The effect of sintering temperature on microstructure and microwave dielectric properties of 0.88Ba([Zn0.6Co0.4]1/3,Nb2/3)O3- 0.1Ba(Ga1/2Ta1/2)O3- 0.02BaZrO3 ceramics

Microwave dielectric ceramics are extensively used in systems utilized at microwave frequencies for example mobile telephone and satellite devices. In this study ceramics with 0. 88Ba ([Zn0. 6Co0. 4] 1/3،Nb2/3) O3–0. 1Ba (Ga1/2Ta1/2) O3–0. 02BaZrO3 composition were prepared through the conventional ceramic processing; i. e. mixing and milling of the starting powders، calcination at 1100°C، second milling and sintering of pressed samples at different temperatures. The study showed that increasing sintering temperature resulted in an increase in density so that the highest density was observed at 1500°C. There was also an increase in quality factor (Q´f) when sintering temperature was increased; Q´f was about 16،000 GHz at 1500°C. The increase in quality factor is mainly due to the increase in density. Since superlattice reflections were not observed in XRD spectrum، the increase in quality factor can not be related to an increase in ordering degree. The presence of ordering can also be evaluated by changes in c/a ratio (c and a are lattice parameters of the hexagonal superlattice structure) and changes in lattice distortion. None of these two methods were able to show the existence of ordering.