Transport and dielectric measurements have been performed in $\mathrm{Ca}{\mathrm{Cu}}_3{\mathrm{Ti}}_4{\mathrm{O}}_{12}$ ceramics. The bulk ac conductivity shows a power-law behavior at different temperatures, which is related to polaron relaxation. The temperature dependence of the bulk dc conductivity indicates a variable-range-hopping mechanism. The dielectric relaxation frequency deviates from the Arrhenius behavior. An equivalent circuit is used to explain qualitatively the experimental data of $\mathrm{Ca}{\mathrm{Cu}}_3{\mathrm{Ti}}_4{\mathrm{O}}_{12}$.

• Received 2 October 2003

DOI:https://doi.org/10.1103/PhysRevB.70.174306