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Nandigāma, India

Rao M.S.,Acharya Nagarjuna University | Sudarsan V.,Bhabha Atomic Research Center | Brik M.G.,University of Tartu | Gandhi Y.,Kakani Venkata Ratnam College | And 5 more authors.
Journal of Alloys and Compounds | Year: 2013

Emission features of Dy3+ ions were characterized as a function of Al2O3 concentration in lead silicate glasses. The emission spectra exhibited conventional blue, yellow, orange and red emission bands due to 4F9/2?6H15/2, 6H13/2, 6H11/2 and 6H9/2 transitions of Dy3+ ions, respectively. The intensity of all these bands exhibited increasing trend with increase in the concentration of Al2O3 and this increase was attributed to decrease of luminescence quenching due to declusterization of Dy3+ ions by Al3+ ions in the glass network. From the emission spectra, the radiative parameters viz., spontaneous emission probability A, the total emission probability AT, the radiative lifetime τρ, the fluorescent branching ratio b, of different transitions originated from 4F9/2 level of Dy3+ ions were evaluated. The Y (I4F9=2→6H11/2)=B(I4F9/2→6H15/2) integral emission intensity ratio of Dy3+ ions evaluated from the luminescence spectra, showed decreasing trend with increase in the concentration of Al2O3. The decrease of this ratio is explained basing on structural modifications taking place in the vicinity of the Dy3+ ion in the glass matrix. The CIE color coordinates for three glasses were evaluated and found to be in the yellow region. © 2013 Elsevier B.V. All rights reserved. Source


Rajeswara Rao D.,Acharya Nagarjuna University | Ramesh Babu P.,Acharya Nagarjuna University | Gandhi Y.,Kakani Venkata Ratnam College | Veeraiah N.,Acharya Nagarjuna University
Journal of Molecular Structure | Year: 2014

Pr3+ doped lead oxy fluoro borate glasses mixed with three sesquioxides (M2O>3) viz. Y2O3, Sc2O3, Al2O3 of different concentrations (0-10 mol%) have been synthesized. The preliminary understanding over the structural modifications due to the insertion of the sesquioxides in the glass network could be obtained by IR spectral investigations. The optical absorption, luminescence spectra and fluorescence decay curves of these glasses were studied as functions of concentration of M2O3. The luminescence spectra of these glasses have exhibited the bands due to 3P0 → 3F2, 3F3, 3H6, 3H4, 3H5 transitions of Pr3+ ions. From these spectra, the radiative parameters viz., spontaneous emission probability A, the total emission probability AT, the radiative lifetime τ, the fluorescent branching ratio β of different transitions originated from 3P0 level of Pr3+ ions have been evaluated. A considerable enhancement in the luminescence emission corresponding to 3P0 → 3H6, 3F2 transitions has been observed with increase in the concentraion of M2O3 up to 8.0 mol%. The increase has been attributed to the possible declusterization of Pr3+ ions by M3+ ions in the glass network. The comparison of emissive characteristics of the glasses mixed with three sesquioxides indicated the highest luminescence efficiency for Y2O3 mixed glasses among the three series glasses studied and this has been explained in terms of different degrees of variations in the structural modifications in the vicinity of Pr3+ ion in the glass network. © 2014 Elsevier B.V. All rights reserved. Source


Bhargavi K.,Acharya Nagarjuna University | Sanyal B.,Bhabha Atomic Research Center | Rao M.S.,Acharya Nagarjuna University | Kumar V.R.,Acharya Nagarjuna University | And 3 more authors.
Journal of Luminescence | Year: 2015

This paper reports thermoluminescence (TL) studies on PbO-Al2O3-SiO2: Pr3+glasses mixed with varying concentrations of Al2O3 exposed to γ-rays of doses varied between 0 and 5.0 kGy. The TL glow curves of the γ-ray irradiated samples exhibited a dosimetric peak at about 200 °C and the area under the curve increased with increasing Al2O3 and also with the γ-ray dose. The mechanisms responsible for TL emission are quantitatively discussed. The dose response of these glass samples exhibited linear behavior in the medium dose range viz., 1.0-3.0 kGy. Finally, it is observed that the glass mixed with 10 mol% of Al2O3 exhibits highest TL output. The reasons for such larger TL efficiency of these glasses have been identified and discussed quantitatively with the help of the results of optical absorption, IR and Raman spectroscopy. © 2015 Elsevier B.V. Source


Swamy B.J.R.S.,Acharya Nagarjuna University | Vijay R.,Acharya Nagarjuna University | Babu P.R.,Acharya Nagarjuna University | Sanyal B.,Bhabha Atomic Research Center | And 2 more authors.
Ionics | Year: 2016

γ-Ray-induced dielectric dispersion in CaF2–B2O3–P2O5 glasses doped with different concentrations of CuO was investigated. The glass samples were exposed to γ-rays with dose varying within the range 0–10 kGy. The dielectric dispersion and spectroscopic properties were measured before and after γ-ray treatment. Additionally, thermoluminescence studies were performed on post-irradiated glass samples. The results of dielectric properties and dielectric breakdown strength indicated a substantial increase in the insulating strength of CuO containing glasses due to γ-ray irradiation. The analysis of these results together with UV-vis optical absorption, IR spectra, and thermoluminescence studies have indicated a gradual increase in the concentration of mono-valent copper ions due to γ-ray treatment of the glass network. The additional studies have confirmed that these Cu+ ions occupy network-forming positions, increase the polymerization of the borophosphate glass network, and facilitates for the increase of insulating strength of the titled glass. © 2016 Springer-Verlag Berlin Heidelberg Source


Veeraiah N.,Acharya Nagarjuna University | Gandhi Y.,Kakani Venkata Ratnam College | Kadam R.M.,Bhabha Atomic Research Center | Swamy B.J.R.,Acharya Nagarjuna University | And 3 more authors.
Materials Letters | Year: 2016

CaF2-P2O5-B2O3 glasses mixed with 0.2 mol% of MnO were prepared. The prepared samples were exposed to γ-rays for dose rate of 1.5 kGy/h for two hours and their EPR spectra were recorded in the temperature range 300-475 K. The spectra of pure as well as MnO doped glass samples exhibited a new and nearly axially symmetric (g||=2.0085 and g||=2.0090, A||= 34 G and A||= 52 G) signal with doublet hyperfine structure. The signal is attributed to PO42- radical formed by trapped hole on non-bonding orbital of oxygen. The analysis of these data together with thermoluminescence (TL) studies indicated that PO42- radical plays a crucial role in TL emission. © 2015 Elsevier B.V. All rights reserved. Source

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