Intrinsic and extrinsic relaxation of CaCu3Ti4O12 ceramics: Effect of sintering.

The effect of sintering process on the electrical properties of CaCu3Ti4O12 (CCTO) ceramic dielectrics were investigated in this paper. It was found that grain size is affected by sintering and the nonlinear current-voltage (I-V) property will decrease with the increased sintering time. Also, the frequency and temperature dependences of dielectric permittivity and loss in the ranges of 10-1-107 Hz and 130-270 K were studied. Two relaxation processes with activation energy of 0.51 eV and 0.10 eV, respectively, were found in the frequency dependence of tan δ and Cole-Cole planes, which can be interpreted in terms of insulating grain boundaries and semiconducting grains. It was suggested that grain boundary Maxwell-Wagner relaxation and ionization of oxygen vacancy VO++, proposed as extrinsic and intrinsic relaxations, are responsible for the dielectric behaviors of CCTO ceramics. [ABSTRACT FROM AUTHOR]