Solvothermal synthesis of La9.33Si6O26 nanocrystals and their enhancing impacts on sintering and oxygen ion conductivity of Sm0.2Ce0.8O1.9/La9.33Si6O26 composite electrolytes

La9.33Si6O26 (LSO) nanocrystals, quasi-spherical in shape and of an average size ca. 45 nm, were synthesized via a solvothermal process and used to mix with Sm0.2Ce0.8O1.9 (SDC) ultrafine powder to fabricate SDC-LSO composite electrolytes for the applications in IT-SOFCs. The microstructures and phase components of LSO nanocrystals and SDC-LSO composite electrolytes were characterized by XRD, TEM and HRTEM and, in particular, the sintering performance and oxide ion conductivity of SDC-LSO composites with different SDC/LSO volume ratios were studied. It has been found that the LSO nanocrystals are homogeneously dispersed in the as-sintered SDC-LSO composites and no impurity phases due to chemical reactions can be detected between SDC and LSO particles by XRD, but the sintering performance is remarkably improved with a temperature reduction by 100-250 °C, compared to that for the individual constituent phases. Moreover, the oxide ions conductivity of SDC-LSO composites can be conspicuously enhanced with the sample SL7525 (SDC/LSO = 0.75/0.25) showing the highest enhancement by 118%, i.e. 1.62 times that of SDC at 800 °C. The SDC/LSO hetero-interfaces with high energy and appropriate residual thermal stresses in the SDC-LSO composite microstructures are considered responsible for their improved sintering performance and significant enhancements in oxide ions conductivity.