Temperature dependence of ferroelectric mode frequency, dielectric constant and loss tangent in potassium dihydrogen phosphate crystal

Abstract

Potassium Dihydrogen Phosphate (KH2PO4, KDP) is an inorganic phosphate which undergoes ferroelectric transition at 123 K. A simple pseudospin lattice coupled mode model with addition of third and fourth-order phonon anharmonic interaction terms, external electric field term and direct spin–spin interaction terms with double-time thermal Green’s function method has been used for derivation of response function. From response function, shift, width, and soft mode frequency have been derived for KDP crystal. Response function is also related to dielectric constant which has been calculated and compared with experimental data of literature value which shows a good agreement.