Influence of electric field E₃ and mechanical shear stress σ₆ on KH₂PO₄ crystal ferroelectric phase transition

Abstract

Within the theory due to Levitskii and Lisnii (2004), which takes into account short-range and long-range interactions, proton tunnelling, and piezoelectric coupling, we explore the influence of the electric field E ₃ and mechanical shear stress σ₆ (tetragonal crystallographic reference system) on the thermodynamics of the ferroelectric phase transition in KH₂PO₄ crystals. The (E ₃, T _C) and (σ₆, T _C) phase diagrams are calculated with the critical points (11.9 kV m⁻¹, 122.778 K) and (71.3 kPa, 122.778 K), respectively. The obtained dependences of the latent heat on the field and stress are nonlinear. We consider the temperature dependences of polarization and strain u ₆ at different values of the field and stress. The theoretical results are compared with experiment.

Keywords:

• Ferroelectric phase transition;
• Potassium dihydrogen phosphate;
• Electric field;
• Shear stress

Keywords:

• 82B26
• 82B27
• 82D45