Change from second order to first order ferroelectric phase transition by polarization induced strain

The mean field model by Pierre Weiss originally developed for the description of ferromagnetic phase transitions can be applied also to ferroelectric materials. Essentially the model describes a positive feedback effect for the polarization, i. e. the coupling between the dipoles enhances the polarization. However, in its original form the Weiss model yields only a phase transition of the second order for the spontaneous polarization. If strain induced by the polarization itself is considered the second order phase transition can be changed into a first order phase transition.