Optimized sintering properties and temperature stability of MgZrTa₂O₈ ceramics with CuO addition for microwave application

Microwave dielectric ceramics CuO–modified MgZrTa₂O₈ were synthesized by the conventional solid-state reaction method. The effects of CuO additives on the sintering characteristics and microwave dielectric properties have been investigated. With CuO addition, the sintering temperature of MgZrTa₂O₈ ceramics can be effectively lowered from 1475 to 1375 °C without decreasing its dielectric properties obviously and the temperature coefficient of the resonant frequency of MgZrTa₂O₈ ceramics have been optimized to near-zero. The crystalline phase exhibited a wolframite crystal structure and no second phase was detected at low addition levels. The grain growth of CuO–modified MgZrTa₂O₈ ceramics was accelerated due to liquid phase effect. The relative dielectric constants (ε_r) were correlated with apparent density and were not significantly different for all levels of CuO concentration. The quality factors (Q × ƒ) and temperature coefficient of resonant frequency (τ_ƒ), which were strongly dependent on the CuO concentration, were analyzed by the grain size and the dielectric constant respectively. A best Q × ƒ value of 116400 GHz and τ_ƒ value of −6.19 ppm/℃ were obtained for specimen with 0.05 wt% CuO addition at 1375 °C.