Microwave dielectric properties of gallium-doped hexagonal barium titanate ceramics

High-permittivity and low-loss ceramics with composition BaTi0.92Ga0.08O2.96 have been prepared in the BaO-Ga2O3TiO2 system using the mixed-oxide route. This compound forms as the hexagonal polymorph (6H) of BaTiO3 with the space group P6(3)/mmc. The dielectric properties of dense ceramics have been studied, at microwave frequencies, with the ceramics fired at 1450degreesC under flowing oxygen gas; the results are a relative permittivity, epsilon(r), of similar to74 and a quality factor, Q(.)f(r), of similar to7815 at 5.5 GHz. The quality factor is strongly influenced by the sintering conditions (temperature and atmosphere), whereas the relative permittivity is not influenced significantly by ceramic processing for pellets greater than or equal to93% of the theoretical X-ray density. To our knowledge, this is the first report of microwave dielectric resonance in a perovskite-type BaTiO3-based ceramic.