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Cuddapah, India

Sivaramaiah G.,Government College for Men | Lakshmanarao J.,Sri Venkateswara University
Journal of Alloys and Compounds | Year: 2013

Electron Spin Resonance and optical absorption spectral studies of Cu 2+ ions in 5 Al2O3 + 75 B2O 3 + (20-z) PbO + z CuO (where z = 0.1-1.5 mol.% of CuO) glasses have been reported. The EPR spectra of all the glasses show resonance signals characteristic of Cu2+ ions at both room and low temperatures. The number of spins and Gibbs energy were calculated at different concentrations and temperatures. From the plot of the ratio of logarithmic number of spins and absolute temperature and the reciprocal of absolute temperature, the entropy and enthalpy have been evaluated. The optical absorption spectra of all the glasses exhibit three bands and these bands have been assigned to 2B 1g → 2Eg, 2B1g → 2B2g, and 2B1g → 2A1g transitions in the decreasing order of energy. It is for the first time to observe three optical absorption bands for Cu2+ ions in oxide glasses. Such type of results is due to excellent sample preparation. From the EPR and optical absorption spectroscopies data, the molecular orbital coefficients have been evaluated. © 2012 Elsevier B.V. All rights reserved. Source


Kumar A.G.S.,Sri Krishnadevaraya University | Obulapathi L.,Annamacharya institute of Technology and science | Maddaiah M.,P.A. College | Sarmash T.S.,Sri Krishnadevaraya University | And 4 more authors.
AIP Conference Proceedings | Year: 2015

The Cd doped ZnO have versatile applications in the field of solar cells, Optoelectronic devices. The Cd doped ZnO thin films were prepared by reactive dc magnetron sputtering at different O2 Partial Pressures (1-3sccm) on glass substrate. The structure of the compound was determined by XRD, the mictro structure was studied by FE-SEM, the absorption spectra studies were measured with UV-Vis-NIR spectrometer and electrical properties were studied by four probe method. The optical band gap was variation reported in this study. The minimum resistivity found at PO2=2.0sccm. © 2015 AIP Publishing LLC. Source


Sivaramaiah G.,Government College for Men | Rao J.L.,Sri Venkateswara University
Proceedings of the Indian National Science Academy | Year: 2012

Using the electron paramagnetic resonance data of VO2+ and Cr+3centers in alkali lead borotellurite glasses, the thermodynamic properties such as Gibbs free energy AG, entropy AS and enthalpy AH have been evaluated. The effect of temperature, concentration and alkali ions on Gibbs free energy is studied for VO2+ and Cr3+ centers in alkali lead borotellurite glasses. It is observed that the Gibbs free energy has increased with the increase of concentration and temperature. The Pauli magnetic susceptibility is calculated at different temperatures ( 123-433 K) for VO 2+ center in lithium lead borotellurite glass. The Pauli magnetic susceptibility is also calculated for Cr3+center in potassium lead borotellurite glass at different temperatures (123-313 K). The pre-exponential coefficient (PEC) is calculated from the logarithmic of number of spins and the reciprocal of absolute temperature graph of VO2+and Cr3+ centers in alkali lead borotellurite glasses. The preexponential coefficient indicates the collision frequency between the transition metal ion and the glass lattice. The relaxation time Tm or T2, is determined from the number of spins and the temperature effect on relaxation time has been studied for the two ions. The Gibbs free energy, pre-exponential coefficient, Pauli magnetic susceptibility, relaxation time are compared between VO 2+ and Cr3+centers in alkali lead borotellurite glasses. These values are also compared between alkali ions in alkali lead borotellutite glasses. © Printed in India. Source


SivaRamaiah G.,University of Saskatchewan | SivaRamaiah G.,Government College for Men | Pan Y.,University of Saskatchewan
Physics and Chemistry of Minerals | Year: 2012

Samples of a natural amethyst, pulverized in air, and irradiated for gamma-ray doses from 0.14 to 70 kGy, have been investigated by powder electron paramagnetic resonance (EPR) spectroscopy from 90 to 294 K. The powder EPR spectra show that the surface Fe 3+ species on the gamma-ray-irradiated quartz differ from its counterpart without irradiation in both the effective g value and the observed line shape, suggesting marked radiation effects. This suggestion is supported by quantitatively determined thermodynamic properties, magnetic susceptibility, relaxation times, and geometrical radius. In particular, the surface Fe 3+ species on gamma-ray-irradiated quartz has larger Gibbs and activation energies than its non-irradiated counterpart, suggesting radiation-induced chemical reactions. The shorter phase-memory time (T m) but longer spin-lattice relaxation time (T 1) of the surface Fe 3+ species on the gamma-ray-irradiated quartz than that without irradiation indicate stronger dipolar interactions in the former. Moreover, the calculated geometrical radius of the surface Fe 3+ species on the gamma-ray-irradiated quartz is three orders of magnitude larger than that of its counterpart on the as-is sample. These results provide new insights into radiation-induced aerosol nucleation, with relevance to atmospheric cloud formation and global climate changes. © 2012 Springer-Verlag. Source


Siva Ramaiah G.,Government College for Men
Proceedings of the Indian National Science Academy | Year: 2011

From electron paramagnetic resonance data of Fe3+ and Mn 2+ ions in alkali lead tetraborate glasses, the thermodynamic potentials such as Gibbs potential AG, entropy of activation AS, enthalpy of activation AH have been evaluated. The effect of temperature, concentration and alkali ions on Gibbs potential is studied for Fe3+ and Mn 2+ ions in alkali lead tetraborate glasses. It is observed that the Gibbs potential has increased with the increase of concentration and temperature. The Pauli magnetic susceptibility is calculated at 296 K and different temperatures (123-393 K) for Fe3+ and Mn2+ ions in alkali lead tetraborate glasses. The pre-exponetial coefficient is calculated from the logarithmic of number of spins and the reciprocal of absolute temperature graph of Fe3+ and Mn2+ ions in alkali lead tetraborate glasses. The pre-exponential coefficient indicates the collision frequency between the transition metal ion and the glass host lattice. The phase memory relaxation time Tm (T2) and the spin-lattice relaxation time T1 were calculated for the two ions. The temperature effect of the relaxation times was studied for the two ions. The Gibbs potential, pre-exponential coefficient, Pauli magnetic susceptibility, relaxation times were compared among Fe3+ and Mn2+ ions in alkali lead tetraborate glasses. These values were compared among alkali ions in alkali lead tetraborate glasses. © Printed in India. Source

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