Dielectric properties of microwave flash combustion derived and spark plasma sintered CaCu₃Ti₄O₁₂ ceramic: role of reduction in grain boundary activation energy

Abstract

CaCu₃Ti₄O₁₂ nanocrystals have been synthesized by the microwave flash combustion technique. The calcined powders were spark plasma sintered at 1050 °C for 10 min. The surface morphology of sintered samples was studied by SEM. The effects of grain boundary activation energy on dielectric properties of CCTO were investigated by collecting the dielectric data in the frequencies of 30 Hz–8 MHz at temperatures of 20–100 °C under dc bias of 0–6 V. The potential energy barrier at grain boundary has been examined by dc bias experiments. It is observed that, with an increase in dc bias from 0 to 6 V, the grain boundary activation energy decreases from 0.532 to 0.463 eV. The reduction in such grain boundary activation energy results in the decrease in dielectric constant. It is noticed that CCTO ceramic at room temperature under zero dc bias has a colossal dielectric constant of 20,000 (at 100 Hz). Using the cole–cole plot, grain and grain boundary resistance are calculated to be 13 and 52,100 Ω, respectively.