In heterogeneous dielectric materials such as CCTO ceramics we can see phases with dierent electrical conductivities. The application of an electrical eld to a sample causes the displacement of charge from the phases that are more conductive to those that are less. Especially in low frequency range a space charge and an interfacial polarization e ects associated with it occur. This polarization results in the high values of ε0(ν) and dielectric losses ε00(ν).