Phase Transition In Triglycine Sulphate Research Articles

Pyroelectric response of single-crystal samples of trigycine sulphate in three dimensions

This study presents an investigation of the pyroelectric properties of single-crystal samples of triglycine sulphate (TGS) in 3D. The use of cubic samples and a suitable measurement setup made it possible to investigate the pyroelectric properties of TGS samples along the polar b axis and the mutually perpendicular directions to this axis. The measuring station was self-designed and constructed using a Keithley nanovoltmeter, a Rhode & Schwarz computer-controlled power supply, a GW INSTEK multimeter, a measuring chamber with Peltier cells, and a LabView custom user interface. Measurements of the pyroelectric response in 3D allowed us to conclude that the hydrogen bond between glycines G2-G3 may be strongly engaged in the phase transition in TGS, and is probably the trigger for the process. Our 3D investigation of the phase transition mechanism in single-crystal TGS is very promising in terms of research into the best pyroelectric materials for infrared thermal sensors.

Influence of moisture on ferroelectric–paraelectric phase transition of a composite containing oxidized MWCNT and TGS

This work reports experimental results for investigating the effects of residual water on phase transition in triglycine sulfate (TGS) filled with 5 wt% of oxidized multiwalled carbon nanotubes (OMWCNTs) under a relative humidity of 90% for different storage time. A similar composite containing TGS and non-oxidized MWCNT was also synthesized for comparison. According to measured data, the moisture was well adsorbed into OMWCNT/TGS composite and resulted in the shift of phase transition point toward higher temperatures for samples stored for less than 5 days. The longer storage caused a significant drop of dielectric constant at phase transition.

Phase transition in triglycine sulphate investigated using two-phase bridge measurements

The heterogeneity of the phase transition in triglycine sulfate (TGS) samples is investigated in this study, using a two-phase bridge and four-electrode sample setup. It is the practical continuation of our previous – theoretical works. Four-electrode samples and two-phase bridge measurements demonstrate interesting opportunities for observation of the dynamics of the blurred phase transition in two areas of the samples. In order to design and produce infrared sensors with desired properties it is crucial to understand the physical mechanisms and phenomena present in the investigated material. In model calculations, a characteristic peak of the bridge unbalance voltage is observed in the case of the phase transition temperature shift of less than 0.05 °C. Four-electrode samples were fabricated and bridge measurements were conducted for four frequencies and at a temperature range of 29–65 °C. Experimental results were compared with model calculations.

Phase transition in triglycine sulfate crystals by 1H and 13C nuclear magnetic resonance in the rotating frame

The ferroelectric phase transition in triglycine sulfate ((NH2CH2COOH)3·H2SO4, TGS)) crystals, occurring at TC of 322K, was studied using 1H and 13C CP/MAS NMR. From the spin–lattice relaxation time in the rotating frame, T1ρ, of 1H and 13C, we found that the slopes of the T1ρ versus temperature curve changed near TC. In addition, the change of intensities for the protons and carbons NMR signals in the ferroelectric and the paraelectric phases led to the noticeable changes in the environments of proton and carbon in the carboxyl groups. The carboxyl ordering was the dominant factor driving the phase transition. Our study of the 1H and 13C spectra showed that the ferroelectric phase transition of TGS is of the order–disorder type due to ordering of the carboxyl groups.

Diffuse scattering and the mechanism for the phase transition in triglycine sulphate

Despite the order/disorder nature of its ferroelectric phase transition, and evidence for the evolution of local order as being important for understanding the transition, no comprehensive diffuse scattering study of the short-range order in triglycine sulphate, (TGS), (NH2CH2COOH)3H2SO4 has been undertaken. Diffuse scattering from single crystals is sensitive to two-body correlations, and can act as a probe of local structure, which in a second order phase transition acts as a precursor to the low temperature phase. The role of hydrogen bonding and dipolar interactions in the ferroelectric phase transition in TGS has been a long matter of conjecture. Using neutron and X-ray single crystal diffuse scattering this study shows that hydrogen bond mediated interactions between polarising glycine molecules cause local one-dimensional polarised domains to develop, oriented parallel to the b axis. These domains interact via dipolar interactions, and the three-dimensional ferroelectric order arises. This provides a real-space, interaction-based model for the phase transition in TGS, showing in detail how the local chemistry and physics give rise to the polarised state.

Pressure induced structural phase transition in triglycine sulfate and triglycine selenate

To elucidate the cause of destruction of ferroelectricity with pressure in triglycine sulfate and triglycine selenate, we have investigated these compounds with the help of Raman measurements as well as first principles total energy and structural optimization calculations. Our results show that, beyond the critical pressures, the loss of ferroelectricity in these compounds is due to the conformational change in one of the three glycine ions of these crystals. Our studies suggest that pressure induced phase transition might be of displacive nature unlike the temperature induced ferroelectric phase transition in these crystals which is known to be of order-disorder type.

Ferroelectric phase transition in triglycine sulphate embedded into porous glasses

Properties of ferroelectric triglycine sulphate (TGS) confined within a porous glass were investigated. The results of dielectric, pyroelectric and thermal expansion measurements for glasses with different sizes of pores embedded with TGS are presented. A positive shift of the phase transition temperature inversely proportional to the pore dimension was observed. A negative shift of the phase transition temperature for methylammonium halogenoantimonate (MAPCB) embedded into porous glasses was determined based on the dielectric measurement results.

Effect of isotope substitution and pressure on the phase transition in triglycine sulphate

A quantitative estimate of dipolar interaction energy causing the order–disorder ferroelectric phase transition in triglycine sulphate (TGS) is obtained and also the effect of small hydrostatic pressures on the dipolar energy is modelled. At high pressures of the order of 2.5 GPa a crystallographic phase transition to a non-ferroelectric phase takes place in these crystals, the spontaneous polarization goes to zero most likely because of the glycine ion GI becoming planar at high pressures. The inverse Ubbelohde effect observed in TGS is successfully explained using the corrected valence bond model. The increase in transition temperature ( T C) on deuteration is associated with the increase in value of the reorientable dipole moment of TGS. A quantitative estimate of increase is obtained using the Mecke dipole function.

Scanning force microscopy study of the ferroelectric phase transition in triglycine sulfate

Voltage-modulated scanning force microscopy is applied to study the temperature dependence of the ferroelectric domain structure of triglycine sulfate up to TC, the ferroelectric transition temperature. The polarization image contrast exhibits a power-law decrease as TC is approached, associated with the competition between Maxwell stress and the converse piezoelectric effect. Substantial differences in the static and dynamic domain patterns are detected for two samples of different aging conditions.

The effect of electronic subsystem on the structural phase transition in triglycine sulphate

The influence of internal field Eb and X-ray radiation on the phase transition temperature Tc in TGS crystals is studied. Results of experiments make possible to separate the effect of bias field on Tc from that of electrons formed during X-ray irradiation. The influence of electrons upon Tc and Eb is more essential in crystals having greater number of imperfections.

Phase transition in triglycine sulphate studied by thermally-induced electric oscillations

Abstract The method of thermally-induced electric oscillations was employed in studying the temperature dependences of elastic and piezoelectric coefficients in TGS. The results are compatible with those reported in the literature. As shown previously, the crystal softens significantly in the vicinity of the phase transition. Having measured the amplitude of the oscillations, we found a temperature-activated contribution to the expected square-root dependence of the piezoelectric modulus. This effect has been attributed to the formation of paraelectric clusters. Close to the phase transition temperature, deviations from the exponential behavior have been found.

Optical properties of the triglycine sulphate group crystals in the 5 to 22 eV region

Abstract The optical constants of triglycine sulphate (TGS) and triglycine fluoroberyllate (TGFB) crystals have been determined in the 5 to 22 eV region. The changes of the optical constants during the phase transition in TGS have been described, the results obtained agree with certain principles of the vibronic theory of ferroelectricity.

Paramagnetic resonance study of fluctuations near phase transition in triglycine sulphate

The EPR line widths of the high and the low field resonances of Cr 3+ in triglycine sulphate (TGS) show two distinct anomalous broadenings near T c . One is associated with a change in the motional frequency of the hindered rotation of the NH 3 groups and the other is related to the fluctuation of the polarization. Just below T c there is a two fold splitting of the resonances which has a (T c −T ) 1 2 temperature dependence indicating the local geometry about the Cr 3+ ion is determined by mean field theory.

Electromechanical coupling of surface acoustic waves in the vicinity of the phase transition in triglycine sulfate

The temperature dependences of an effective piezoelectric constant have been determined in the vicinity of the Curie temperature in the presence of externally applied electric fields from simultaneous measurements of the temperature variations of the electromechanical coupling constant of surface acoustic waves and of the dielectric constant. It is shown that the experimental results can be explained on the assumption that piezoelectricity in triglycine sulfate is of an ’’induced’’ and not an ’’intrinsic’’ nature.

Brillouin Scattering Studies of the Uniaxial Ferroelectric Phase Transition in TGS and TGSe

The Brillouin spectra of the ferroelectric triglycine sulfate (TGS) and its isomorphous selenate (TGSe) crystals have been observed in three cases of orientations of the longitudinal or quasi-longitudinal phonon vector q ; (1) q // c -axis, (2) q // b -axis and (3) q deviates 5° from b -axis in the (100) plane. The temperature dependence of both the frequency shift and the spectral width shows a remarkable anisotropy near T c . In the case (1) the temperature at which the width becomes maximum shifts to the lower temperature than T c which has simultaneously been determined by an accompanied measurement of dielectric constant. The polarization relaxation time is determined from this temperature shift using the phenomenological relation. In the case (2) and the case (3), the decrease in the anomaly is explained as the depolarization field effect of the long range dipole-dipole interaction which is characteristic in the ferroelectric phase transition.

Pulsed Nitrogen—Proton Double Resonance Study of the Ferroelectric Transition in Triglycine Sulfate

The technique of nuclear magnetic pulsed double resonance in the rotating frame has been used to study the changes in the 14N quadrupole interactions in a triglycine sulfate (TGS) single crystal on going from the paraelectric to the ferroelectric phase. The 14N electric field gradient tensors have been determined above as well as below Tc. The most significant effect of the ferroelectric transition is a large change in the time averaged value of the C–N bond direction of glycine I and the onset of chemical nonequivalence of glycines II and III due to an ordering of the protons in the short O–H ··· O bond. The results show that the phase transition in TGS is of the order—disorder type as far as the glycine groups are concerned.

Optical Study of X-Ray Irradiation Effect on the Phase Transition in Triglycine Sulfate and Diglycine Nitrate

Infrared spectra are measured at various temperatures on ferroelectric triglycine sulfate (Tc=48°C) and diglycine nitrate (Tc=−67°C) and nonferroelectric diglycine hydrochloride, each of which includes a short hydrogen bond connecting two glycine molecules. Almost all of the spectra of these substances are only slightly changed as the temperature passes through the respective Curie points. In contrast, a band at 575 cm−1 in triglycine sulfate is very characteristically changed, and its behavior is strongly influenced by x-ray irradiation. Further, a detailed inspection of the spectra shows that above and below the respective Curie points one of the two glycine molecules is in zwitterion form in diglycine nitrate and not in triglycine sulfate, and that the potential for the proton is of symmetrical single-minimum type in the latter and of asymmetrical double-minimum type in the former. Based on these facts, it is suggested that the origin of the phase transition, in triglycine sulfate, is not attributable to the hydrogen bond but to the remarkable intensity behavior of the 575-cm−1 band. On the other hand, in diglycine nitrate it is ascribed to a collective motion leading to the interchanging of the hydrogens between two possible equilibrium positions on the hydrogen bonds.