TGS Crystals Research Articles

The Temperature Changes of Refractive Indices and Thickness of Doped Triglycine Sulfate Crystals

The temperature dependences of the optical path difference δΔi and the relative changes in the thickness δli/l of TGS crystals doped with L-threonine are studied. The temperature dependences of the relative changes in the refractive indices δni/(n – 1), coefficients of anisotropy for refractive indices, and linear expansion have been calculated. Characteristic minimum has been detected on these curves near the phase transition temperature.

The effect of impurity on temperature variations in the refractive indices and thickness of TGS crystals

Temperature dependences of optical path difference δΔі and the relative changes in thickness δlі/l of TGS crystals doped with L-valine are studied. Temperature dependences of the relative changes in refractive indices δnі/(n–1) are calculated. The anisotropy coefficients of refractive indices Аn–1(Т) and linear expansion Аα(Т) are calculated, and a characteristic minimum of these dependences is found near the phase transition temperature.

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.

Optical properties of D-serine doped TGS crystals for pyroelectric sensors

AbstractRefractive and birefringence indices in the range of transparency of 300 to 700 nm for triglycine sulphate crystals doped with D-serine molecules have been measured in the temperature range of 290 K to 340 K. The obtained optical properties are discussed together with characteristic electrical features of these materials used as pyroelectric sensors for measurement of temperature. The experimental results obtained in this study will be necessary as the reference data for comparison with the calculated refractive indices of TGS + D-serine on the basis of density functional theory. Determination of the proper position of D-serine, will reveal the features of TGS + D-serine crystal structure necessary to achieve stable unipolarity.

Role of Bias Electric Field for X-ray Diffraction Intensity by TGS Crystal in Transverse Electric Field

X-ray diffraction intensity of triglycine sulfate single crystals influenced by the transverse electric field has been measured in the bias electric field. Polarity of domains in the sample can be judged by variation in intensity associated with polarity of the bias field. Polarity of the domains does not change by the bias field after prolonged transverse field application. There seems to be still positive domains even in the negative bias field and vice versa. Polarity of the domains seems to be randomly aligned without any relation to polarity of the bias field after the prolonged application.

Electronic band structure and optical properties of ferroelectric TGS, TGSe and TGFB crystals

Structural and electronic properties of the ferroelectric TGS, TGSe and TGFB crystals were studied by the ab initio method in the framework of the density functional theory. Equation of state (total energy vs. unit cell volume), band structure, density of electronic states and dielectric functions in the range of valence electrons excitations have been calculated using the plane waves and pseudopotentials. The comparable structural and electronic characteristics of TGS, TGSe and TGFB crystals are obtained for the first time and discussed in relation to the reference experimental data. The semiempirical dispersion-correction approach implemented in CASTEP code has been applied to the materials studied and has been shown to produce results more close to the experimental data. Correlation of the total energy difference Ep – Ef for paraelectric and ferroelectric phases and Curie temperatures of the ferroelectric phase transitions has been revealed for TGS, TGSe and TGFB crystals, that was not reported before.

Theoretical Study of Ferroelectric Triglycine Sulphate (TGS) Crystal in External Electric Fields

A modified two sub-lattice pseudospin-lattice coupled mode model of Mitsui et al [Phys. Rev., 111 (1958) 1259] by adding third, fourth order phonon anharmonic interaction and external electric field terms has been applied to ferroelectric triglycine sulphate crystal. Electric field dependence of ferroelectric, dielectric and acoustical properties has been studied. With the help of double time temperature dependent Green’s function method, expressions for shift, width, soft mode frequency, dielectric constant, loss tangent and acoustic attenuation have been derived. Numerically calculations have been made and results have been compared with experimental data reported by Bye et al [Ferroelectrics 4 (1974) 243] and Shreekumar et al [Ferroelectrics 160 (1994) 23] for TGS crystal and a good agreement has been observed.

Size-driven ferroelectric–paraelectric phase transition in TGS nanocomposites

Dielectric properties of porous glass nanocomposites with TGS crystals embedded into six porous matrices with average pore size from 5 to 312 nm were investigated in the temperature range from 280 to 380 K at selected frequencies. The results are discussed based on the effect of the particle size on the phase transition temperature of TGS nanocomposites. Temperature–size phase diagram of TGS composites was derived. Non-monotonic character of the temperature-driven phase transition (T p) with the decreasing particle size was determined. The nature of the T p variation can be ascribed to the size-effect theoretically predicted by Zhong et al. (Phys Rev B 50:698–703, 1994).

Theoretical Study of Ferroelectric Triglycine Sulphate (TGS) Crystal in External Electric Fields

A modified two sub-lattice pseudospin-lattice coupled mode model of Mitsui et al [Phys. Rev., 111 (1958) 1259] by adding third, fourth order phonon anharmonic interaction and external electric field terms has been applied to ferroelectric triglycine sulphate crystal. Electric field dependence of ferroelectric, dielectric and acoustical properties has been studied. With the help of double time temperature dependent Green’s function method, expressions for shift, width, soft mode frequency, dielectric constant, loss tangent and acoustic attenuation have been derived. Numerically calculations have been made and results have been compared with experimental data reported by Bye et al [Ferroelectrics 4 (1974) 243] and Shreekumar et al [Ferroelectrics 160 (1994) 23] for TGS crystal and a good agreement has been observed.

Ferroelectric field-effect transistor based on ZnO:Li/LiNbO3 and ZnO:Li/TGS heterostructures for IR pyrodetectors

We have developed and studied a new type of pyroelectric IR photodetector based on ferroelectric-field-effect transistor heterostructures with higher sensitivity and detectability than traditional pyroelectric photodetectors. Model samples of ferroelectric field-effect transistor were prepared using ZnO:Li films as a transistor channel and LiNbO3 or TGS crystals as a pyroelectric sensitive element.

Crystal growth and characterization of 4-(dimethylamino)benzaldehyde doped TGS crystals

Crystal growth and characterization of 4-(dimethylamino)benzaldehyde doped TGS crystals

Effect of swift heavy ion beam irradiation on the dielectric and ferroelectric properties of pure and cobalt doped TGS crystals

Effect of swift heavy ion (100 MeV O 7+ ion) beam irradiation on the temperature and frequency dependence of real ( ε′) and imaginary ( ε″) parts of dielectric permittivity in pure and Co 2+ doped TGS crystals are analyzed. Irradiation with swift heavy ion beam changes the dielectric response considerably. Observed dielectric peak in irradiated crystals shifts towards lower temperature and broadens up; the reduction in peak value, shift in temperature and broadening changes systematically with fluence. The most interesting results of SHI irradiation are (i) the dielectric loss peak value ( e max ″ ) in all crystals is invariably less in comparison to the value in unirradiated crystals (ii) the minimum value of dielectric loss peak ( e max ″ ) occurs at different fluence in different crystals, and (iii) a second loss peak is observed below T c in CTGS10 especially at higher fluence. It seems that irradiation creates/strengthens internal field in the crystals by orienting the domains through some mechanism that is not clear at present. The observed results could be explained if one presumes that irradiation annihilate the defects already present in the crystals by creating local charges and thermal gradient resulting into internal bias field. Ferroelectric hysteresis loops demonstrate the internal bias field developing in the SHI irradiated crystals. It is argued that SHI irradiation is a better alternate in comparison to cobalt doping in inhibiting dipolar switching in TGS crystal.

The calculation of absolute piezooptic constants of TGS crystals with L-treonine admixture

The calculation of absolute piezooptic constants of TGS crystals with L-treonine admixture

Birefringence of mechanically clamped TGS crystals with L-valine admixture

Birefringence of mechanically clamped TGS crystals with L-valine admixture

About the spontaneous electrooptical effect of TGS crystals admixtured with D-serine

About the spontaneous electrooptical effect of TGS crystals admixtured with D-serine

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.

Studies on the effect of l-glutamine on morphology, structure, optical, mechanical and electrical properties of TGS crystal

Single crystals of l-glutamine doped triglycine sulfate (LGTGS) were grown from aqueous solution by low-temperature solution growth technique using slow cooling method. The LGTGS crystals exhibit prominent morphological changes in the (1 0 1) and (0 1 0) planes. Lattice parameter values were determined by single-crystal XRD analysis. The powder X-ray diffraction confirms the crystalline nature of LGTGS. The presence of dopants in the crystal lattice was qualitatively confirmed by FTIR analysis. The UV–vis–NIR spectrum was recorded to study the optical transparency of the grown crystals. Microhardness studies were carried out using Leitz Weitzler hardness tester at room temperature. The dielectric studies were carried out to identify the phase transition temperature and the dielectric behavior. The P– E hysteresis loops were recorded at 50 Hz to find the values of spontaneous polarization ( P s) and coercive field ( E c).

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.

Analysis of polarization switching in ferroelectric crystals in the injection mode

We report on the results of experiments on polarization switching in a ferroelectric TGS crystal during injection of electron beams from a scanning electron microscope under a surface layer. A series of models reflecting the polarization switching dynamics of a ferroelectric crystal under the action of an injected charge is constructed. The implementation of these models is based on the principles of evolution of domain structures taking into account analysis of possible polarization switching mechanisms for ferroelectric samples. A mathematical model developed using these principles demonstrates qualitative similarity of model current pulses and those obtained experimentally in the injection mode.

Influence of Defects on the Relaxation of Non-Equilibrium Domain Structure in TGS Crystals

The relaxation of non-equilibrium domain structure in TGS-family crystals was studied by measurements of time dependences of the pyroelectric coefficient at different temperatures below a Curie point. Role of the impurity defects results in the different character of temperature dependences of a relaxation time and in the influence of an internal bias field that governs the domain structure evolution and determines both a sign and a value of crystal unipolarity.