Microwave Dielectric Properties and Microstructures of Ca_1-<i>x</i>Nd_2<i>x</i>/3TiO₃–Li_1/2Nd_1/2TiO₃Ceramics

Abstract

The microwave dielectric properties and microstructures of (1-y)Ca1-xNd2x/3TiO3–yLi1/2Nd1/2TiO3 ceramics, prepared by a mixed oxide route, have been investigated. A maximum quality factor Q×f=8600 GHz (where f is the resonant frequency) was achieved for samples with y=0 and x=0.39, although the dielectric properties varied with sintering temperature. The Q×f value of (1-y)Ca1-xNd2x/3TiO3–yLi1/2Nd1/2TiO3 increased up to 1400°C, after which it decreased. The decrease in dielectric properties was coincident with the onset of rapid grain growth. In the (1-y)Ca1-xNd2x/3TiO3–yLi1/2Nd1/2TiO3 system, as y increased, the temperature coefficient of resonant frequency (τf) decreased from 800 to 8 ppm/°C for y=0.52 (x=0.39). However, the optimum combination of microwave dielectric properties was achieved at 1400°C for samples where y=0.45 (x=0.39) with a dielectric constant εr of 101, a Q×f value of 5300 (at 7.2 GHz) and a τf value of +13 ppm/°C.