Microwave dielectric properties and microstructures of Ca_1-xNd_2x/3TiO₃-Li_1/2Nd_1/2 TiO₃ ceramics

The microwave dielectric properties and microstructures of (1 - y)Ca_1-xNd_2x/3TiO_3-yLi_1/2Nd_1/2 TiO₃ ceramics, prepared by a mixed oxide route, have been investigated. A maximum quality factor Q × f = 8600GHz (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)Ca_1-xNd_2x/3TiO_3-yLi_1/2Nd_1/2 TiO₃ 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)Ca_1-xNd_2x/3TiO_3-yLi_1/2Nd_1/2 TiO₃ system, as y increased, the temperature coefficient of resonant frequency (τ_f) 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 ε_r of 101, a Q × f value of 5300 (at 7.2 GHz) and a τ_f value of +13ppm/°C.