Pyridinium salt investigations under high pressure: pressure-induced phase transitions in ferroelectric pyridinium perrhenate

Abstract

The properties of pyridinium perrhenate have been studied by three methods: dielectric spectroscopy, neutron powder diffractometry and NMR spectrometry under high pressure. It has been shown that under high pressure the temperatures of the two phase transitions in the crystal are shifted towards lower ones. Moreover, the results have shown the occurrence of a new high pressure phase with a triple point corresponding to the pressure of 100 MPa and the temperature of 240 K.

Structural phase transitions in pyridinium perrhenate at high pressure

“…The NMR studies of the P-T phase diagram of pyridinium perrhenate PyHReO 4 at pressures up to 0.8 GPa, along with the studies of the electric properties of this compound [5], showed that, at temperatures T < 250 K, there exists a phase transition from ferroelectric phase II to a low-temperature paraelectric phase (phase III).…”

Structural phase transitions and Raman spectra of pyridinium perrhenate at high pressures

“…At P = 2 GPa the phase I is stable in the temperature range 10-293 K, indicating a suppression of the ferroelectricity in C 5 D 5 NHReO 4 by application of high pressure. In addition, an existence of intermediate phase II' with unknown structure at P > 80 MPa was found by dielectric and NMR measurements [7].…”

Dynamics in molecular and molecular-ionic crystals: A combined experimental and molecular simulation study of reorientational motions in benzene, pyridinium iodide, and pyridinium nitrate

“…Much effort has been made to prove that the pyridinium cation really reorients in a temperature dependent asymmetric potential, as such potential allows describing the ferroelectric properties of these compounds. Thus, the compounds pyridinium iodide, 2, 14-16 pyridinium tetrafluoroborate, 17 pyridinium perchlorate, 18,19 pyridinium periodate, [20][21][22] pyridinium perherate, 23,24 and pyridinium nitrate 4 have been studied by 1 H nuclear magnetic resonance (NMR) and inelastic neutron scattering as a function of temperature and pressure and by 2 H NMR and quasielastic neutron scattering (QENS) as a function of temperature. A detailed analysis of the dynamics of molecules or ions provides important information to understand their properties or the mechanism of their phase transitions.…”