Glycine Phosphite Crystals Research Articles

Characterization of Ferroelectric Phase Transition in Deuterated Glycine Phosphite Crystal

Dielectric, dilatometric, and ultrasonic studies around the ferroelectric phase transition at 319 K were done. Measurement of relative electric permittivity showed the existence of a strong bias field which causes in studied samples some diffused character of phase transition. However, all presented measurement confirmed the continuous character of phase transition. The obtained data are similar to those received earlier in the case of hydrogenated glycine phosphite crystal.

Electric Field Effect on Dielectric Constant of Glycine Phosphite

Study of the effect of an external electric field on the dielectric constant in the paraelectric phase of ferroelectric glycine phosphite crystals has been performed. The dielectric constant behavior under the bias external field has been analyzed in the framework of Landau theory. It is shown that the ferroelectric phase transition is of the first order very close to a tricritical point and the calculated value of the thermal hysteresis is j T ; 0.1 K.

Dielectric Investigation of Glycine Phosphite Crystal

The complementary measurements of the dielectric dispersion in ferroelectric phase of glycine phosphite crystal at the frequency range of 200 Hz -1 MHz have been carried out. The analysis of the dielectric spectra of the low frequency relaxation process showed that it can be fitted by two Debye-type relaxators. The activation energy of the both processes has been calculated. The observed behaviour of the relaxators suggests that they are connected with a domain structure; one with the growth of the nuclei whereas the second with the domain wall movement.

Acoustic and dielectric anomalies in the temperature range of a ferroelectric phase transition in glycine phosphite crystals

The acoustical and dielectric properties of glycine phosphite crystals are investigated in the temperature range of a ferroelectric phase transition. The acoustic anomalies for longitudinal waves along the X, Y, and Z crystallographic axes (where Y is the spontaneous polarization axis) are analyzed in the framework of the Landau theory. It is shown that pronounced acoustic anomalies of the velocity can be quantitatively described within the pseudoproper ferroelectric phase transition model with due regard for the long-range dipole-dipole interaction. For longitudinal acoustic waves propagating along the polar crystal axis, the striction anomaly of the velocity is only partly suppressed by the long-range dipole-dipole forces and an abrupt jump in the velocity is observed in the vicinity of the phase transition. The temperature coefficients of the velocity in the paraphase are determined. The striction contribution and the contributions biquadratic in the order parameter and in the strain to the velocity anomaly are separated.

Preparation of Ferroelectric Glycine Phosphite Single Crystals

An experimental procedure to prepare single crystals of ferroelectric glycine phosphite (GPI) is presented. Since the solubility of GPI in water increases with temperature, the single crystals are grown from fine seed crystals in a saturated aqueous solution by the gradually-decreasing-temperature method. Full faced, transparent, colorless crystals weighing about 10 g are obtained within 20–30 days. Crystallographic axes and the Miller indices for all faces of the obtained crystals are determined using the lattice parameters as a clue.

Twinning in GLY·H3PO3 crystals

Systematic polarized microscopic observation were done for glycine phosphite crystals along the b-axis. In some as grown crystals natural twinning was found in the (001) plane. Occasionally, appearance of twins in single domain crystals was observed during cracking or polishing of the samples and therefore the crystal can be regarded as at least potentially ferroelastic.

Ferroelectricity in partially deuterated glycine phosphite crystals

Crystals of Gly·H3PO3 with various degree of deuteration were grown and their physical properties were investigated. Anomalies of permittivity related to para- ferroelectric phase transition were observed in the whole range of deuterium content. Ferroelectric character of the observed phase transitions was confirmed from hysteresis loops observation and pyroelectric measurement. The dependence of Tc on deuterium content was found to be linear.

Linear birefringence in ferroelectric glycine phosphite and deuterated glycine phosphite

Linear birefringence changes were measured with the rotating analyzer method for the glycine phosphite crystal and its deuterated analogue in the vicinity of ferroelectric phase transition. Continuous character of the phase transition was assured. Power rule was found as fulfilled only in close vicinity of Tc. Evident isotope effect was denoted: deuteration changes Tc from 225 to 324K.

Study of the elastic properties of glycine phosphite crystals (Gly·h3PO3) by Brillouin scattering

The results concerning the elastic properties of glycinium phosphite (GPI) crystals obtained by Brillouin scattering method are reported. The temperature measurements of the relative change AVN of the phase velocity for acoustic modes propagating in q = [100], q = [010], q = [110] and q = [011] directions have been performed in the temperature range 300 K - 170 K. Obtained results confirm the existence of the ferroelectric phase transition (P21/a - P21) at 224 K.

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 (Tc = 225 K) of the glycine phosphite (Gly-H3PO3) crystals is studied. The obtained results are considered within the framework of phenomenological theory.

Dielectric dispersion and vibrational studies of a new ferroelectric, glycinium phosphite crystal

The dielectric dispersion in glycine phosphite crystal over the frequency range 30 - 1000 MHz is presented. Ferroelectric dispersion of the Debye type along the b-axis occurs in the microwave-frequency region and is caused by a single relaxational soft mode. The powder IR (at low temperatures between 300 and 14 K) and FT Raman spectra in the region between 4000 and are measured. DSC measurements for the GPI and deuterated crystals are performed. The results confirm the order - disorder nature of a proper ferroelectric phase transition of second order.