Phase transformation and microwave dielectric properties of BiPO4 ceramics

Abstract

Monazite-type compounds, BiPO4 polymorphs were prepared by the solid-state reaction method. The phase transformation and microwave dielectric properties of sintered ceramics were investigated using the X-ray powder diffraction (XRD) and a network analyzer, respectively. The low-temperature phase of BiPO4 has monoclinic structure, and was transformed into the high-temperature phase with a slight distortion of monoclinic when it is heated above 600 degrees C. The effect of the transformation on the microwave dielectric properties was examined. It was found that the dielectric properties of each phase were significantly different. In particular, the high-temperature phase sintered at 950 degrees C has good microwave dielectric properties; the relative dielectric constant (epsilon(r) ) = 22, the quality factor (Qxf) = 32,500 GHz and the temperature coefficient of resonant frequency (tau(f) ) = -79 ppm/degrees C.