have a common boundary
3.We have developed the theory of boundary shielding approximation of electric polarization,from which the values of spontaneous polarization of some typical ferroelectric materials can be derived.The shielded charges in ferroelectricity are in the state of surface bound polaron-dipole whose creation and annihilation must span a potential barrier.By introducing statistical method,four types of typical electric hysteresis loops of some common crystals and ceramics have been given,which are well consistent with the experimental results.
