• T K Seshagiri

      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.

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