Longitudinal field influence on phase transition and physical properties of the KH₂PO₄ family ferroelectrics

Abstract

We verify whether the previously developed model of a KD₂PO₄ crystal, with the shear strain varepsilon₆ taken into account, is able to describe the longitudinal electric field E ₃ influence on the KH₂PO₄ family ferroelectrics. Major effects of the strain varepsilon₆ are splitting of the Slater energies of the short-range correlations and the effective field created by piezoelectric coupling. Calculated T _C-E ₃ phase diagrams, field dependences of polarization, susceptibility, and elastic constant of deuterated KD₂PO₄ and pure KH₂PO₄ well accord with the available experimental data. For a consistent description of all dielectric and piezoelectric characteristics of the crystals, phonon degrees of freedom must be taken into account.

Key Words:

• ferroelectrics
• electric field
• critical point
• shear strain: piezoelectricity