Anomalous Dielectric Behavior in A-site Ordered Perovskite CaCu3Ti4O12 : Effect of A′-site Doping

The effect of partial replacement of Cu ions by small Be cations with no d-electrons in CaCu3Ti4O12 ceramics was studied over the temperature range from 90 K to 800 K. Dielectric constant of CaCu3(1−x)Be3xTi4O12 decreases exponentially with increasing x as e′ =4000 + exp(-x/0.023); by 5% of Be-doping, the relaxation time and activation energy decrease to values of 50% and 92% compared with those in pure CCTO, respectively. The weakened hybridization in Cu-O bonds by Be-doping suppresses dielectric properties. This evidence indicates that the role of A′-site ions is important for anomalous dielectric response in CaCu3Ti4O12 at high temperatures.