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925 results on '"Veeraiah, N."'

3. Nonlinear optical birefringence in Li2SO4-MgO-P2O5 amorphous system-influence of Cu ions

Author

Reddy, A. Siva Sesha, Kityk, A. V., Jedryka, J., Rakus, P., Wojciechowski, A., Sekhar, A. Venkata, Kumar, V. Ravi, and Veeraiah, N.

Subjects
Condensed Matter - Materials Science, Physics - Chemical Physics
Abstract

Li2SO4-MgO-P2O5 glasses doped with varied contents of CuO (from 0- 1.0 mol%) were prepared. The optical birefringence induced by a High Q-2 femtosecond pulsed laser is explored as a function of copper oxide concentration in these glasses. The magnitude of the light-induced birefringence exhibited a gradual decrease with the increase of copper oxide content. The observed behavior is discussed in terms of polymerization of the glass network, the degree of which rises with concentration of Cu+ ions occupying Td sites in the glass matrix. However, the samples containing low content of CuO are dominated by Cu2+ ions that act as modifiers and induce structural imperfections by breaking of P-O-S bonds. Accordingly, the samples mixed with lower content of CuO are more favorable for inducing higher magnitudes of the optical birefringence. This conclusion is corroborated by results of electrical conductivity, positron annihilation and ultrasonic measurements., Comment: 6 pages, 3 figures

Published
2022
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4. The anisotropic photorefractive effect in lithium sulfo-phosphate glass system doped with nickel ions

Author

Reddy, A. Siva Sesha, Kityk, A. V., Jedryka, J., Purnachand, N., Rakus, P., Wojciechowski, A., Andrushchak, A. S., Kumar, V. Ravi, and Veeraiah, N.

Subjects
Physics - Optics, Physics - Chemical Physics
Abstract

In this work, nonlinear optical (NLO) studies of nickel oxide doped (ranging from 0.2 to 1.0 mol%) Li2SO4-MgO-P2O5 glasses are reported. A combination of femtosecond (fs) laser, as a pumping light source and a high-accuracy polarimeter with low power probing laser, is used to investigate the light-induced optical anisotropy (OA) in these glass materials. The light-induced birefringence (LIB) exhibits slow relaxation tendency up to about 10 s suggesting on anisotropic photorefractive effect evidently dominated fast Kerr effect. This behavior is evaluated in the light of other results reported recently and is explained by the glass polymerization mechanisms. The photorefractive birefringence increases with increase of the quantity of NiO up to 0.8 mol% and it is attributed to the enhanced degree of depolymerization of the glass network due to the hike in the concentration of Ni2+ ions that occupy octahedral (Oh) positions. Further increase of NiO content (>0.8 mol%) causes, however, a certain decrease of the photorefractive birefringence. Notable change in concentration trend is interpreted by rising of phonon losses due to increasing portion of the nickel ions occupying tetrahedral (Th) sites that facilitates the polymerization of the glass network. The doped glasses with the NiO content of about 0.8 mol% may be considered as optimal in the sense of photorefractive efficiency. Relevant samples exhibit largest magnitudes of the photorefractive birefringence and appear to be favorable for potential applications., Comment: 5 pages, 4 figures

Published
2022
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5. Investigation of the effect of Au2O3 dopant on elastic properties of PbO-B2O3-SeO2: Er2O3 glass ceramics by ultrasonic techniques

Author

Reddy, A. Siva Sesha, Kityk, A. V., Jedryka, J., Rakus, P., Wojciechowski, A., Venkatramaiah, N., Kumar, V. Ravi, and Veeraiah, N.

Subjects
Condensed Matter - Materials Science, Physics - Chemical Physics
Abstract

Various elastic coefficients of Au2O3 doped PbO-B2O3-SeO2:Er2O3 (PBSE) glass ceramics were evaluated as functions of Au2O3 content using ultrasonic velocity measurements. The elastic coefficients and micro-hardness showed a decreasing tendency with the concentration of Au2O3. Such decrease is attributed to the increasing concentration of gold metallic particles and [SeO3]2- groups that acted as modifiers and induced imperfections in these samples. Obtained results were observed to be consistent with the conclusions drawn from spectroscopic studies that include X-ray photoelectron spectroscopy (XPS), infrared (IR), photoluminescence (PL) and positron annihilation (PAL) spectroscopy studies. Overall, these studies have revealed that even though, the presence of gold metallic particles is preferable for achieving superior luminescence and electrical properties, presence of such particles caused to decrease the elastic coefficients and micro-hardness of these glass ceramics. However, when the concentration of Au2O3 is increased beyond 0.075 mol%, we have observed a slight increase of elastic coefficients and micro-hardness., Comment: 6 pages, 8 figures

Published
2022
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21. Studies on dielectric features of Li2O-Ga2O3-SiO2: Cr2O3/MoO3/WO3 glass systems.

Author

Krishna, S. Vijaya, Pavić, L., Bafti, A., Pisk, J., Bhadrarao, D., Rao, Y. Dana, Sekhar, A. Venkata, Kumar, V. Ravi, and Veeraiah, N.

Subjects
GLASS, DIELECTRIC properties, PERMITTIVITY, DIELECTRICS, LIGHT absorption, ALUMINUM-lithium alloys
Abstract

This investigation consists of results of the studies on dielectric properties and a.c. conductivity of Li2O-Ga2O3-SiO2 (LGS) glass with 2.0 mol% of Cr2O3, MoO3, WO3 across 0.01 Hz to 1 MHz and 20 °C to 240 °C. Structural analysis using optical absorption and IR spectra indicated dopant ions predominantly in Cr3+, Mo6+/Mo5+, W6+ states, and occupied Td and Oh positions. Dielectric constant and conductivity were found to be the maximal for LGSMo glass, with the lowest impedance, while LGSCr glass exhibited the opposite trend. From the analysis of dipolar relaxation effects probable dipoles were identified in each glass. Studies on conductivity revealed that contribution of ionic components is very low and a substantial polaronic contribution in LGSMo glass, whereas, LGSCr glass showed a larger ionic component, specifically Li+ ion diffusion and hence more useful material for solid-state batteries with respect to the other two glasses. [ABSTRACT FROM AUTHOR]

Published
2024
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35. Spectroscopic properties of holmium ion in PbO–B2O3–SiO2–Al2O3 glass system.

Author

Sri Pallavi, A. V., Sahaya Baskaran, G., Purnachand, N., Little Flower, G., Ravi Kumar, Valluri, and Veeraiah, N.

Abstract

The glasses of the composition 30PbO–60B2O3–5.5SiO2–(4.5 − x) Al2O3–xHo2O3 (with x varied from 0 and 2 mol%) were prepared. Density (ρ), refractive index (n), and average molecular weight (M) were calculated from experimental measurements of these glasses. The spectra of optical absorption besides the photoluminescence were recorded at room temperature in the wavelength range of 300–2200 nm and 450–2200 nm, respectively. Using the optical absorption spectra the oscillator strengths were estimated and found to be in good agreement with the theoretical values evaluated using optical absorption spectra. Glasses doped with 0.5 mol% holmium had the highest bonding parameter, while those doped with 2.0 mol% holmium had the lowest. From this observation, it was concluded that holmium ions are in a more covalent environment in H20 glasses. The overall analysis of the luminescence spectral results indicated maximal luminescence efficiency of the glasses with 0.5 mol%. [ABSTRACT FROM AUTHOR]

Published
2024
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