The relationship between microstructure and quality factor for (Al,Mg,Ta)O2 microwave dielectrics

The relationship between microstructures and quality factor (Q) of (1−x)(Al1/2Ta1/2)O2–x(Mg1/3Ta2/3)O2 ceramics was investigated. The extrinsic loss of microwave dielectrics depended on cations ordering, grain size, and porosity. (Al1/2Ta1/2)O2 has a disordered structure and (Mg1/3Ta2/3)O2 has an ordered trirutile structure. As (Mg1/3Ta2/3)O2 content increased, (1−x)(Al1/2Ta1/2)O2–x(Mg1/3Ta2/3)O2 ceramics revealed an ordered phase and were of single phase for x>0.6. The increase of the ordered phase and grain size enhanced the Q. When ordering was completed at (Mg1/3Ta2/3)O2 concentration over 60 mol%, the grain size was a major factor in the increase the Q value. In contrast the porosity degraded the Q value. Therefore, the Q value depended on order/disorder, the porosity, and the grain size in that order.