Anomalous Dielectric Behavior in A -site Ordered Perovskite CaCu 3 Ti 4 O 12 : Effect of A ′-site Doping.

The effect of partial replacement of Cu ions by small Be cations with no d-electrons in CaCu3Ti4O12ceramics was studied over the temperature range from 90 K to 800 K. Dielectric constant of CaCu3(1−x)Be3xTi4O12decreases exponentially with increasing x as ε′ =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 ofA′-site ions is important for anomalous dielectric response in CaCu3Ti4O12at high temperatures. [ABSTRACT FROM AUTHOR]