The influence of the segregation of Cu-rich phase on the microstructural and impedance characteristics of $CaCu_3Ti_4O_{12}$ ceramics

Abstract

The influence of sintering conditions on the microstructural features and impedance characteristics of the giant dielectric constant material $CaCu_3Ti_4O_{12}$ (CCTO) was investigated. The microstructure and impedance characteristics were found to be strongly dependent on the sintering conditions. Sintering of the CCTO ceramics at elevated temperatures $(>1100^ oC)$ for prolonged durations resulted in the segregation of Cu-rich phase, mostly confined to the surface, which was in concomitance with the appearance of the additional semicircle at the low frequency end in Impedance $(Z^\ast)$ plots. The absence of this additional semicircle in the Cu-deficient CCTO ceramics and the appearance of the same in Cu-rich CCTO ceramics that were deliberately fabricated corroborated the above observations. Also, $La_{2/3}Cu_3Ti_4O_{12}$ (LCTO), a low dielectric constant member of CCTO family, which consisted of small grains without the segregation of Cu-rich phase at the grain boundary, did not reveal the presence of additional semicircle in the $Z^\ast$ plots