P. Rajesh

Interesting growth features in potassium dihydrogen phosphate: unravelling the origin and dynamics of point defects in single crystals

In a potassium dihydrogen phosphate single crystal grown by the temperature-lowering technique, some interesting growth features revealing the origin of point defects, their agglomeration and dynamics were observed. High-resolution X-ray diffractometry was employed for in-depth studies of the observed defects. Since the crucial properties of crystal-based devices are very much influenced by such defects, this is an important experimental finding with respect to improving growth techniques or conditions to avoid such defects.

Optical, dielectric and microhardness studies on 100 directed ADP crystal

(100) directed ammonium dihydrogen phosphate single crystal has been grown using the uniaxially solution-crystallization method of Sankaranarayanan-Ramasamy (SR). The size of the grown crystal is 40 mm in diameter and 50mm in thickness. The grown crystals were characterized by UV-vis spectroscopy, Vickers hardness and dielectric studies. Comparing the (100) plane of the conventional method grown ADP crystal with (100) directed SR method grown ADP crystal, optical transparency, dielectric constant and Vickers hardness number are increased and dielectric loss is decreased in SR method grown crystal.

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.

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.

Investigation on the solubility, crystal growth, optical, laser damage threshold, NLO, photoluminescence and dielectric properties of pure and cadmium (Cd2+)-doped lithium sulfate monohydrate single crystals

Single crystals of pure and cadmium-doped lithium sulphate monohydrate (LSMH) have been grown from aqueous solution by slow evaporation solution growth technique. The effect of metallic incorporation (Cd2+) on the crystal growth and characteristic properties of LSMH single crystal was studied. The grown crystals are subjected to powder X-ray diffraction studies to explore the structural properties of the pure and doped crystals. The dopant concentration of the crystal is estimated by inductively coupled plasma-optical emission spectroscopy. The crystal showed a 20% transmission enhancement on doping with Cd. Photoluminescence studies showed a violet fluorescence emission peak at 395 nm. The photoluminescence intensity of Cd-doped LSMH increased significantly to about 1.5 times that of pure LSMH. Laser damage threshold value and second-harmonic conversion efficiency of the grown crystals has been determined using Nd:YAG laser operating at 532 and 1064 nm, respectively. The multiple shot surface laser damage thresholds for pure and Cd-doped LSMH are found to be 6.9 GW/cm2 and 8.6 GW/cm2, respectively. Low dielectric loss and high dielectric constant shows that the grown crystal contains minimum defects.

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.

Growth and characterization of pure and doped KHP NLO single crystals.

Single crystals of Potassium Hydrogen Phthalate doped with amino acid l-lysine were grown successfully by slow evaporation method. The concentration of dopant in the mother solution was 0.5mol%, 1mol% and 2mol%. There is a drastic change in the morphology due to variation in doping rates which is also reflected in the X-ray diffraction data. The Fourier Transform infrared spectroscopy study confirms the incorporation of l-lysine into Potassium Hydrogen Phthalate crystal. The thermal study indicates the dissociating nature of the crystal. The nonlinear optical property of the grown crystal has been confirmed by Kurtz-powder second harmonic generation test. The dopant of 0.5mol% and 1mol% shows higher second harmonic generation result than pure Potassium Hydrogen Phthalate. Results are discussed.

Growth and characterization of organic NLO material: clobetasol propionate.

Single crystals of clobetasol propionate (CP) have been grown by slow evaporation solution technique using mixed solvent of methanol-acetone. The grown crystals were subjected to single crystal X-ray diffraction analysis to confirm their lattice parameter and space group. The powder X-ray diffraction pattern of the grown CP has been indexed. Thermal analysis was performed to study the thermal stability of the grown crystals. Photoluminescence spectrum shows broad emission peak observed at 421 nm. Nonlinear optical studies were carried out for the grown crystal and second harmonic generation (SHG) efficiency was found in the crystal.

Investigations on the growth, structural, optical, mechanical, dielectric and SHG behaviour of GPMG crystals

Abstract Glycinium picrate mono glycine crystals have been grown by slow evaporation solution technique and Sankaranarayanan–Ramasamy (SR) method. The size of the grown crystal in slow evaporation method was 15 × 3 × 2 mm3 and in SR method it was 15 mm in diameter and 38 mm in length. The grown crystals were subjected to crystal structure, single crystal X-ray diffraction, powder X-ray diffraction, High Resolution X-ray diffraction, Etching, UV–Vis, dielectric, mechanical and non-linear optical studies. The crystals grown by SR method have 90% of transmittance and the crystals grown by slow evaporation method has 65% of transmittance. In order to determine mechanical strength of crystal, Vickers micro-hardness measurement was carried out. SR method grown crystals has higher hardness. Dielectric study reveals higher dielectric constant and low dielectric loss for SR method grown crystal. The second harmonic efficiency of grown crystal is higher compared to pure KDP.