P. Ramasamy

Thermoluminescence characteristics and dosimetric aspects of fluoroperovskites (NaMgF3:Eu2+,Ce3+)

Abstract The perovskite-like NaMgF3 polycrystalline powder samples, pure and rare earth doped, were synthesized by conventional solid state reaction method. The perovskite material was doped with 0.2 mol.% of EuF3 and CeF3 impurity. Phase purity of synthesized compounds was analyzed by powder X-ray diffraction technique. The thermoluminescence response of polycrystalline samples showed a linear response up to 12 Gy and then became sub linear at higher doses. The order of kinetics (b), activation energy (E) and other trapping parameters were calculated using peak shape method and variable heating rate method. From glow curve analysis the symmetric factor was calculated. The glow curve showed two peaks at 404 and 488 K, and both of them confirmed the thermoluminescence in the phosphor, which obeyed second-order kinetics. The experimental resulted showed that this phosphor could have potential applications in radiation dosimetry.

Synthesis, growth and spectroscopic investigation of an organic molecular charge transfer crystal: 8-hydroxy quinolinium 4-nitrobenzoate 4-nitrobenzoic acid.

An organic intermolecular charge transfer complex salt of 8-Hydroxy quinolinium 4-nitrobenzoate 4-nitrobenzoic acid (OPNB) has been synthesized. Single crystals of OPNB were grown by slow solvent evaporation solution growth technique at room temperature. The (1)H and (13)C NMR spectra were recorded to confirm the molecular structure of the complex salt. The crystal structure of OPNB has been determined by single crystal XRD analysis and it belongs to triclinic crystal system with space group P-1. Fourier transform infrared (FT-IR) spectral study has been carried out to identify the various functional groups present. The UV-Vis-NIR transmittance spectrum was recorded in the range 200-2500nm, to find the suitability of the single crystal for various optical applications. The thermal stability of the crystal was investigated using thermogravimetric (TG) and differential thermal analyses (DTA).

Growth, structural, thermal, optical, and electrical properties of potassium succinate–succinic acid crystal

Potassium succinate–succinic acid (KSSA), semi-organic single crystals were grown by slow evaporation growth technique using water solvent. Single crystal X-ray diffraction study revealed that the KSSA crystal belongs to monoclinic system. FT-IR and FT-Raman spectral studies were performed to identify the vibrations of functional groups. TGA/DTA analyses were carried out to characterize the melting behavior and stability of the title compound. The UV–Vis–NIR spectrum showed that the grown crystal is transparent in the entire visible region. Fluorescence studies were carried out in the range of 200–700xa0nm. The optical nonlinearity of KSSA was investigated at 532xa0nm using 7xa0ns laser pulses, employing the open aperture Z-scan technique. The photoconductivity study was carried out to know the conducting nature of the crystal. The laser damage threshold was measured using Q-switched Nd:YAG laser (1064xa0nm). Electrical properties of the crystal are studied using Hall Effect measurement.

Synthesis, growth, spectral, and thermal studies of a new organic molecular charge transfer complex crystal: 3-Nitroaniline 4-methyl benzene sulfonate

A new organic intermolecular charge transfer complex 3-nitroaniline 4-methyl benzene sulfonate (NATS) has been successfully synthesized and good optical quality single crystals grown by slow solvent evaporation solution growth technique at room temperature using methanol as the solvent. The (1)H and (13)C NMR spectra were recorded to establish the molecular structure of the title complex. The crystal structure of NATS has been determined by single crystal XRD analysis and it belongs to orthorhombic crystal system with space group Pbca. Fourier transform infrared (FT-IR) spectral study has been carried out to confirm the presence of various functional groups present in the complex. Electronic absorption spectrum was recorded to find the prevalent charge transfer activity in the complex. The UV-Vis-NIR transmission spectrum was recorded in the range 200-2500 nm, to find the optical transmittance window and lower cut off wavelength of the title crystal. The thermal stability of the title complex crystal was studied by using thermo-gravimetric and differential thermal analyses and found that the compound is stable up to 215 °C.

Crystal growth, spectral, optical, laser damage, photoconductivity and dielectric properties of semiorganic L-cystine hydrochloride single crystal.

The semiorganic single crystals of l-cystine hydrochloride have been grown by slow evaporation solution growth technique at 40°C. The grown crystals were subjected to single crystal XRD, FTIR, optical absorbance, laser damage threshold, photoluminescence, photoconductivity and dielectric studies. Single crystal XRD studies reveal that the crystal belongs to monoclinic system with space group C2 and the lattice parameters are a=18.63 (Å), b=5.28 (Å), c=7.26 (Å), α=90°, β=103.70°, γ=90° and V=696 (Å(3)). FTIR spectroscopy confirms that a band at 1731 cm(-1) represents characteristic of α-amino acid hydrochlorides. The UV-Vis-NIR absorption spectrum was analyzed and the optical band gap energy was found to be 3.8eV. The crystal exhibits sharp emission peak at 388 nm. The thermal characteristics of crystals were studied by TG-DTA, which indicate that there is no weight loss up to 201°C. Surface laser damage threshold value of title compound was estimated using high power Q-switched Nd:YAG laser operating at 1064 nm. Dielectric and photoconductivity studies were also carried out for the grown crystals.

Study on structural, morphological, optical and thermal properties of guanidine carbonate doped nickel sulfate hexahydrate crystal

The single crystal of guanidine carbonate doped nickel sulfate hexahydrate was grown from solution for ultraviolet filters. The single crystal XRD confirms that the grown single crystal belongs to the tetragonal system with the space group of P4₁2₁2. The crystallinity of the grown crystal was estimated by powder X-ray diffraction studies. The optical transmission and thermal stability of as-grown guanidine carbonate doped nickel sulfate single crystals have been studied. The optical transmission spectrum demonstrates the characteristics of ultraviolet filters. The TG/DTA studies confirm the thermal properties of grown crystals. Thermo-gravimetric analysis showed that the dehydration temperature of the guanidine carbonate doped nickel sulfate crystal is about 100 °C, which is much higher than that of pure nickel sulfate hexahydrate (NSH) crystals which is 72 °C. The growth behaviors and dislocation density were detected under the high resolution XRD and etching studies respectively.

Growth and characterization of propyl- para -hydroxybenzoate single crystals

Single crystals of propyl-p-hydroxybenzoate have been grown by slow evaporation solution technique. The structure of the compound was confirmed by FT-IR, FT-Raman spectroscopy and single crystal X-ray diffraction studies. The crystalline perfection of the grown single crystals has been analysed by high resolution X-ray diffraction measurements. Optical properties of the grown single crystals were studied by UV-Vis NIR spectrum. The luminescence behaviour of the single crystal has been analysed by photoluminescence analysis and found maximum luminescence in the lower wavelength region. A simple interferometric technique was used for measuring birefringence of the crystal. The laser damage threshold of the crystal is 1.3 GW/cm2. The mechanical strength of the grown crystal is measured using Vickers microhardness tester. The dielectric properties have been investigated.

Synthesis, growth, structural, optical and thermal properties of an organic single crystal: 4-Nitroaniline 4-aminobenzoic acid

The organic single crystals of 4-nitroaniline 4-aminobenzoic acid (4NAABA) were grown from ethanol solvent. The lattice parameters of the grown crystal have been confirmed from single crystal XRD analysis. The powder XRD pattern shows the various planes of grown crystal. The FTIR and (1)H NMR spectral analysis confirm the presence of various functional groups and the placement of proton in 4NAABA compound respectively. The UV absorption was carried out which shows the cutoff wavelength around 459 nm. The optical band gap of the crystal has been evaluated from the transmission spectra and absorption coefficient by extrapolation technique. In addition, a fluorescence spectral analysis is carried out for 4NAABA crystals. The thermal properties of crystals were evaluated from thermogravimetrical analysis. It shows that the grown crystal is stable up to 160°C and the crystal has sharp melting point at 151°C.

A study on Fourier transform infrared spectroscopy, thermal, mechanical, NLO and laser damage properties on unidirectional Glycinium Picrate Mono Glycine crystal.

By directional solidification, single crystal of Glycinium Picrate Mono Glycine (GPMG) was successfully grown by Sankaranarayanan-Ramasamy (SR) method. An optically transparent crystal of GPMG has been grown along 〈011〉 plane by a mixed solvent of acetone and double distilled water. The evaporation rate was controlled and a single crystal of 12mm diameter and 35mm length was obtained. Single crystal X-ray diffraction, Fourier Transform Infrared Spectroscopy (FTIR), thermal, mechanical, SHG and laser damage studies were carried out. The results are discussed in detail.

Thermal and FTIR spectral studies of various proportions of zinc magnesium ammonium sulfate

Mixed crystals of various proportions of zinc magnesium ammonium sulfate were grown by slow evaporation of aqueous solution at room temperature. The bright and transparent crystals obtained were characterized through thermal (TG–DTA) and FTIR spectral analyses. A fitting decomposition pattern for the compound was formulated on the TG curve which shows two stage mass losses between 133 and 478.75xa0°C. DTA curve shows exothermic peaks in this temperature range supporting the formulated decomposition pattern. The FTIR spectra show the vibration frequencies due to the formation of zinc magnesium ammonium sulfate mixed crystals. Detailed structural analysis of the compound is under progress.