Thermoelectric performance enhancement in Sr0.9La0.1TiO3-based ceramics by high-pressure, high-temperature treatment

As an oxide thermoelectric material, the adjustment of oxygen vacancy plays an important role in strontium titanate (SrTiO3). Traditional synthesis methods typically necessitate post-synthesis reduction annealing to optimize its electrical properties. However, the oxygen vacancy concentration of samples synthesized by this approach may be distributed in a gradient manner. In this study, a high-temperature and high-pressure (HPHT) synthesis treatment was adopted, incorporating titanium powder into the raw material. This novel approach leverages the closed environment created by high pressure and the robust oxygen-trapping capabilities of titanium powder at elevated temperatures. It resulted in enhanced electrical properties in synthesized samples without the need for reduction annealing. Building upon this achievement, we successfully synthesized SrTiO3 samples doped with lanthanum (La) at different pressures. The sample synthesized at 5GPa demonstrated an optimal zT value of 0.22 at 973 K. This work provides a novel approach to the effective synthesis and improved electrical properties of strontium-based thermoelectric materials.