Deuterated Glycine Phosphite Research Articles

Dynamical Property of Domain Walls of Deuterated Glycine Phosphite in The Vicinity of Phase Transition

The behaviour of domains of deuterated glycine phosphite (DGPI) was studied in the vicinity of phase transition by direct observation of domain configurations. The field – dependent domain structure has been studied by means of nematic liquid crystal (NLC) method. We present experimental results showing that the disorder in DGPI may influence the dynamics and distribution of the domain walls and dielectric properties in the vicinity of TC. Because of local inhomogeneities in the studied crystal there is the distribution of transition temperatures in the local regions of DGPI crystal.

Ferroelectric films of deuterated glycine phosphite grown in a nitrogen atmosphere

Thin ferroelectric films of deuterated glycine phosphite are grown by evaporation in a nitrogen atmosphere on NdGaO3 and α-Al2O3 substrates. The strong- and small-signal dielectric response of the resulting structures is studied using an interdigitated electrode system predeposited on the substrate. Crystallization of the films in a nitrogen atmosphere makes it possible to significantly (up to 291 K) increase the temperature of the occurrence of dielectric hysteresis loops, which characterize the transition of the film in the ferroelectric state. Unlike films grown in a normal atmosphere, the small-signal dielectric anomaly is heavily smeared with respect to temperature, which is attributed to an inhomogeneous distribution of deuterium over the film.

Ferroelectric films of deuterated glycine phosphite: Structure and dielectric properties

Polycrystalline textured films of deuterated glycine phosphite consisting of single-crystal blocks with lateral dimensions ∼(50–100) μm and a thickness d ∼ (1–5) μm have been grown by evaporation on NdGaO3(100) and α-Al2O3 substrates with preliminarily deposited interdigitated electrodes, as well as on Al substrates. The c* (Z) crystallographic axis in the blocks is normal to the film plane, and the a (X) axis and the polar axis b (Y) are oriented in the film plane. The temperature dependences of the capacitance of the structures measured with the interdigitated electrode system reveal a strong dielectric anomaly at the film transition to the ferroelectric state. The phase transition temperature T c depends on the degree of deuteration D of the glycine phosphite. The maximum value T c = 275 K obtained in the structures studied corresponds to a degree of deuteration of the glycine phosphite D ∼ 50%. The frequency behavior of the dielectric hysteresis loops in glycine phosphite films differs radically from that of the previously studied films of deuterated betaine phosphite, which evidences that polarization switching in these structures proceeds by different mechanisms. It has been that application of a dc bias to the electrodes changes the shape of the dielectric hysteresis loops and shifts them along the electric field axis. The shift of the loops depends on the sign, magnitude, and time of application of the bias. Possible mechanisms underlying the induced unipolarity are discussed.

Temperature dependence of polarization switching in deuterated glycine phosphite single crystals

The influence of temperature on domain switching behaviour has been investigated in deuterated glycine phosphite (DGPI) single crystals. The experimental data have been collected from direct microscopic observation of the domain structure during switching and D–E hysteresis loop registration. In order to clarify the relationship between macroscopic hysteresis loop and local switching parameters, we used the nematic liquid crystal method to visualize domain structure dynamics in electric fields. The ‘triple-like’ shape of hysteresis loop observed near the ferro- to paraelectric phase transition has a strong link to the configuration of ferroelectric microdomains and compositional disorder in DGPI crystals.

Crystal growth and characterization of Deuterated Glycine Phosphite single crystals

Deuterated Glycine Phosphite single crystals were grown by low temperature solution growth method using high purity deuterated water as solvent. Deuteration content of the as grown crystals was improved by repeated recrystallisation process. Structural perfection, transparency and the functional groups present in the grown crystals were identified using different characterization analyses. Dielectric behaviors of the as grown specimens were examined through thermal and impedance analysis. Partial deuteration of the grown crystal was confirmed from the DSC and dielectric results.

Isotope Effect of Glycinium Phosphite NH3CH2COOH·H2PO3Studied by Neutron Diffraction

To study the isotope effect of glycinium phosphite (GPI), temperature dependences of the 5 0 \bar6 and 3 0 \bar10 structure factors of GPI and the 11 0 \bar3 and 9 0 \bar8 structure factors of deuterated GPI (DGPI) were analyzed in the ferroelectric phase by using the quasi-one-dimensional Ising model. The Ising model reproduces well the behavior of all the structure factors in the wide temperature region. The parameters for the intrachain and interchain interactions are determined to be 312 and 7.1 K for GPI, and 477 and 8.4 K for DGPI on average, respectively.

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

Deuteration effects on the critical relaxation in hydrogen-bonded ferroelectric glycine phosphite have been examined by the measurements of the complex dielectric constants along the ferroelectric b-axis of a series of partially deuterated crystals. The dielectric dispersion for crystals of low deuteration molar fraction was found to be composed of two Cole-Cole types with clearly different relaxation times. The shorter relaxation time shows a nearly classical mean-field exponent and the relaxation time at the temperatures with the same distance fromT C increases monotonically with the fraction similarly to the deuteration in CsH2PO4. The longer relaxation time decreases with the fraction.

Ferroelectric Phase Transition Character of Glycine Phosphite

The phase transition of glycine phosphite (GPI) and partially deuterated glycine phosphite (DGPI) single crystals has been characterized by applying the effective mean field theory. Temperature dependence of the spontaneous polarization P s(T) has been analyzed from hysteresis loops for these crystals. With the increment of deuteration ratio, saturated spontaneous polarization P s 0 is also increased. As a result, the quantitative phase transition indicator g according to the mean field theory is being increased but the maximum increment is underlying the decisive tricritical point g = 1/3. The phase transition character of GPI crystal is proved to be second order but very near to the tricritical point.

Fabrication of field effect transistor based on deuterated glycinium phosphite crystal and pentacene

We have fabricated a field effect transistor (FET) based on an organic ferroelectric insulator, a deuterated glycinium phoshite (D-GPI) and a pentacene film and have investigated electrical properties on the prepared FETs. It is observed that the FET based on D-GPI and pentacene film becomes a normally-on p-type FET. Moreover, we have observed that the gate electric field E G dependence of drain current i DS in the prepared FET displays the characteristics of hysteresis. This result indicates that the FET based on the D-GPI and pentacene film shows a memory effect Furthermore, we have found that the area of the i DS -E G hysteresis curve in the FET based on the D-GPI and pentacene film is determined by the magnitudes of the spontaneous polarization and coercive electric field of the D-GPI. On the basis of these results, it is also ascertained that the spontaneous polarization in the D-GPI insulator is responsible for the surface charge at the interface between the D-GPI and pentacene film. Furthermore, these results indicate that the values of i DS and the formation of the depletion layer largely depend on the spontaneous polarization and coercive field of the D-GPI insulator. Moreover, it is deduced that we can control the appearance of the depletion layer by controlling the deuterated ratio, which is responsible for the spontaneous polarization and coercive field of GPI insulator.

Neutron Diffraction Study of Crystal Structures of Deuterated Glycinium Phosphite in Paraelectric and Ferroelectric Phases

Crystal structure of deuterated glycinium phosphite was studied in the paraelectric (P) phase at 348 K and in the ferroelectric (F) phase at 223 K by means of the single crystal neutron diffraction. Deuteration rate is estimated to be 0.939 by the least-squares refinement. In the P phase, quasi-one-dimensional hydrogen bond chains are built by mutually linking the DPO 3 2- anions through two different types of hydrogen bonds with the bond angles of 179.2 and 171.6°. Two independent deuterons within the hydrogen bonds forming the chains are disordered over two sites separated by 0.545 and 0.539 Å. In the F phase, they order at a position nearly equal to one of two sites related by the disorder in the P phase. With the ordering of the deuterons, the P–O bonds with covalently bonded deuteron elongate, and those without covalently bonded deuteron reduce their lengths to some extent from the values determined in the P phase. Two oxygens involved in the hydrogen bond with the bond angle 179.2° exhibits especially large displacements in the F phase. This suggests strongly an importance of this hydrogen bond in the polarization appearance and in the ferroelectric transition. Comparison with results of non-deuterated salt indicates that only the hydrogen bonds forming the chains show significant isotope shift. In particular, the hydrogen bond with the bond angle 179.2° exhibits the most pronounced shift on the angle parameter defined by the angle between the line connecting two sites of disordered proton or deuteron and the line connecting two oxygens involved in the hydrogen bond.

Effect of Internal Bias Field on 180° Domain Switching in Deuterated Glycine Phosphite

The switching process in deuterated glycine phosphite crystal (DGPI) has been investigated by microscopic observation of domain structure using nematic liquid crystal (NLC) decoration technique and by switching current registration in high electric fields. The stabilization mechanism of 180° domains appears to have a correlation to a defect—induced internal bias field in the crystal.

Influence of Uniaxial Pressure on the Phase Transition of Partially Deuterated Glycinium Phosphite

Influence of uniaxial pressure on the phase transition of glycinium phosphite crystal has been studied by measurement of the permittivity along the b-axis. The pressure was applied to the crystal along the three principal axes a*, b and c. It has a tendency that the phase transition temperature shifts towards lower temperature with increasing uniaxial pressure. The uniaxial pressure dependence of the each principal axes on the phase transition temperature of 75% deuterated GPI crystal is dTC D75%/dpa*= −0.07 K/kbar for the a* -axis, dTC D75%/dpb= −2.57 K/kbar for the b-axis and dTC D75%/dpc = −1.33 K/kbar for the c-axis, respectively.

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.

Structural Study of Partially Deuterated Glycinium Phosphite in the Paraelectric Phase

The crystal structures of deuterated glycinium phosphite crystals with various deuterium concentrations x (0.00, 0.25, 0.50, 0.75 and 1.00) in the paraelectric phase were determined using the X-ray imaging plate diffractometer. The hydrogen bond distances increase with increasing deuterium concentration x , especially including the disordered hydrogen atom. There is a linear relation between the transition temperature T C and the hydrogen bond distance R O–O . The critical bond length r c was estimated as 2.415 A. HPO 3 tetrahedron rotates by duteration.

Ferroelectric Properties of Deuterated Glycine Phosphite

Ferroelectric Properties of Deuterated Glycine Phosphite

Ferroelectric Properties of Deuterated Glycine Phosphite

In order to investigate the effect of deuteration on the ferroelectric properties of glycine phosphite, single crystals with various deuteration ratio x (0 ∼ 0.78) have been prepared. The crystal form is not affected by the deuteration. Internal bias fields influenced hysteresis loops in all samples cut from crystals. Temperature dependence of permittivity of all samples shows a dielectric anomaly characteristic of the second order ferroelectric phase transition. The reciprocal permittivity strictly fulfills the Curie-Weiss low in each paraelectric phase. The transition temperature T C increases with the ratio x from 224K ( x = 0) to 320K ( x = 0.78). The transition temperature of fully deuterated crystal ( x = 1) is roughly estimated to be about 350K. The Curie constant is slightly affected by the deuteration.

Temperature study of the elastic properties of glycinium phosphite and deuterated glycinium phosphite crystals by brillouin scattering

Brillouin spectroscopy was used to study the elastic properties of glycinium phosphite (GPI) and deuterated glycinium phosphite (DGPI) crystals. The temperature measurements of the hypersonic velocity for acoustic modes propagating in various directions have been performed in the temperature range 170 K-300 K and 295 K-355 K for GPI and DGPI, respectively. Brillouin study has confirmed the existence of the order-disorder type ferroelectric phase transition (P21/a - P21) at 224 K for GPI and 322 K for DGPI. The obtained results are also discussed in terms of the reordering of the hydrogen bonds in the ferroelectric phase.

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.

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.