Defect engineering and enhancement of interfacial phonon scattering effects in La-doped SrTiO3 synthesized at high pressure and high temperature

Thermoelectrics (TE) have received a lot of attention for their ability to directly convert heat into electricity. This capability provides a promising solution for waste heat recovery and clean energy utilization. Strontium titanate (SrTiO 3 ) is a promising N-type oxide TE material. However, its practical application is limited by low electrical conductivity and high thermal conductivity. Here, we present a high-pressure synthesis technique aimed at simultaneously introducing defects as well as enhancing phonon scattering. Enhancing the thermoelectric properties of strontium titanate thermoelectric materials. SrTiO 3 samples doped with different concentrations of La were synthesized by high-pressure high-temperature (HPHT) synthesis, which effectively promotes the solid-phase reaction and thus allows for a more homogeneous and efficient doping of La atoms into the SrTiO 3 lattice as compared to the conventional synthesis method. The introduction of La 3+ creates a charge imbalance, which is compensated by the formation of oxygen vacancies. These oxygen vacancies act as donor defects, which in turn increase the carrier concentration and significantly improve the electrical conductivity of the samples. At the same time, the HPHT synthesis conditions induced severe lattice distortions, leading to grain refinement and the formation of dislocation networks and nanopores. By modulating the density and distribution of multiscale defects, La doping significantly improves the interfacial phonon scattering efficiency. This condition reduces the thermal conductivity and improves the thermoelectric properties. By combining defect engineering and interfacial phonon scattering, we achieved the decoupling of electrical and thermal transport properties in La-doped SrTiO 3 . Consequently, the thermoelectric figure of merit ( zT ) was significantly enhanced, reaching 0.18 at 973 K. This study introduces a new methodology and theoretical foundation for the development of high-performance oxide TE materials.