Quantitative estimation of inter-dipole interaction energy in giant-permittivity CaCu3Ti4O12 solid bulks

In the CaCu3TiO4 solid bulks with the giant permittivity of ∼104, the 100-fold permittivity-drop below 200 K has been observed without any long-range structural transition. In the frame of the comprehensive model, the Ising-model analysis of dielectric polarization is applied and the energy of the nearest interaction among the dipoles is deduced from the experiments by utilizing the particle swarm optimization. The interaction energy of ∼56 meV is reasonably smaller than the experimental value of the thermal activation energy of ∼88 meV. The interaction energy is independent of the temperatures, the dipole-chain lengths, and the frequencies of the applied AC electric field. Therefore, such appropriate, stable, and intrinsic interaction energy makes the many-body dielectric relaxation rather than the structural transition responsible for the permittivity drop.