Effect of Ta₂O₅ on microstructure and microwave dielectric properties of Ba(Zn_1/3Ta_2/3)O₃ ceramics

When Ta₂O₅ was added to Ba(Zn_1/3Ta _2/3)O₃ (BZT) ceramics, the degree of the 1:2 ordering increased and the Ba₃Ta₅O₁₅ second phase was formed. Grain growth and liquid phase were also found in Ta₂O ₅ added BZT ceramics sintered above 1580°C. The liquid phase, which is responsible for grain growth, is related to the Ba₃Ta ₅O₁₅ second phase. The Q-value of BZT ceramics sintered above 1580°C was considerably increased with the addition of a small amount of Ta₂O₅. Since the relative density decreased with the addition of Ta₂O₅, the increase of the Q-value is not related to the relative density. In contrast, the improvement of the Q-value could be explained by the increase in the grain size because the average grain size increased with the addition of Ta₂O₅. When a large amount of Ta₂O₅ was added, however, the Q-value became very low even though the grain size was very large. The low Q-value might be attributed to the low relative density and the presence of a large amount of the Ba₃Ta₅O₁₅ second phase.