Complex Permittivity of Calcium Copper Titanate Ceramics with a Bimodal Grain Size Distribution

Abstract

The giant dielectric constant of calcium copper titanate (CCTO) has attracted a lot of interests in the last few years. Its dielectric properties, however, appeared to be very sensitive to the processing conditions. In our recent experiments on the processing of CCTOs, we observed the frequent occurrence of microstructure with a bimodal grain size distribution and a correlation between dielectric constant and the percentage of large grains in bimodal CCTOs. In this study, we assumed that CCTO ceramics are barrier layer capacitors and proposed an analytical model to describe the dielectric behavior of CCTOs with a bimodal grain size distribution. More importantly, both the insulating layer and the conductive core were included in the model to describe the complex permittivity and hence relaxation in bimodal CCTOs.