Faculty Publications
Permanent URI for this communityhttps://idr.nitk.ac.in/handle/123456789/18736
Publications by NITK Faculty
Browse
18 results
Search Results
Item Crystal structure of semiorganic antimony thiourea bromide monohydrate crystals: a redetermination(2009) Upadhya, M.K.; Udayashankar, N.K.The growth of antimony thiourea bromide monohydrate (ATBM) single crystals by evaporation technique at room temperature is reported here. Antimony thiourea bromide monohydrate crystallizes in the orthorhombic space group Cmca with unit cell parameters a = 12.320(7) A, b = 11.668(7) A, c = 18.615(11), and z = 8. The structure has been solved by direct methods and refined to a final R value of 0.0239.Item Electron irradiation effects on optical properties of semiorganic antimony thiourea bromide monohydrate single crystals(2010) Mahesha Upadhya, K.; Udayashankar, N.K.Antimony thiourea bromide monohydrate (ATBM) single crystals were grown by solution growth technique at room temperature for the first time. The UVvis, FT-IR and fluorescence spectra were recorded and electron irradiation effects on these properties were studied. The optical absorption edge of the UVvis spectrum shifts towards lower wavelength with the increase of irradiation. The fluorescence quantum yield is increased for electron irradiated ATBM crystals. The FT-IR analysis shows that the water of crystallization is weakly bonded in as-grown and electron irradiated ATBM crystals. © 2010 Elsevier B.V. All rights reserved.Item Synthesis, microhardness, FT-IR, and thermal decomposition of semiorganic antimony thiourea bromide monohydrate single crystals(2012) Mahesha Upadhya, K.; Udayashankar, N.K.Antimony thiourea bromide monohydrate (ATBM) single crystals were grown by a solution growth technique at room temperature. Microhardness studies on the grown crystal were carried out using the Vickers microhardness tester to estimate the mechanical strength of the crystal. The FT-IR analysis ascertains the presence of a metal-sulphur bond in ATBM crystals. The thermal decomposition of ATBM crystals was investigated by means of thermogravimetric analysis. © Springer Science+Business Media, LLC 2011.Item Electron irradiation effects on optical properties of semiorganic antimony thiourea tetra chloride single crystals(2012) Mahesha Upadhya, K.; Udayashankar, N.K.; Ganesh, S.Antimony thiourea tetra chloride single crystals were grown by solution growth technique at room temperature. The UV-visible, fourier transform infrared and fluorescence spectra were recorded and electron irradiation effects on these properties were studied. The optical absorption edge of the UV-visible spectrum slightly shifts towards longer wavelength with the increase of irradiation dose. The fluorescence quantum yield is decreased for electron irradiated antimony thiourea tetra chloride crystals. The presence of functional group of the as-grown and electron irradiated complex was confirmed by fourier transform infrared spectral study. © 2012 Elsevier B.V. All rights reserved.Item Synthesis, structural, optical and electrical (DC) properties of a semiorganic Thiourea Barium Chloride (TBC) single crystal(Elsevier GmbH journals@elsevier.com, 2017) Mahendra, K.; D'Souza, A.; Udayashankar, N.K.In the present study, TBC single crystals were synthesized using solution evaporation method. The structural analysis of TBC crystal was studied using Powder X-ray diffraction. Optical properties of TBC crystals were carried out using UV–vis, FTIR, Raman and photoluminescence (PL) spectra. The crystal shows absorbance maxima at 209 nm and transparent in the visible region 300–900 nm. The various optical constants such as refractive index, reflectance, speed of light, extinction coefficient, electrical susceptibility, dielectric constant, optical and electrical conductivity were evaluated. Thus results revealed that all these optical constants shows a strong dependence on optical absorption coefficient. Using single oscillator model (Wemple ?Didomenico), lattice dielectric constant and the ratio of free charge carrier to their effective mass were evaluated. The PL study of TBC crystals shows two emission peaks (419 nm ?S, 441 nm- Ba) in blue region. The DC resistivity and conductivity of the crystal was investigated in the temperature range 26 °C–115 °C. © 2017 Elsevier GmbHItem Effect of Zn doping on the structural, optical, photoluminescence and mechanical properties of thiourea barium chloride (TBC) crystal(Elsevier Ltd, 2017) Mahendra, K.; D'Souza, A.; Udayashankar, N.K.In the present work, a synthesis and comparative study on the effect of Zinc (Zn) on thiourea barium chloride (TBC) single crystals has been reported. Crystals of thiourea barium chloride and Zn-doped thiourea barium chloride crystals are prepared using slow evaporation from the saturated solution. The samples were subjected to single crystal and powder X-ray diffraction to study the unitcell parameters and structural variations. The functional groups present in the crystals are derived using FTIR and Raman analysis. The enhancement of transmittance with the addition of Zn and the variations in the parameters such as bandgap, extinction coefficient, reflectance, refractive index, optical and electrical conductivity, real and imaginary part of dielectric constant are studied from UV–vis spectrum analysis. Vickers hardness measurements are conducted for pure and Zinc-doped TBC single crystals. The emission spectrum of pure and Zn doped single crystals are studied using photoluminescence analysis. © 2017 Elsevier LtdItem Gamma irradiation effect on structural, optical and electrical properties of organometallic potassium hydrogen oxalate oxalic acid dihydrate single crystal(Springer New York LLC barbara.b.bertram@gsk.com, 2018) Mahendra, K.; Nayak, K.K.; Fernandes, B.J.; Udayashankar, N.K.Potassium oxalate oxalic acid dihydrate (KHO) single crystals were grown from solvent evaporation technique at room temperature. Crystals were optically characterized using UV–Vis and photoluminescence analysis. The gamma irradiation effects on KHO crystals were also studied optically and the results were analyzed to compare the effect of irradiation on the crystal lattice for different dosage. Structural variations were studied using powder XRD, FTIR and the results were examined to study the defect states created inside the lattice due to irradiation and the effect on the functional vibrations of the host crystal. Surface morphology of the crystal was studied using scanning electron microscope (SEM). Photo conductivity of the synthesized crystals were studied and analyzed to compare the photo response as well as the conductivity of the materials when subjected to irradiation. © 2018, Springer Science+Business Media, LLC, part of Springer Nature.Item Enhanced structural, optical, thermal, mechanical and electrical properties by a noval approach (nanoparticle doping) on ferroelectric triglycine sulphate single crystal(Springer Verlag service@springer.de, 2019) Mahendra, K.; Kumar, H.K.T.; Udayashankar, N.K.The pristine and AgNP-doped TGS crystals are studied using powder X-ray diffraction, density measurements, solubility studies, UV–Vis analysis, photoluminescence spectroscopic analysis, thermal gravimetric analysis, differential thermal analysis, differential scanning calorimetry, Vicker’s hardness measurements, I–V and impedance measurements. From the XRD studies, TGS crystal formation is confirmed and by further analyzing X-ray diffraction data it is noticed that the incorporation of nanoparticles induce stress in the lattice of TGS crystal, which, in turn, lead to shift in peak positions. Crystal solubility and density values are increased after doping process. From the emission spectrum it is evident that emission intensity increases as the doping concentration increased. The melting point and mechanical hardness of the crystals also showed improvement after AgNP doping. Band gap calculated by Tauc’s relation is found to decrease with increase in doping concentration. Further, electrical studies demonstrated that crystal conductivity is improved as the doping concentration increases. © 2019, Springer-Verlag GmbH Germany, part of Springer Nature.Item Modulations of physio-chemical and electronic properties of metalorganic KHO single crystals through Co(OH)2 nanoparticles doping(Springer New York LLC barbara.b.bertram@gsk.com, 2019) Mahendra, K.; Bhat, K.S.; Nagaraja, H.S.; Udayashankar, N.K.Semiorganic crystals play vital role in the design and development of optical devices. In this context, we report the synthesis of metalorganic potassium hydrogen oxalate oxalic acid dihydrate (KHO) single crystals using slow solvent evaporation technique. Further, Co(OH)2 nanoparticles pre-synthesized using hydrothermal method are doped to KHO single crystals. Doping of Co(OH)2 nanoparticles in the crystal system were confirmed through XRD, EDAX and PL measurements. The XRD measurements indicate a shift in the peak positions and variation in the overall intensities. On the other hand, PL measurements also indicate enhanced emission peaks confirming the successful doping of Co(OH)2 nanoparticles in the KHO system. As the effect of doping, the declination in the optical bandgap and improvement of electronic conductivity were also observed. © 2019, Springer Science+Business Media, LLC, part of Springer Nature.Item Growth and comparative studies on oxalic acid dihydrate, potassium oxalate hydrate and potassium hydrogen oxalate oxalic acid dihydrate single crystals(Elsevier Ltd, 2020) Mahendra, K.; Udayashankar, N.K.Single crystals of Oxalic acid dihydrate (OAD), Potassium oxalate hydrate (KOH), Potassium hydrogen oxalate oxalic acid dihydrate (KHOOD) were grown using solvent evaporation technique. Unit cell parameters of the crystals were studied using single crystal XRD (SCXRD) and the crystal parameters were found to match with the reported values. Structural properties were studied using powder XRD analysis. Optical absorption studies were carried out to determine the light absorption by the crystal and the optical bandgap was also calculated using Tauc's relation. Emission and thermal properties of the OAD, KOH and KHOOD crystals were studied using photoluminescence spectroscopy (PL) and TGA-DTA measurements respectively and explained in detail. Electrical studies were also carried out to find the resistivity of the material. The hardness of the synthesized crystal was also explored and the parameters such as stiffness constant, yield strength, fracture toughness and brittleness were evaluated and compared. © 2019 Elsevier Ltd