Study of ferroelectric phase transition and dielectric properties of one dimensional hydrogen bonded crystals

114-119The third- and fourth-order phonon anharmonic interaction terms and spin-lattice interactions have been considered in the two-sublattice pseudospin-lattice coupled mode model for explaining ferroelectric transition and dielectric properties of lead hydrogen arsenate(a one-dimensional hydrogen bonded ferroelectric). Using double time thermal Green’s function technique, expressions for shift and width in frequency, soft mode frequency, dielectric constant and loss tangent have been derived for this crystal. By fitting numeric values of various physical parameters in these expressions, thermal dependences of soft mode frequency, dielectric constant and loss tangent have been calculated. Theoretically obtained thermal variations for dielectric constant has been compared with experimental data of other researchers and with experimentally correlated results for soft mode frequency, which show a good agreement