Therefore, the frequency dependence of the coercive field depends on the ferroelectric itself and the electrode material. In SrBi2Ta2O9 with Pt electrodes the exponential factor s of the empirical relation EC ∝ f −β [32] is about 0.1 in a raw approximation, while in PbZr0.3Ti0.7O3 with Pt electrodes it is about an order of magnitude less.