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.
Highlights
Investigations of the pressure and field effects on physical properties of ferroelectrics are urgent because they make it possible to deeper understand the mechanisms of phase transitions in these materials as well as to carry out a search for the new physical effects, which are not observed under zero pressure and zero external field.A ferroelectric with hydrogen bonds CsH2PO4 (CDP) is an example of the crystal where the pressure and field effects are essential
Tc = 153 K, the crystal passes into the ferroelectric phase [3, 4] with spontaneous polarization along crystallographic b-axis, and the protons occupy mainly the upper equilibrium position
In order to describe the smearing of the phase transition, in the present paper we modified the model [15] assuming that the effective dipole moment on a hydrogen bond depends on the order parameter on this bond because the order parameter depends on temperature continuously near the phase transition point
Summary
Investigations of the pressure and field effects on physical properties of ferroelectrics are urgent because they make it possible to deeper understand the mechanisms of phase transitions in these materials as well as to carry out a search for the new physical effects, which are not observed under zero pressure and zero external field. In [15, 16], the effective dipole moments, which have different values in the paraelectric and ferroelectric phases, were used to calculate the longitudinal dielectric permittivity εyy This leads to the appearance of a break on the curve εyy(T) instead of the rounded maximum at the presence of the external field Ey. in order to describe the smearing of the phase transition, in the present paper we modified the model [15] assuming that the effective dipole moment on a hydrogen bond depends on the order parameter on this bond because the order parameter depends on temperature continuously near the phase transition point
Sign-in/Register to view highlights & summary Sign-in/Register to access full text options 
Free) 
Talk to us
Join us for a 30 min session where you can share your feedback and ask us any queries you have
Schedule a call
