A novel (1−x)MgZrTa2O8–xMgTa2O6 microwave dielectric composite ceramic with near-zero temperature coefficient

In this study, (1−x)MgZrTa2O8–xMgTa2O6 (0.5 ≤ x ≤ 0.8) microwave dielectric ceramics made by solid-state sintering were examined to obtain near-zero resonant frequency temperature coefficient. The effects of MgTa2O6 on the phase transitions, microstructure, and microwave dielectric properties for (1−x)MgZrTa2O8–xMgTa2O6 ceramics were investigated. With the increase of MgTa2O6 content, the composition transformed from single phase MgZrTa2O8 solid solution to MgZrTa2O8 and MgTa2O6 coexistence. As MgTa2O6 ceramic increased, the εr was gradually higher, but the Q×f value kept decreasing. The changes in microwave dielectric properties were explained by the secondary phase, the relative density, Raman shift and FWHM value. Results revealed that the desirable dielectric properties were obtained by sintering at 1450 °C with x = 0.75: εr = 24.88, Q×f= 26,823 GHz, and τf=−0.54 ppm/°C. The highest Q×f (~ 32,518 GHz) was obtained by sintering at 1475 °C with x = 0.5 in the study.