Effect of hydrostatic pressure and longitudinal electric field on phase transitions and thermodynamic characteristics of quasione-dimensional CsH2PO4 ferroelectric

Abstract

We propose a two-sublattice proton ordering model for the quasione-dimensional CsH 2 PO 4 ferroelectric with hydrogen bonds, which takes into account linear on lattice strains u 1 , u 2 , u 3 and u 5 contribution to the energy of proton subsystem. The model also takes into account the dependence of effective dipole moments of pseudospins on the order parameters, which enables one to agree the effective dipole moments in paraelectric and ferroelectric phases. Within this model in two-particle cluster approximation on short-range interactions and in the mean field approximation on long-range interactions, there is investigated the behaviour of spontaneous polarization, longitudinal dielectric permittivity and molar heat capacity under the action of hydrostatic pressure and longitudinal electric field. The phase transition into antiferroelectric phase under high pressures is explained. The character of smearing of the paraelectric-ferroelectric phase transition as well as suppression of the antiferroelectric phase at the presence of electric field is studied.

Effect of hydrostatic pressure on dynamic dielectric characteristics of CsH2PO4 ferroelectric

“…To calculate the dynamic characteristics of CDP, we use the model [25], which considers a system of protons on O-H ... O bonds with two-minimum potential as a system of pseudospins. The primitive cell has one chain, marked in figure 1 as "A".…”

“…The primitive cell has one chain, marked in figure 1 as "A". To describe the transition to antiferroelectric phase at high pressures, paper [25] considers an extended primitive cell formed by two chains ("A" and "B"). All chains "A" form a sublattice "A", and all chains "B" form a sublattice "B".…”

“…Minimizing the thermodynamic potential with respect to the strains, an additional system of equations for the strains 𝑢 𝑗 was obtained in [25]:…”

“…In this paper, based on the model [25], the dynamic dielectric characteristics of CDP in the presence of hydrostatic pressure are calculated.…”

“…In [23][24][25][26], there is proposed a two-sublattice pseudospin model of the deformed crystal CDP, in which the interactions between the nearest pseudospins in the chain are considered in the mean field approximation. In this case, the interaction parameters are linear functions of the strains 𝑢 𝑗 .…”