Strontium titanate-based ceramics processed by laser floating zone: Effects of processing atmosphere and Sr/Ti ratio

Strontium titanate (SrTiO 3 ) is a well-known perovskite oxide with a simple crystalline structure and well-documented redox sensitivity, making it a versatile material for a wide range of functional applications, including thermoelectrics, photocatalysis and electronics. In this work, SrTiO 3 -based ceramics with varied Sr/Ti ratios (Sr 0.95 TiO 3-δ , SrTiO 3-δ , and Sr 1.05 TiO 3±δ ) were processed using the laser floating zone (LFZ) technique under oxidising and reducing atmospheres, enabling a controlled study of the effects of non-equilibrium processing conditions on phase composition and microstructure. Despite the simplicity of the system, the combination of LFZ and composition variation led to pronounced changes in phase evolution behaviour, grain morphology, and local structural order. Secondary phase segregation, including TiO 2 and SrO, was observed to depend on stoichiometry and processing atmosphere, with some precipitates showing preferred orientation along the growth direction. Raman spectroscopy revealed distinct signatures of lattice distortion in air-processed samples, in contrast to the more symmetric structures formed under reducing conditions. The thermogravimetric analysis confirmed the formation of only minimal Ti 3+ , underscoring the need for further defect engineering strategies to achieve functional properties such as enhanced electronic conductivity. These results highlight the potential of LFZ processing, combined with tailored composition, as a versatile tool for tuning the microstructure of SrTiO 3 -based ceramics for various functional applications.