On the Pressure-Temperature Phase Diagram of Ferroelectric Triglycine Selenate

The pressure-temperature phase diagram of triglycine selenate was studied by measuring the dielectric constant at high pressures. As hydrostatic pressure increases the ferroelectric Curie temperature linearly increases with a coefficient of d T c /d p =(3.45±0.03)×10 -3 deg kg -1 cm 2 which is in good agreement with the value previously reported by Polandov and Jona-Shirane. The transition from the ferroelectric II phase to the pressure induced non-ferroelectric III phase shows progressively large hysteresis during increasing and decreasing pressure-runs at low temperatures. In equilibrium, the non-ferroelectric III phase appears not to be stabilized at atmospheric pressure.