Effect of Microstructure on Microwave Dielectric Properties of Al₂O₃-Added Ba(Zn_1/3Ta_2/3)O₃ Ceramics

Abstract

The effects of Al 2 O 3 additive on the microstructure and microwave dielectric properties of Ba(Zn 1/3 Ta 2/3 )O 3 (BZT) ceramics were investigated. The BZT ceramics has a 1:2 ordered hexagonal structure. The degree of the 1:2 ordering did not decrease with the addition of Al 2 O 3 . Grain growth occurred and the liquid phase formed for the Al 2 O 3 -added BZT ceramics sintered above 1580°C. The liquid phase contains high concentrations of Ba and Al ions, which could be responsible for the grain growth. When a small amount of Al 2 O 3 was added, the relative density slightly decreased but the Q value was markedly enhanced. The increase in the Q value was not related to the relative density or the 1:2 ordering. In contrast, the improvement in the Q value occurred in specimens in which grain growth occurred. Therefore, the increase in the grain size is considered to be responsible for the improvement in the Q value of Al 2 O 3 -added BZT.