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

Nanocrystalline CaCu₃Ti₄O₁₂ powders with particle sizes of 50-90 nm were synthesized by a simple method using Ca(NO ₃)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 CaCu₃Ti₄O ₁₂. 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 CaCu₃Ti₄O ₁₂ 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 CaCu₃Ti₄O ₁₂ ceramics prepared using the CaCu₃Ti₄O ₁₂ powders calcined at 700 and 800 °C, respectively. The sintered samples exhibit a giant dielectric constant, ε′ 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.