Maxwell–Wagner relaxation in the CaMn7O12 perovskite

In this work we have measured the complex dielectric permittivity of a polycrystalline material using samples of different thickness (frequency range 20–1 MHz). The results reveal that the CaMn7O12 material is electrically heterogeneous as it consists of regions of different conductivities.In this kind of electrically heterogeneous materials the variation of the dielectric permittivity as a function of temperature can be fitted to a Maxwell–Wagner model. In the case of the CaMn7O12 sample this model fits only partially the experimental data and we need to include three regions of different conductivities to explain the obtained dielectric response.