Improved giant dielectric properties in microwave flash combustion derived and microwave sintered CaCu3Ti4O12 ceramics

摘要

The nanocrystals of CaCu3Ti4O12 ceramic were prepared by microwave flash combustion technique. The microwave sintering of powders was optimized to 1025 - 1075 degrees C for 20min with heating and cooling rate of 50 degrees C/min. Microstructural evaluation of sintered sample was carried out using SEM. The dielectric properties were measured in the frequency range 10-2x10(6)Hz and the temperature range 30-100 degrees C. The CCTO sample sintered at 1075 degrees C had giant dielectric constant 53,300 at 100Hz. It was observed that dielectric constant was greatly increased on a slight increase in sintering temperature. Modulus and impedance analysis were performed to explore the observed unusual dielectric response. Grain and grain boundary resistance were observed as 8 and 350,000 , respectively. The grain boundary activation energy for electro-conduction was calculated as 0.65eV by using the characteristic frequencies in cole-cole plots. It was noticed that the thermally activated charge carriers had long-range mobility.