Microstructure and microwave dielectric properties of Ba5(Nb1-xTax)4O15 (x=0∼0.5) ceramics

The Ba-5(Nb1-xTax)4O(15) (x=0similar to0.5) solid-solution ceramics with hexagonal perovskite structure were prepared by solid-state oxide route. The phases and structure of the sintered ceramics were characterized by X-ray diffraction (XRD) and scanning electron microscopy (SEM). The influences of composition and sintering temperature on the bulk density, microstructure and microwave dielectric properties were also investigated. As the value of x increased from 0 to 0.5, the Qxf value increases from 36,049 to 49,493 GHz (at similar to9GHz), whereas the dielectric constant (epsilon(r)) decreases from 39.21 to 33.03 and the temperature coefficient of resonant frequency (tau(f)) decreases from 78.6 to 19.4 ppm/degreesC. The results indicate that the microwave dielectric properties of Ba-5(Nb1-xTax)(4)O-15 ceramics can be easily modified in a large range by changing the relative content of Ta to Nb.