Nanocrystalline CaCu3Ti4O12 powders prepared by egg white solution route: synthesis, characterization and its giant dielectric properties

Abstract

Nanocrystalline CaCu3Ti4O12 powders with particle sizes of 50–90 nm were synthesized by a simple method using Ca(NO3)2·4H2O, Cu(NO3)2·4H2O, titanium(diisoproproxide) bis(2,4-pentanedionate) and freshly extracted egg white (ovalbumin) in aqueous medium. The synthesized precursor was characterized by TG-DTA to determine the thermal decomposition and crystallization temperature which was found to be at above 400 °C. The precursor was calcined at 700 and 800 °C in air for 8 h to obtain nanocrystalline powders of CaCu3Ti4O12. The calcined CaCu3Ti4O12 powders were characterized by XRD, FTIR, SEM and TEM. Sintering of the powders was conducted in air at 1100 °C for 16 h. The XRD results indicated that all sintered samples have a typical perovskite CaCu3Ti4O12 structure and a small amount of CuO, although the sintered sample of the 700 °C calcined powders contained some amount of CaTiO3. SEM micrographs showed the average grain sizes of 12.0±7.8 and 15.5±8.9 μm for the sintered CaCu3Ti4O12 ceramics prepared using the CaCu3Ti4O12 powders calcined at 700 and 800 °C, respectively. The sintered samples exhibit a giant dielectric constant, e′ of ∼ 1.5–5×104. The dielectric behavior of both samples exhibits Debye-like relaxation, and can be explained based on a Maxwell–Wagner model.