• S V Godbole

      Articles written in Bulletin of Materials Science

    • Thermally stimulated luminescence and photoluminescence investigations of Eu3+ and Eu2+ doped SrBPO5

      Mithlesh Kumar T K Seshagiri S V Godbole

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      Thermally stimulated luminescence (TSL) investigations of SrBPO5:Eu3+ and SrBPO5:Eu2+ phosphors were carried out in the temperature range of 300–650 K. In order to characterize the phosphors, X-ray diffraction and photoluminescence (PL) techniques were used. The emission spectrum of air heated SrBPO5:Eu3+ phosphor exhibited emission bands at 590, 614, 651 and 702 nm under 248 nm excitation, assigned to transitions of Eu3+ ion. In phosphor prepared in reducing (Ar + 8% H2) atmosphere, a broad emission band due to Eu2+ ranging from 350 to 400 nm was observed with 340 nm excitation. EPR studies have confirmed the presence of Eu2+ ions in the samples prepared in reducing atmosphere. TSL glow curve of SrBPO5:Eu3+ had shown intense peaks around 397, 510, 547 K and a weak peak around 440 K whereas in case of SrBPO5:Eu2+ system, glow peaks at 414, 478 and weak peak at 516 nm were observed. The shift in TSL glow pattern can be attributed to stabilization of different oxidation states of the dopant ion in the host lattice. Apart from this, TSL trap parameters such as trap depth and frequency factor were determined. Spectral characteristics of TSL emission have shown that Eu3+/Eu2+ ion acts as the luminescent centre in the respective phosphors.

    • Photoluminescence, thermally stimulated luminescence and electron paramagnetic resonance studies of U6+ doped BaSO4

      M K Bhide T K Seshagiri Sashikala Ojha S V Godbole

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      U6+ doped BaSO4 samples were synthesized by precipitation route. PL, TL and EPR investigations of 𝛾 and self 𝛼 irradiated samples were carried out. PL spectra of these samples give structured broad band peaking around 518 nm with five vibronic bands centred around 498.4, 516.0, 533.7, 554.0 and 575.1 nm, respectively and the average frequency of symmetric stretching of O=U=O in the ground electronic state was found to be 674 cm−1. Trap level spectroscopic studies of U doped BaSO4 give glow peaks at 411, 488 and 512 K, respectively and their spectral characteristics are typical of UO$_{2}^{2+}$ emission. EPR studies of 𝛾-irradiated U6+:BaSO4 sample have shown the presence of sulphoxy centred radicals like SO$_{4}^{−}$ and SO$_{3}^{−}$ in addition to OH$^{\bullet}$, O$_{3}^{−}$ and SH2−. TSL peaks at 411 and 488 K were correlated with thermal destruction of SO$_{4}^{−}$ and SO$_{3}^{−}$ radicals.

    • Synthesis, characterization, photoluminescence and thermally stimulated luminescence investigations of orange red-emitting Sm3+-doped ZnAl2O4 phosphor

      Mithlesh Kumar V Natarajan S V Godbole

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      Sm3+-doped ZnAl2O4 phosphor was synthesized by citrate sol–gel method and characterized using X-ray diffraction and scanning electron microscopy to identify the crystalline phase and determine the particle size. Photoluminescence (PL) studies on the sample showed emission peaks at 563, 601, 646 and 707 nm with 𝜆ex = 230 nm corresponding to the ${}^{4}G_{5/2} \rightarrow {}^{6}H_{5/2}, {}^{4}G_{5/2} \rightarrow {}^{6}H_{7/2}, {}^{4}G_{5/2} \rightarrow {}^{6}H_{9/2}$ and ${}^{4}G_{5/2} \rightarrow {}^{6}H_{11/2}$ transitions, respectively, due to Sm3+ ions. PL lifetime decay studies confirmed that Sm3+ ions partly entered into the lattice by replacing Al3+ ions and remaining located at the surface of ZnAl2O4 host matrix. Thermally stimulated luminescence (TSL) studies of 𝛾-irradiated Sm3+-doped ZnAl2O4 sample showed two glow peaks at 440 and 495 K, the former being most intense than the latter. The trap parameters were determined using different heating rate methods. Spectral characteristics of the TSL glow showed emission around 565, 599 and 641 nm, indicating the role of Sm3+ ion as the luminescent centre. A probable mechanism for the prominent TSL glow peak, observed at 440 K, was proposed. CIE chromaticity coordinates for the system was evaluated, which suggested that Sm3+-doped ZnAl2O4 could be employed as a potential orange red-emitting phosphor.

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      Posted on October 12, 2020

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      Chemical Sciences 2020

      Prof. Surajit Dhara — School of Physics, University of Hyderabad, Hyderabad
      Physical Sciences 2020

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