We report an empirically derived formula to describe thermally and electrically excited relaxation processes arising in materials with electrical inhomogeneities. This formula was deduced from the temperature and electric field-dependent conductivity of calcium copper titanate ceramics and can be used to explain the Schottky barrier behavior of the grain boundary regions that control conductivities. It relates conductivity, activation energy for conduction, breakdown strength, and grain size effects, and is believed to have the potential to explain the high permittivity and breakdown mechanism, as well as the highly nonlinear current-voltage characteristics of these materials of this type.