Nanocrystalline CaCu3Ti4O12 powder by PVA sol–gel route: synthesis, characterization and its giant dielectric constant

Abstract

Nanocrystalline CaCu3Ti4O12 powders were synthesized by a simple PVA sol–gel route and calcined at 700 and 800°C in air for 8 h. The diameter of the powders ranges from 40–100 nm. The calcined 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 had a typical perovskite CaCu3Ti4O12 structure although the sintered samples contained some amount of CaTiO3. SEM of the sintered CaCu3Ti4O12 ceramics showed the average grain sizes of 13–15 μm. The samples exhibit a giant dielectric constant, e′∼105 at 150 to 200°C with weak temperature dependence below 1 kHz in the sample sintered using the powders calcined at 700°C. The Maxwell–Wagner polarization mechanism is used to explain the high permittivity in these ceramics. It is also found that all sintered samples have the same activation energy of grains, which is ∼0.122 eV.