Hydrostatic Pressure Effect on Phase Transition in Novel Crystalline 2-Aminopirydyne Phosphate Ferroelectrics

Abstract

Aminopyridine phosphate NC₄H₄NH₂*H₃PO₄ (APP) is a new hydrogen-bonded ferroelectric crystal. One expects that the phase transition at 103.5 K is connected with proton ordering in hydrogen bonds. We have studied the hydrostatic pressure effect on dielectric properties to confirm the role of proton ordering in the molecular mechanism of phase transition in APP crystals. The negative nonlinear shift of phase transition was observed with dT_c/dp\_p=0 = 1.84 K/Gpa. The phase diagram in the pressure–temperature plane is proposed.

Keywords:

• Ferroelectrics
• hydrogen bond
• hydrostatic pressure
• phase transition