Densification, microstructural evolution and microwave dielectric properties of fluxed sintered 12R-Ba(Ti0.5Mn0.5)O3 ceramics

Doped hexagonal BaTiO3 (h-BaTiO3) ceramics have recently been identified as potential candidates for use in microwave dielectric resonators. However, similar to other common microwave ceramics, doped h-BaTiO3 ceramics require a sintering temperature higher than 1400 °C. In this study, the effects of Bi2O3 and Li2CO3 on the densification, microstructural evolution and microwave properties of hexagonal 12R-Ba(Ti0.5Mn0.5)O3 ceramics were examined. Results indicate that Bi2O3 and Li2CO3 are able to effectively reduce the sintering temperature of 12R-Ba(Ti05Mn0.5)O3 ceramics through liquid phase sintering while retaining the hexagonal structure and the microwave dielectric properties. The best results were obtained for the 12R-Ba(Ti0.5Mn0.5)O3 with the additions of 5 wt% Bi2O3 sintered at 1200 °C (ɛr: 36.0, Qfr: 6779 GHz, and τf: 25.3 ppm/°C), and 5 wt% Li2CO3 sintered at 1200 °C (ɛr: 28.1, Qfr: 5304 GHz, and τf: 35.3 ppm/°C).