Faculty Publications

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Author: search.filters.author.Udayashankar, N.K.Subject: search.filters.subject.Barium compounds

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    Effect of alkali earth oxides on hydroxy-carbonated apatite nano layer formation for sio2 –bao–cao–na2 o–p2o5 glass system
    (Springer Science and Business Media Deutschland GmbH, 2017) Kiran, P.; Ramakrishna, V.; Shashikala, H.D.; Udayashankar, N.K.
    Barium soda lime phosphosilicate [(58SiO2– (32-x)BaO–xCao–6Na2 O–4P2O5 (where x = 15, 20, 25 and 30 mol%)] samples were synthesised using conventional sol–gel method at 700 °C sintering temperature. Thermal, structural properties were studied using thermo gravimetric analysis and differential thermal analysis, X-ray diffraction, scanning electron microscopy, fourier transform infrared and Raman spectroscopy. Using Raman spectra non-bridging oxygen concentrations were estimated. The hydroxy-carbonated apatite (HCA) layer formation on samples was analysed for 7 days using simulated body fluid (SBF) soaked samples. The growth of HCA layers self-assembled on the sample surface was discussed as a function of NBO/BO ratio. Results indicated that the number of Ca2? ions released into SBF solution in dissolution process and weight loss of SB-treated samples vary with NBO/BO ratio. The changes in NBO/BO ratios were observed to be proportional to HCA forming ability of barium soda lime phosphosilicate glasses. © Springer. All rights reserved.
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    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 Ltd
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    Synergistic enhancement of optical properties in erbium-doped borate glasses through copper nanoparticle incorporation
    (Elsevier Ltd, 2024) Ingle, A.; Shashikala, H.D.; Udayashankar, N.K.
    The present study investigated the impact of incorporating copper nanoparticles (CuNPs) on the optical properties of erbium-doped borate glasses. Through melt-quenching and heat treatment techniques, glasses with varying Cu2O concentrations (x = 0–5 mol%) were synthesized. Physical and structural analyses revealed that Cu ions serve as effective network modifiers. They foster the formation of a greater proportion of BO4 tetrahedra and thus enhancing glass homogeneity. Optical absorption spectra demonstrate a distinct modulation of Er3+ absorption bands with Cu2O embedding, indicating the formation of CuNPs, as validated by the emergence of surface plasmon resonance bands. This structural evolution results in a noticeable reduction in the bandgap energy, signifying improved semiconducting behavior. Judd-Ofelt analysis highlighted the profound influence of CuNPs on hypersensitive transitions, thereby affecting oscillator strength. Photoluminescence measurements revealed amplified emission in the visible red and near infrared (NIR) region, attributed to the synergistic effects of CuNPs and Er3+ ions, with 5 mol % Cu2O exhibiting the highest emission intensity. Analysis of the radiative properties validates the enhancement of the emission cross-section, gain bandwidth, optical gain and radiative transitions. These enhancements contribute to a notable increase in the branching ratio from 0.91 % to 5.41 % accompanied by an increase in the quantum efficiency from ∼79 % to ∼90 %. Moreover, decay analysis revealed a notable enhancement in lifetime from 3.03 ms to 15.74 ms, which is indicative of enhanced radiative transitions. Overall, the incorporation of CuNPs into erbium-doped borate glasses facilitates significant enhancements in physical, structural, and optical properties. This positions them as promising materials for a wide array of optoelectronic applications. This comprehensive study sheds light on the complex interplay between CuNPs and erbium-barium borate glasses, offering valuable insights for the development of advanced optoelectronic materials with enhanced performance and functionality. © 2024 Elsevier Ltd and Techna Group S.r.l.