Sintering Process and Microwave Dielectric Properties of Bi8TiO14 Ceramics

Abstract

The formation of a homogeneous Bi8TiO14 phase was successfully achieved in a specimen calcined at 600 C. However, a Bi4Ti3O12 secondary phase also developed in specimens calcined at temperatures higher than 600 degrees C, probably because of Bi2O3 evaporation. For specimens sintered above 800 degrees C, a small amount of the Bi8TiO14 phase melted during sintering, with the liquid phase contributing to the densification of the specimens; however, Bi4Ti3O12 and Bi12TiO20 secondary phases were still formed in these specimens. The microwave dielectric properties of the Bi8TiO14 phase were considerably affected by variations in the microstructure of the specimens. When the sintering temperature exceeded 825 degrees C, the amount of secondary phases increased, and this decreased the density and Qxf values of the specimens. Bi8TiO14 ceramics sintered at 825 degrees C exhibited promising microwave dielectric properties, with epsilon(r) = 47.4, Qxf = 5370 GHz, and tau(f) = -16.01 ppm/degrees C.