Barrier Layers Formation in Tin Substituted Calcium Copper Titanate CaCu₃Ti_4−xSn_xO₁₂ (0≤x≤1.0)

Abstract

A few compositions in the system CaCu₃Ti_4−xSn_xO₃ (0≤x≤1.0) were synthesized by solid state diffusion controlled thermochemical process. Powder X-ray diffraction patterns of all the compositions show that these compositions are single phase solid solution. All the samples have cubic crystal structure similar to undoped CaCu₃Ti₄O₁₂. Microstructure shows that average grain size is about 10 μm. Dielectric measurements have been carried out in the temperature and frequency range 300–450 K and 1 kHz–1 MHz, respectively. It has been shown by complex plane impedance and modulus analysis that barrier layers form at grain boundaries in these materials. These barriers impart high value of dielectric constant to the resultant ceramic. Dielectric constant, ε_r can be enhanced and dielectric loss (loss tangent), D can be reduced further by chemical infiltration.