Microstructure and thermoelectric properties of Sr_0.9La_0.1TiO₃/TiO₂ biphase composite ceramics

As a well-known n-type perovskite thermoelectric oxides, SrTiO₃ has always captured attention to find strategies for achieving high thermoelectric performance. In this paper, a series of reduced Sr_0.9La_0.1TiO₃/TiO₂ biphase composite ceramics were prepared via the solid-state reaction method. The effects of TiO₂ on the microstructure and thermoelectric properties of the ceramics were investigated. The addition of TiO₂ enhanced the carrier mobility via the formation of A-site cation vacancies and increased the carrier concentration probably through introducing oxygen vacancies in rutile TiO₂ during the reduction process. Moreover, the additional phonon scattering provided by the interface between the second phase and matrix and oxygen vacancies decreased the thermal conductivity. When the TiO₂ addition ratio was optimized to 25 wt%, a large power factor of 1.66 mW/K²/m and the ZT value of 0.24 were achieved at 447 K. The present strategy in this work may be feasible to broaden the range of operating temperature of SrTiO₃-based oxide thermoelectric materials.