Giant Dielectric Properties of CCTO Ceramics Synthesized by Solid State Reaction Route

Abstract

Complex cubic perovskite oxide materials have drawn a lot of interest because of their intriguing physical properties. Notably, their anomalous dielectric properties demand its potential applications in electronic devices such as multilayer capacitors, memory, and varistors. In particular, dielectric permittivity of calcium copper titanate (CaCu3Ti4O12, CCTO) provides a vast potential application in miniaturizing electronic devices. CCTO powder was synthesized by solid-state reaction route by taking CaCO3, TiO2, and CuO precursors. This study is focused on phase formation and dielectric properties of pure CCTO ceramics. 1050°C was optimized as the calcination temperature of CCTO system. To vary the grain size and grain boundaries, CCTO green compacts were sintered at two different sintering temperatures. By using Archimede’s formula, experimental density (dexp) of the sintered samples was calculated. Various characterization techniques were used to study structural, microstructural, dielectric, and vibrational properties. X-ray diffraction (XRD) results confirmed the formation of cubic structured phase pure CCTO. The phase formation is further well corroborated by the Raman and FTIR spectroscopy. Scanning electron microscope reveals the average grain size. The grain size and grain boundaries played the important role for the enhancement of dielectric constant. Importantly, a giant dielectric value in the order of ~105 with low loss at 100 Hz frequency was obtained for CCTO system sintered. The obtained high dielectric value is understood by invoking the internal barrier capacitance effect.