Study of structural order–disorder thermal dependence dielectric properties for PbHPO4 and PbHAsO4 crystals

Abstract

By using the statistical Green function theory and extended two sublattice pseudospin lattice coupled mode model Hamiltonian for proton subsystem with mean field approximation on hydrogen bonds have been used to interpret structural phase transition thermal dependence dielectric properties in PbHPO $$_{4}$$ and PbHAsO $$_{4}$$ ferroelectric compounds. By using the retarded thermal Green function theory and Hamiltonian along with Dyson approach, the expressions for ferroelectric soft mode frequency, dielectric permittivity and dielectric tangent loss have been derived. With the putting of the model values of different physical parameters in theoretical derived expressions, the thermal dependence of ferroelectric normal mode frequency, relative permittivity and dielectric loss has been calculated for both ferroelectric compounds in two structural phases. With the help of proper fitting of model parameters, valuable theoretical results for corresponding experimental results have been calculated.