Detailed Analyses and an Extension of the Slater Theory of the Phase Transition in KH₂PO₄

Abstract

After detailed analyses of the Slater theory of the ferroelectric phase transition in KH₂PO₄, an extension of it has been tried by introducing into it the terms of the second and the fourth orders in an order parameter, i.e., the polarization, each representing the dipole interaction and the electrostriction. By constructing phase diagrams in the space of temperature and newly introduced parameters, the nature of the transition point derived from the Slater theory become more clearly understood, i.e., it is a triple point and at the same time can be regarded as an end point of the tricritical line.