Giant dielectric behavior observed in Ca3Co4O9 ceramic

Giant dielectric properties of a Ca3Co4O9 ceramic, a p-type thermoelectric material, are reported for the first time. A very high dielectric permittivity of about 1.38 × 104 was observed at a temperature of 20°C and frequency of 1 kHz. A Debye-like relaxation behavior with a thermally activated mechanism was observed. The relaxation activation energy was 0.363 eV. It was found that aging time and thermal annealing of the ceramics with Au electrodes have remarkable influence on the value of the dielectric permittivity of this ceramic. Using combined -Z″ and M″ plots, it was found that the giant dielectric response observed in the Ca3Co4O9 ceramic is attributable to the sample-electrode contact effect.