Pure TGS Research Articles

Studies on the Temperature Stability of Pure and Doped Triglycine Sulphate Crystals Using TGA/DTA

Aim: To study the temperature stability of TGS doped with ZnSO4, CdCl2, BaCl2, and compare it with that of pure TGS. Objectives: Synthesizing pure and doped TGS and studying their temperature dependence using TGA, DTA, and DSC analysis. Methods: Slow cooling solution growth was used to grow single crystals of pure and doped TGS. The TGA, DTA and DSC analysis was conducted for determining the temperature stability. Results: The thermal analysis of pure and doped TGS shows that the doped samples show a similar dependence on temperature as pure TGS. The temperature of decomposition of pure and doped samples (BTGS, ZTGS, CdTGS) was 226.60°C, 228.38°C, 229.13°C, and 239.13°C respectively. The melting onset of these samples was 214.51°C, 216.04°C, 217.69°C and 216.04°C respectively. Conclusion: The study shows that doping TGS with the above three described materials did not alter their temperature stability considerably. It is a good result as doping TGS, for varying its characteristics like absorbance, reflectance, bandgap energy, etc., which did not alter its temperature stability. Therefore, TGS doped with the above three dopants can be used at the same temperature ranges as of pure TGS but with much-improved efficiency.

Influence of a static magnetic field on the dielectric properties of triglycine sulfate

The influence of a static magnetic field on the permittivity ε of pure TGS crystals has been studied. There is no of the magnetic effect when the vectors B and PS are collinear, it exists when B and PS are mutually orthogonal and it is greater when B is oriented along a-axis. After the magnetic field is turned off, the values of ε first increase up to the maximum observed of about 30–40 h, and then a long recovery to the initial values of ε occurs. Possible mechanisms of influence of the magnetic field on the studied crystals are discussed.

Peculiarities of the Dielectric Spectra of Triglycine Sulfate Crystals with a Profile Distribution of Chromium

The temperature evolution of the dielectric spectra of TGS–TGS + Cr crystals (TGS stands for triglycine sulfate) with a periodic distribution of chromium impurity (Cr3+) has been studied in comparison with nominally pure TGS crystals in the frequency range from 10 to 107 Hz upon heating and cooling. It is shown that impurity crystals are characterized by the absence of dielectric dispersion in both measurement modes. An approach is proposed to explain the peculiarities of the dielectric dispersion of crystals with a periodic distribution of chromium impurity from the standpoint of mobile activity of certain elements of the TGS crystal structure.

Enhanced ferroelectric properties and crystal structure of TGS0.74P0.26 single crystals

The single crystals of triglycine sulpho phosphate (TGS0.74P0.26) were grown by slow evaporation method with 0.6 M of phosphoric acid in the growth solution. The crystal structure of the grown crystal is refined with 0.74 sulphur and 0.26 phosphorous occupancy with the formula of TGS0.74P0.26 using single crystal x-ray diffraction analysis. The dielectric, ferroelectric and pyroelectric properties of the TGS0.74P0.26 single crystals were investigated. The coercive field (Ec) and internal bias field (Ib) values are 8 kV/cm and 1.4 kV/cm, respectively and these values are found increased compared to the pure TGS and also low dielectric loss was observed. The pyroelectric coefficient of TGS0.74P0.26 crystal is 0.023 µC/cm2/°C and the pyroelectric figure of merit for current, voltage and detectivity are Fi = 105 pm/V, Fv = 0.055 m2/C and Fd = 22 µPa−1/2 respectively. Enhanced ferroelectric properties were observed when compared to the pure TGS crystals. The figure of merit for the detectivity (Fd) shows higher values when compared with that of the well-known materials such as PZT (11.5 µPa−1/2) and other lead free materials such as SBN (7.21 µPa−1/2) and CSBN (12 µPa−1/2). With these excellent properties, the TGS0.74P0.26 single crystal can be a promising material for the pyroelectric detector applications.

Structural, FTIR and Ferro electric analysis of pure TGS and L-Cysteine doped TGS crystals for infrared device applications

Abstract This paper aims at investigating the line broadening of powder X-ray diffraction peaks as a result of compositional disorder in L -Cysteine doped triglycine sulfate crystals. Various methods such as Williamson-Hall and size-strain plot methods were used in this study. The analysis indicates that L -Cysteine substitution in triglycine sulfate crystals results in anisotropic strain in the crystal. The crystalline quality and cell parameter values were found using XRD analysis. The presence of L -Cysteine in TGS was estimated qualitatively by Fourier transform infrared analysis. The ferroelectric nature of the crystals was identified by P–E hysteresis loop analysis.

Thermal and surface studies of unidirectional grown nickel sulfate added triglycine sulphate single crystal

Triglycine sulfate crystal added with 0.5 mole% nickel sulfate of 15 mm diameter and 150 mm height has been grown from an aqueous solution using Sankaranarayanan–Ramamasamy (S‐R) method in [001] direction. The grown crystal was studied by various characterization techniques. Thermogravimetry analysis reveals that the NiSO4 added TGS crystal is more thermally stable than pure TGS crystal. The presence of nickel in the TGS‐NiSO4 crystal was confirmed by atomic absorption spectroscopic (AAS) technique and its concentration was found to be 284 ppm. The surface of the grown crystal was investigated using atomic force microscope (AFM). It revealed the surface defects of the doped TGS crystal.

Optical, dielectric & ferroelectric studies on amino acids doped TGS single crystals

Pure TGS and amino acid (l-arginine, l-histidine and l-alanine) doped TGS crystals were grown by a slow evaporation solution growth technique at room temperature.

Performance of crystal violet doped triglycine sulfate single crystals for optical and communication applications

Single crystals of 0.01 and 0.02 mol% crystal violet dye doped triglycine sulfate (NH2CH2COOH)3·H2SO4 (TGS) have been grown by a slow evaporation technique. Enhanced dielectric, optical, thermal and mechanical properties have been achieved by dye doping. Monoclinic structures showing particular coloring patterns and morphology change with dye concentration were obtained. Various functional groups and dye incorporation in the grown crystals were confirmed qualitatively by FTIR and Raman analysis. A significant increase in Curie temperature from 50 to 55 °C with a decrease in maximum permittivity has been observed. The UV-vis spectra showed an increased transmittance window and an increased optical band gap from 5.61 to 6.11 eV as a result of doping. An increase in the sharpness and intensity of the photoluminescence peak with a blue shift has been observed in doped crystals. The thermal stability and the decomposition temperature were found to increase by about 10 °C in 0.01 mol% dye doped TGS. The mechanical strength of the grown crystals was estimated by the Vickers microhardness test and was found to be high for dye doped TGS. A high piezoelectric charge coefficient d33 of 16 pC N−1 was observed for pure TGS which decreased as a result of the dye effect. The fabrication of a patch antenna was carried out after simulating its resonant frequency, making it suitable for telecommunication applications.

Effects of Triglycine Sulphate on Ferroelectric Behavior of Ammonium Dihydrogen Phosphate Crystals

Pure ADP and TGS doped ADP crystals were grown successfully in aqueous solution using the conventional slow evaporation technique. The structural characteristics of the grown crystals were examined by power X-ray diffraction spectroscopy. The results confirm that the samples were single crystalline with some additional planes when adding TGS dopant in the solution. Also, the results from the FT-IR show the presence of TGS in the grown ADP crystal. However, the addition of TGS did not show a strong influence on the dielectric nor the ferroelectric properties of the TGS doped ADP. Higher concentrations of TGS may be needed to improve both the dielectricity and ferroelectricity properties of ADP single crystals.

MgCl2 added triglycine sulphate crystals

Single crystals of pure and MgCl2-added triglycine sulphate crystals were grown from aqueous solutions by low temperature solution growth technique. From the powder XRD technique crystal system remains same (Monoclinic) and the unit cell parameters are slightly different from the pure TGS. FTIR and FT-Raman spectra were recorded to identify the vibrational activity of the various functional groups present in the title crystals. To determine the concentration Mg 2+ ion in the MgCl2added triglycine sulphate crystals inductively coupled plasma optical emission spectrometer (ICP-OES) study was carried out. The amount of MgCl2 (mol %) incorporated into the crystal is very low, a factor of 10 -2 in comparison to the actual amount taken in the solution. UV-VIS-NIR study shows that there is wide transparency in the visible region and the band gap energies were calculated. The mechanical strength of the grown crystals were known by hardness numbers and work hardening coefficient values. Dielectric constant and dielectric loss of the crystals were studied as function of frequency. Copyright © 2011 VBRI press.

Iminodiacetic acid doped ferroelectric triglycine sulphate crystal: Crystal growth and characterization

Single crystals of iminodiacetic acid (HN(CH 2COOH) 2) doped triglycine sulphate (IDATGS) crystals have been grown from aqueous solution containing 1–10 mol% of iminodiacetic acid at constant temperature by slow evaporation technique. The effects of different amounts of doping entities on the growth habit have been investigated. X-ray powder diffraction pattern for pure and doped TGS was collected to determine the lattice parameters. The grown crystals were subjected to Fourier transform infrared (FTIR) spectroscopy studies to find the presence of various functional groups qualitatively. The dielectric permittivity has been studied as a function of temperature. An increase in the transition temperature (49.2–49.7 °C) of IDATGS crystals is observed. The dielectric constant ( ε′ max) of IDATGS crystals vary in the range 922–2410 compared to pure TGS ( T c=49.12 °C and ε′ max=3050). Curie Weiss constants C p and C f in the paraelectric and ferroelectric phases were determined. The transition temperature ( T c) is found to decrease with increase in dopant concentration. P– E hysteresis studies show the presence of internal bias field in the crystal. Piezoelectric measurements were also carried out at room temperature. Domain patterns on b-cut plates were observed using scanning electron microscope. The micro hardness studies reveal that the doped crystals are harder than the pure TGS crystals. The low dielectric constant, higher transition temperature, internal bias field and hardness suggest that IDATGS crystals could be a potential material for IR detectors.

Improved ferroelectric and pyroelectric parameters in iminodiacetic acid doped TGS crystal

Single crystals of Iminodiacetic acid (HN(CH 2COOH) 2) doped Triglycine sulphate (IDATGS) has been grown from aqueous solution at constant temperature by slow evaporation technique. The concentration of the dopant in the TGS solution was 2 mol%. The X-ray diffraction analysis indicates that there is significant change in the lattice parameters compared to pure TGS crystal. The IDATGS crystal has larger transition temperature and observed higher and uniform figure of merit over most part of the ferroelectric phase. These crystals also exhibit higher internal bias field and micro-hardness number compared to pure TGS. Therefore IDATGS may be a potential material for IR detectors.

Raman Scattering and Electrical Properties of TGS:PCo (9%) Crystal as Ambient Temperature IR Detector

We developed and adequately characterized the triglycine sulfate family crystals doped with specific molar percent of cobalt phosphate, TGS:PCo (9%). The crystals were grown by slow evaporation technique and the growth rates of different crystallographic planes are rather faster in comparison with the plane growth rates of pure TGS crystals. The introduction of Co ion as an active optical element to the structure of TGS crystal leads to optimization of some parameters such as optical quality, stability at ambient condition, Curie temperature, stronger Raman peaks, etc. Three new peaks at 460, 620 and 1368 cm−1 were observed in the dispersive back scattering Raman spectra of the grown TGS:PCo (9%) crystal in comparison with the pure triglycine sulfate crystal.

Electron Emission from the Surface of TGS Crystals with Different Domain Structure

A relation was established between the emission signal magnitude and the domain structure type in nominally pure TGS crystals and TGS crystals with various impurities: europium and chrome ions. It was demonstrated that in non-unipolar samples with numerous domain walls an electron emission is either very weak or is absent at all. The obtained results can be explained in the framework of cold emission from ferroelectrics.

Swift heavy ion induced modification on the dielectric behaviours of pure and doped TGS crystals

Swift heavy ion beam irradiation has been used for creating the non-equilibrium condition in the ferroelectric crystals of TGS doped with alanine impurities. Dielectric measurements reveal that irradiated crystals retain their ferroelectric phase and Tc remains invariant. Dielectric peak, however, gets broaden and decreases with increasing fluence. Tangent loss also decreases. Dielectric dispersion in different crystals show interesting changes with fluence and is analyzed in terms of thermally generated electric field in the crystals that stabilizes the bi-domain structure.

The Refractive Properties of Uniaxially Stressed Doped TGS Crystals

The effect of uniaxial mechanical stresses applied along the principal crystal-physical axes on the principal values of birefringence Δ n i is studied on TGS crystals with L-threonine, L-valine and D-serine admixtures. It is revealed that Δ n i are quite sensitive to the stresses and have different values and opposite signs. The baric coefficients ∂Tc/∂ σm for the phase transition (PT) temperature appear to be smaller than those for the pure TGS crystals. Temperature and spectral dependences of the combined piezooptic constants are calculated.

Brillouin scattering studies of the ferroelectric phase transition in l-lysine doped TGS single crystals

The Brillouin spectroscopy study of triglycine sulphate crystals doped with l-lysine (TGSL10) has been performed. We observed longitudinal or quasi-longitudinal acoustic phonons propagating parallel to b, c and c ∗ ( c ∗ denotes direction perpendicular to the ab plane) crystal's axes. The temperature dependence of both frequency shift and the spectral line width have been investigated in temperature range 25–75 °C. Our results are similar to those obtained for pure TGS. The spectra of the acoustic modes propagating in c and c ∗ directions show step-like anomaly in frequency shift and an anomalous broadening of the line just below the transition temperature. This behaviour is in contrast to ‘the temperature independent’ quasi-longitudinal phonon propagating parallel to spontaneous polarization ( b-axis). The obtained results can be explained by (characteristic in the ferroelectric phase transition) influence of depolarization field effect of the long range dipole–dipole interaction. The relaxation time of polarization fluctuations in the vicinity of the phase transition has been estimated. The increase of the speed of relaxation process caused by lysine doping has been revealed.

Electron Emission from Irradiated Ferroelectrics

Decrease of thermostimulated exoelectron emission from the crystals of ferroelectric TGS was observed experimentally after X-ray irradiation with E q = 8 keV. Decrease of emission current occurred for all the investigated times of irradiation from 1 minute to 60 minutes. Samples under investigation were placed in series along the direction of X-rays propagation. Some of the samples were also obtained by cleaving of previously irradiated bar of TGS crystal. In both cases an increase of emission current j em was observed with decrease of irradiation dose. Dependence of j em on the linear heating rate of a sample q = dT/dt was studied. Under low rates of heating emission was observed only in ferroelectric phase. For high values of q = 5 K/min pulling of electron emission into paraphase takes place. For all the rates of heating the temperature of terminating of emission in the irradiated TGS is less as compared with pure TGS.

Thermostimulated Electron Emission in Paraelectric Phase of TGS Crystals with Nickel Admixture

Thermostimulated electron emission from ferroelectric TGS crystal with an admixture of nickel was experimentally detected in the temperature range exceeding Curie point by ∼10 K for the samples heated with rather high rate. An increase of the heating rate q was shown to result in an increase of the emission current in the entire investigated temperature interval. In TGS crystal with nickel admixture the temperature of emission appearance insignificantly depends on the rate q and is close to the case of pure TGS. The temperature of disappearance of emission monotonously increases with q. The interval of pulling of emission to paraphase here is less than for a case of pure TGS heated with the same rate. Peculiar features of emission in the investigated crystal can be explained by the relaxation of screening charges of spontaneous polarization. Less temperature of termination of the emission in TGS crystal with nickel admixture as compared with pure TGS crystal is explained by less Maxwell relaxation time in the doped crystal. The work was made under support of VZ-010 grant intended for creation of Research Educational Center “Wave processes in non-homogeneous and non-linear media” and INTAS grant “Ferroelectrics templated in nanoporous membranes.”

Kinetics of Electron Emission from Ferroelectrics

Kinetics of thermostimulated emission in ferroelectric crystals is examined. It is shown that in pure TGS crystals characteristic emission relaxation time depends on temperature, and decreases as one approaches the phase-transition point. The relaxation time of emission signals in crystals enriched with impurities is several times less than in pure materials and does not depend on temperature. Thermally stimulated electron emission is experimentally observed in TGS crystals, in a temperature range with upper limits of 10–15 𝒦 above the Curie point. The reason for the occurrence of emission above the Curie point is related to slow relaxation of the screening charges, which persist in the paraelectric phase.