Synthesis and giant dielectric behavior of CaCu₃Ti₄O₁₂ ceramics prepared by polymerized complex method

Nano-sized powders of CaCu₃Ti₄O₁₂ were synthesized by a polymerized complex method and calcined at 600, 700 and 800 °C in air for 8 h. The diameter of the powders ranges from 30 to 100 nm. The CaCu₃Ti₄O₁₂ powders were characterized by TG-DTA, 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 with some amount of CaTiO₃ and CuO. SEM micrographs of the sintered CaCu₃Ti₄O₁₂ ceramics showed the average grain size of 10-15 μm. The samples exhibit a giant dielectric constant, ε′ of 10,000-20,000. It is found that ε is independent on the frequency and weakly dependent on temperature. The Maxwell-Wagner polarization mechanism is used to explain the high permittivity in these ceramics. It is also found that all three sintered samples have the same activation energy of grains, which is 0.116 eV. On the other hand, the activation energy of grain boundaries is found to be 0.219, 0.391 and 0.641 eV for CaCu₃Ti₄O₁₂ ceramics prepared using the CaCu₃Ti₄O₁₂ powders calcined at 600, 700 and 800 °C, respectively.