Enhanced thermoelectric performance of Sr0.875La0.1TiO3-δ based composites through Bi-rich inclusions in internal and external reduction environments

The electrical transport performance of bulk SrTiO3 thermoelectric materials can be optimized by incorporating uniformly dispersed conductive inclusions. Herein, the impact of Bi2O3 addition on the thermoelectric properties of La-doped strontium titanate composite nano Ti powder (Sr0.875La0.1TiO3-δ/20 wt% Ti) has been examined. During the sintering process, Bi2O3 gradually transforms into a liquid phase to facilitate Redox reactions with nano Ti and mass transfer, followed by reduction and transformation into Bi–Bi2O3 particles that precipitate at grain boundaries. The presence of nanoscale Bi-rich phases reduces carrier transport barriers at grain boundaries and enhances phonon relaxation time associated with grain boundary scattering. Ultimately, the sample containing 10 wt% bismuth oxide exhibits the lowest lattice thermal conductivity and the highest weighted mobility. This led to a maximum power factor of 498 μW/mK2 at 873 K and a maximum ZT value of 0.188 at 1073 K. This study presents a novel approach to decouple electroacoustic transport through the utilization of Redox reactions between multiple phases, offering valuable insights for the development of high-performance thermoelectric oxide composites.