Intrinsic and extrinsic relaxation of CaCu₃ Ti₄ O₁₂ ceramics: Effect of sintering

The effect of sintering process on the electrical properties of CaCu ₃ Ti₄ O₁₂ (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 V_O⁺⁺, proposed as extrinsic and intrinsic relaxations, are responsible for the dielectric behaviors of CCTO ceramics.