Polarization and dielectric constant of KDP-type crystals

Abstract

The polarization and the dielectric constant of some KDP-type crystals (KH2PO4, K(D1-xH.)2PO4, RbH2PO4, CsH2 AsO4 and KH2AsO4) are measured for various temperatures and poling fields. The form of the function 0, introduced in the phenomenological expression G(T, P) = G0(T) + 1/2A(T - T0)P2 + ø of the free energy, is discussed. The spontaneous polarization is computed from the values of C, and its variations with temperature are compared to the four cluster approximation model.The values of the dielectric constant in the ferroelectric phase, the latent heat of transition and the excess of specific heat deduced from G are shown to agree with experimental data.