Effects of microstructure on the microwave dielectric properties of Ba(Co1/3Nb2/3)O3 and (1-x)Ba(Co1/3Nb2/3)O3-xBa(Zn1/3Nb2/3)O3 ceramics

Ba(Co1/3Nb2/3)O-3(BCN) has a 1:2 ordered hexagonal structure. A large amount of the liquid phase, which contains high concentrations of Ba and Nb ions was found in the BCN ceramics. Q-values of BCN increased with increasing sintering temperature; however, it significantly decreased when the sintering temperature exceeded 1400 degreesC. The presence of a large amount of liquid phase could be responsible for the decrease of the Q-value. For (1-x)Ba(Co1/3Nb2/3)O-3-xBa(Zn1/3Nb2/3)O-3 [(1-x)BCN-xBZN] ceramics, the 1:2 ordered hexagonal structure was observed in the specimens with xless than or equal to0.3 and the BaNb6O16 second phase was found in the specimens with xgreater than or equal to0.6. Grain growth, which is related to the BaNb6O16 Second phase occurred in the specimens with xgreater than or equal to0.5. In this work, the excellent microwave dielectric properties of tau(f)=0.0 ppm/degreesC, epsilon(r)=34.5 and Qxf=97,000 GHz were obtained for the 0.7BCN-0.3BZN ceramics sintered at 1400 degreesC for 20 h. (C) 2003 Elsevier Ltd. All rights reserved.