Liquid phase sintering and microwave dielectric properties of Ba(Mg_1/3Ta_2/3)O₃ ceramics

The effect of CuO addition on the microstructures and the microwave dielectric properties of barium magnesium tantalate Ba(Mg_1/3Ta_2/3)O₃ ceramics has been investigated. It is found that low level-doping of CuO (up to 1 wt%) can significantly improve the density of the specimens and their microwave dielectric properties. The density of doped Ba(Mg_1/3Ta_2/3)O₃ ceramics can be increased beyond 96% of its theoretical density by at sintering 1440°C due to the liquid phase effect of CuO addition observed by scanning electron microscopy. The second phase was not observed for ceramics with 0.25 to 1 wt% CuO additions. The dielectric constant (ε_r) and temperature coefficient of resonant frequency (τ_f) were not significantly affected, while the nonloaded quality factors Q were effectively promoted by CuO addition. The ε_r value of 24.2, Q × f value of 173000 (at 10 GHz) and τ_f value of 1.5 ppm/°C were obtained for Ba(Mg_1/3Ta_2/3)O₃ ceramics with 0.5 wt% CuO addition sintered at 1470°C for 4 h.