Phase relations and microwave dielectric properties of vanadium modified Ba_5Nb_4O_(15) ceramics

摘要

Microwave dielectric ceramics of Ba_5Nb_(4-x)V_xO_15) (x = 0-1) were prepared by a solid-state reaction method. Vanadium substitution can markedly lower the sintering temperature of Ba_5Nb_4O_(15) from 1450 to 1100℃. The X-ray powder diffraction analysis reveals the multiphase nature of this system. A hexagonal-to-orthorhombic phase transition was also observed for the BaNb_2O_6 secondary phase. The microwave dielectric properties, such as τ_f, ε_r and Q x f value, decreased with increasing vanadium content for samples sintered at 1100℃. There was an apparent increase in τ_f and Q x f value for samples (x ≥ 0.5) sintered at 1200℃ due to the hexagonal-to-orthorhombic phase transition of the BaNb_2O_6 phase. These results suggested that the microwave dielectric properties of multiphase ceramics strongly depended on the phase compositions and the phase transitions.