Phase transition thermal dependence of ferroelectric and dielectric properties in H-bonded $$\hbox {PbHPO}_{4}$$ (LHP) crystal

Abstract

In this paper, the ferroelectric phase transition and dielectric properties in order-disorder type $$\hbox {PbHPO}_{4}$$ crystal are theoretically investigated. We consider the two sublattice pseudospin lattice coupled mode (PLCM) model Hamiltonian modified by adding third and fourth-order phonon anharmonic interactions, indirect coupling interactions, direct spin–spin coupling interaction, and an applied electric field term within mean-field approximation (MFA). The model is developed as a generalization of the semi-microscopic Mitsui mode model. By using the Green’s function theory, two sublattice PLCM model Hamiltonian and Dyson’s equation, the expressions of soft mode frequency, dielectric constant and loss tangent have been derived for $$\hbox {PbHPO}_{4}$$ crystal. The numerical analysis has been performed by fitting the various model parameters in the obtained expressions and the thermal variations of the soft mode frequency, dielectric constant and loss tangent have been obtained. Our theoretical results are compare good with the experimental data of Negran et al. for lead monohydrogen phosphate (LHP) crystal.