Densification, microstructural evolution, and dielectric properties of hexagonal Ba(Ti1−xMnx)O3 ceramics sintered with fluxes

Recently, doped hexagonal BaTiO3 (6h-BaTiO3) ceramics have been reported as potential candidates used in microwave dielectric resonators. However, similar to other common microwave ceramics, doped 6h-BaTiO3 ceramics require a high sintering temperature, greater than 1300 °C. In this study, the effect of sintering aids, including Bi2O3, B2O3, BaSiO3, Li2CO3, CuO, V2O5, 5ZnO·2B2O3, and 5ZnO·2SiO2, on the densification, microstructural evolution, and microwave properties of the 6h-Ba(Ti0.85Mn0.15)O3 ceramics was examined. Results indicate that among the fluxes studied, Bi2O3, B2O3, and Li2CO3 could effectively reduce the sintering temperature of 6h-Ba(Ti0.85Mn0.15)O3 ceramics through liquid phase sintering, while retaining the hexagonal structure and the microwave dielectric properties. The best results were obtained for the 6h-Ba(Ti0.85Mn0.15)O3 with the additions of 5 wt% Bi2O3 sintered at 900 °C (ɛr: 54.7, Qfr: 1323, and τf:183.3 ppm/°C), 10 wt% B2O3 sintered at 1100 °C (ɛr: 54.4, Qfr: 3448, and τf: 254.5 ppm/°C), and 5 wt% Li2CO3 sintered at 950 °C (ɛr: 43.7, Qfr: 2501, and τf: −29.8 ppm/°C).