Low temperature synthesis of pure SrSnO₃ and the (Ba_xSr_1-x)SnO₃ solid solution by the polymerized complex method

Pure SrSnO₃ and (Ba_1-xSr_x)SnO₃ with compositions (x = 0, 0.25, 0.5, 0.75 and 1) were directly prepared by the polymerized complex (PC) technique based on a modified Pechini-type reaction route at the relatively low temperature of 600°C. Anhydrous citric acid (CA) was added to SnCl₄.xH₂O dissolved in ethylene glycol (EG). After complete dissolution, BaCO₃ and SrCO₃ powders were added according to the desired mole ratio of the solid solution, and the mixture was stirred at 80°C for several hours until the solution became transparent. This solution, with a molar ratio (Ba + Sr)/Sn/CA/EG = 1/1/10/40, was heated at 130°C to produce a yellowish transparent resin without any precipitation. The pyrolysis of the resin at 350°C yielded a powder precursor for (Ba,Sr)SnO₃. Pure SrSnO₃ is found with a pseudo cubic structure, which has some deviation from the perfect cubic lattice. X-ray diffraction (XRD) indicated the formation of pseudo-cubic (Ba,Sr)SnO₃ when the barium, strontium-tin precursor was heat treated in air at 600°C or above for 2 h. The solid solution of (Ba,Sr)SnO₃ exhibited a transition from the ideal cubic structure to a pseudo cubic structure.