Temperature dependent structural Phase transition in Lead Mono Hydrogen Aresenate crystal

A.K Rawat,A Rawat,T.C Upadhyay

doi:10.4038/sljp.v17i0.8028

Abstract

With the use of the modified pseudospin lattice coupled-mode (PLCM) model by adding third-order and fourth-order phonon anharmonic interactions terms and the statistical Green’s function technique a phenomenological explanation of phase transition of the lead monohydrogen arsenate (PbHAsO 4 ) crystal has been given. Expressions for shift, width, dielectric constant, loss tangent and modified ferroelectric soft mode frequency have been derived theoretically. By fitting model values of various quantities obtained from literature in these derived expressions, their temperature dependence has been evaluated numerically. Present theoretically results agree well with the experimental results of others.

Highlights

Due to promising applications in the field of electronics and technology ferroelectric crystals are continuously being attracted to both scientists and physicists
With modified pseudospin lattice coupled-mode (PLCM) model, by adding third-and fourth-order phonon anharmonic interactions terms and double time temperature dependent Green’s function method[12], expressions for shift, width, loss tangent, dielectric constant and modified soft mode frequency have been derived for PbHAsO4 crystal
The loss of power which is known as loss factor in ferroelectrics due to orientation of dipoles is expressed as loss tangent: tan

Summary

INTRODUCTION

Due to promising applications in the field of electronics and technology ferroelectric crystals are continuously being attracted to both scientists and physicists. Lead mono hydrogen arsenate (PbHAsO4) belongs to lead hydrogen phosphate (PbHPO4) type ferroelectric crystals which are called monetites In these crystals the direction of the spontaneous polarization is almost parallel to the direction of H- bond O-H...O projecting on the (010) bonds in the form of one dimensional chain along c-axis. Two sublattice PLCM model with fourth-order phonon anharmonic term was used by Chaudhuri et al.[11] in their calculation These authors have made decoupling of correlations in early stage, as a result of which some important interactions disappeared in their theoretical derived results. With modified PLCM model, by adding third-and fourth-order phonon anharmonic interactions terms and double time temperature dependent Green’s function method[12], expressions for shift, width, loss tangent, dielectric constant and modified soft mode frequency have been derived for PbHAsO4 crystal.

Model Hamiltonian and Green’s function

Green’s functions method

NUMERICAL CALCULATION AND DISCUSSION

CONCLUSIONS