystalline Sr1−xYxTiO3−δ (x = 0.05, 0.075, 0.1) ceramics are systematically investigated from (15–800) K. The Sr0.9Y0.1TiO3−δ simultaneously exhibits a large Seebeck coefficient, α > −80 μV/K and moderately high electrical resistivity, ρ ∼ 0.8 mΩ-cm at a carrier concentration of ∼1021 cm−3 at 300 K resulting in a high TE power factor defined herein as (α2σT) ∼ 0.84 W/m-K at 760 K. Despite the similar atomic masses of Sr (87.6 g/mol) and Y (88.9 g/mol), the lattice thermal conductivity (κL) of Sr1−xYxTiO3−δ is significantly reduced with increased Y-doping, owing to the smaller ionic radii of Y3+ (∼1.23 A, coordination number 12) compared to Sr2+ (∼1.44 A, coordination number 12) ions. In order to understand the thermal conductivity reduction mechanism, the κL in the Sr1−xYxTiO3−δ series are phenomeno...