Ultrasonic Studies of Ferroelectric Phase Transition in Gly-H₃PO₃ Crystals

Abstract

The temperature behaviour of the longitudinal and transverse ultrasound wave velocities and attenuation in the region of the ferroelectric phase transition (T c -225 K.) of the glycine phosphite (Gly-H 3 P0 3 ) crystals is studied. The obtained results are considered within the framework of phenomenological theory.

Piezoelectric properties of GPI crystals

“…The elastic properties investigated in the piezoelectric studies revealed, instead of the remarkable jump of the elastic stiffness and compliance at T C expected on the basis of the ultrasonic measurements reported in [9][10][11] and Brillouin scattering experiments [12], a very small anomaly of the elastic stiffness and compliance.…”

“…Information on the order of the phase transition and coupling between the order parameter and elastic properties of the crystal was inferred from ultrasonic studies [9][10][11] and a Brillouin scattering experiment [12]. The experiments revealed a sound velocity jump at T C and the ultrasonic study results [9] indicated a pseudoproper character of the phase transition at T C .…”

Proton Ordering Model of Phase Transitions in Hydrogen Bonded Ferrielectric Type Systems: The Gpi Crystal

“…It is a consequence of a weak coupling due to the layered arrangement along the a-axis and the hydrogen bonding of ionic groups along the c-axis. The observed temperature anomalies of elastic constants in the vicinity of the T c [15] were explained as a manifestation of the probably pseudoproper origin of ferroelectricity in GPI due to anharmonic interaction of the order parameter with deformation of the crystal lattice.…”

Dielectric Dispersion around the Ferroelectric Phase Transition in Partially Deuterated Glycine Phosphite

“…Since the phase transition temperature is shifted to 322 K by deuterium substitution for hydrogen [4,5], ordering of protons in hydrogen bonds expects to be important in the phase transition. The phase transition has been proved to have order-disorder nature from a critical slowing down of the dielectric dispersion of Debye type [4][5][6], hydrostatic pressure effect study [7], ultrasonic study [8][9][10], photopyroelectric study [11], Brillouin scattering [12,13], Raman scattering [4,14], and EPR study [15]. Recently, it is revealed by a series of neutron and X-ray diffraction experiments [16][17][18][19][20] that the hydrogen or deuteron in the bonds are disordered in the paraelectric phase and are ordered in the ferroelectric phase, respectively.…”