Browsing by Subject "Fused salts"

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    Microstructural and Radioluminescence Characteristics of Nd3+ Doped Columbite-Type SrNb2O6 Phosphor
    (Springer New York LLC, 2017) Ekmekçi M.K.; İlhan M.; Ege A.; Ayvacıklı M.
    Undoped and different concentration Nd3+ doped SrNb2O6 powders with columbite structure were synthesized by molten salt process using a mixture of strontium nitrate and niobium (V) oxide and NaCl-KCl salt mixture as a flux under relatively low calcining temperature. X-ray diffraction analysis results indicated that SrNb2O6 phases found to be orthorhombic columbite single phase for undoped, 0.5 and 3 mol% Nd3+ doping concentrations. Phase composition of the powders was examined by SEM-EDS analyses. Radioluminescence properties of Nd3+ doped samples from UV to near-IR spectral region were studied. The emissions increased with the doping concentration of up to 3 mol%, and then decreased due to concentration quenching effect. There is a sharp emission peak around 880 nm associated with 4F5/2 → 4I9/2 transition in the Nd3+ ion between 300 and 1100 nm. The broad emission band intensity was observed from 400 to 650 nm where the peak intensities increased by increasing Nd3+ doping concentration. All the measurements were taken under the room temperature. © 2017, Springer Science+Business Media New York.
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    Judd-Ofelt parameters and X-ray irradiation results of MNb2O6:Eu3+(M = Sr, Cd, Ni) phosphors synthesizedviaa molten salt method
    (Royal Society of Chemistry, 2021) İlhan M.; Ekmekçi M.K.; Keskin İ.Ç.
    Trivalent Eu-activated MNb2O6(M = Sr, Cd, Ni) ceramic phosphors were produced using the molten salt route, which involves a low sintering temperature and provides improved homogeneity. The photoluminescence (PL) and radioluminescence (RL) spectra of phosphors exhibited characteristic Eu3+emissions with5F0→7Fjtransitions, and strong peaks occurred at the5D0→7F2transition. The PL and RL emissions of SrNb2O6:Eu3+decreased over 3 mol%, while both emissions for CdNb2O6:Eu3+and NiNb2O6:Eu3+increased with increasing Eu3+concentration. The spectral properties of phosphors were evaluated by determining Judd-Ofelt intensity parameters (Ω2,Ω4) from the PL emission spectrum. The quantum efficiencies (ηQE%) of MNb2O6:Eu3+(M = Sr, Cd, Ni) phosphors with the highest emission were found as 61.87%, 41.89%, and 11.87% respectively. Bandwidths (σe× Δλeff) and optical gains (σe×τ) of MNb2O6:Eu3+(M = Sr, Cd, Ni) phosphors with highest emissions were found as follows; 24.182 × 10−28, 28.674 × 10−28, 38.647 × 10−28cm3and 20.441 × 10−25, 13.790 × 10−25, 3.987 × 10−25cm2s, respectively, corresponding to the5D0→7F2transition. © The Royal Society of Chemistry 2021.
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    Effect of boron incorporation on the structural, morphological, and spectral properties of CdNb2O6:Dy3+ phosphor synthesized by molten salt process
    (Elsevier Ltd, 2023) İlhan M.; Ekmekçi M.K.; Güleryüz L.F.
    The effect of boron addition on the structural, morphologic and spectral properties was investigated by using xDy3+ (x = 0.5, 3, 6 mol%) doped, and xDy3+, yB3+ (y = 0, 5, 15, 25 mol%) co-doped CdNb2O6 powders produced by molten salt method. X-ray diffractions (XRD) of all Dy3+ doped, and B3+, Dy3+ co-doped samples showed that they retained the single-phase structure. The homogeneous dissolution of the Dy3+ doping without forming an impurity phase in the structure can be attributed to the flux effect of the molten salt process and boron doping. Scanning electron microscopy (SEM) micrographs of the B3+, Dy3+ co-doped grains showed that the effect of boron promotes grain growth and prismatic-like grain shape. Photoluminescence (PL) emissions of the phosphors with the excitation of 351.9 nm were monitored by the 4F9/2→6H15/2, 4F9/2→6H13/2, and 4F9/2→6H11/2 transitions. PL excitations and a broad peak at 275 nm originating from the O2–→Nb5+ band transition were observed with the emission of 577.9 nm. The PL emissions of Dy3+, B3+ co-doped phosphors increased about two fold compared to Dy3+ doped samples. The increase in PL may be related to the increased presence of luminescence centers at or near grain surface due to the decreasing surface area (SA)/volume (V) ratio as the growth of B3+ co-doped grains and the transformation from rod-like to prismatic-like shape. The increased Dy3+ presence led to a decrease in observed lifetime, while the B3+ increase did not cause any change. The study may provide a different perspective for the understanding and controlling of grain morphology and the luminescence relation for RE-doped phosphors. © 2023 Elsevier B.V.