Growth of Nanocrystalline CaCu3Ti4O12 Ceramic by the Microwave Flash Combustion Method: Structural and Impedance Spectroscopic Studies

Nanocrystalline CaCu3Ti4O12 ceramic powders of particle size ranging from 50 to 70 nm have been grown for the first time by the microwave flash combustion method. The structural and compositional properties of powders and sintered pellets are analyzed by X-ray diffraction, high-resolution transmission electon microscopy, scanning electron microscopy, and energy dispersive X-ray spectroscopy. The dielectric properties are measured in the frequency range of 10 Hz to 8 MHz at temperatures 20-140 degrees C. Impedance spectroscopic studies reveal that the resistance of the grain and the grain boundary are 40 Omega and 8 M Omega, respectively. It is further observed that on increasing the measurement temperature, the decrease in the grain boundary resistance is relatively higher as compared to grain resistance. Simultaneously, the value tan delta at low frequencies (<2 kHz) increases exponentially with an increase in measurement temperatures (>80 degrees C). These losses are attributed to the thermally activated grain boundary electrical conduction due to copper segregation at the grain boundary. The activation energy for charge conduction is calculated to be 0.776 eV.