Effects of surface microstructure on microwave dielectric properties of ZrO₂-NiO added Ba(Zn_1/3Ta_2/3)O₃ ceramics

High frequency dielectric ceramics have potential for applications in mobile and satellite communications systems at frequencies higher than 10 GHz. The Ba(Zn_1/3Ta_2/3)O₃ ceramics are known to have a high quality factor, a small temperature coefficient of the resonance frequency and a high dielectric constant. On the other hands, sintering at high temperature for extended time is required to obtain the ordered structure for high quality factor. In this study, the microwave dielectric properties of ZrO₂ and NiO-added Ba(Zn_1/3Ta_2/3)O₃ ceramics prepared by solid-state reaction have been investigated. Adding ZrO₂ and NiO could effectively promote the densification even the case of decreasing the sintering time. At the surface of samples, secondary phase of Ba-Ta compounds was formed possibly due to the evaporation of ZnO, however, the interior of the samples remained as pure Ba(Zn_1/3Ta _2/3)O₃. The samples sintered at 1600°C for 2 h exhibited 1:2 ordering of Zn and Ta cations. Excellent microwave dielectric properties of Q·f(>96,000 GHz) and ε_r=30 has been obtained.