The reaction sequence and dielectric properties of BaSm2Ti4O12 ceramics

To establish the correct reaction sequence of BaO–Sm2O3–4TiO2, phases present in different calcining temperatures are identified by X-ray diffraction patterns. When different calcining temperatures are used, the source phase BaO (BaCO3) consumes below 850°C, the source phases TiO2 and Sm2O3 consume at 1000 and 1150°C; the intermediate phases BaTiO3, BaTi4O9, and Sm2Ti2O7 consume at 1050, 1200, and 1250°C, respectively. The BaSm2Ti4O12 phase starts to reveal at the 1100°C-calcined powder. The integrating intensity of BaSm2Ti4O12 phase increases with the raising of calcining temperatures, accompanying with the decrease of integrating intensities of the source and intermediate phases. As the sintering temperature increases, the densities, quality values, and dielectric constants of BaSm2Ti4O12 ceramics increase and saturate at 1325oC. The BaSm2Ti4O12 ceramics sintered at 1325°C have the properties of Q∗f=5180,εr=81.8, and τf=−19.2 ppm/°C.