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    Enhancement of luminescence and thermal stability in Eu3+-doped K3Y (BO2)6 with Li+ and Na+ co-doping
    (Elsevier, 2024) Kaynar, U. H.; Aydin, H.; Altowyan, A. S.; Hakami, J.; Coban, M. B.; Ayvacikli, M.; Karali, E. Ekdal
    Eu3+-doped and Li+/Na+ co-doped K3Y(BO2)6 (KYBO) phosphors were synthesized through a microwave- assisted sol-gel method, and their structural and photoluminescent (PL) characteristics were examined. X-ray diffraction (XRD) and Rietveld refinement confirm effective dopant incorporation and preservation of the crystalline structure. Fourier Transform Infrared (FTIR) spectroscopy indicates the maintenance of the borate structure, confirming the structural integrity of the phosphors upon doping. The addition of Li+ and Na+ co-dopants notably enhances luminescent efficiency and thermal stability, making these phosphors promising candidates for solid-state lighting (SSL) applications. PL analysis reveals strong red emission peaks at 612 nm, attributed to the 5 D o ? 7 F 2 transition of Eu3+ ions. The study indicates that electric dipole-quadrupole interactions are the primary mechanism for energy migration, with a critical distance of approximately 22.68 & Aring;. This mechanism contributes to concentration quenching at higher doping levels. High temperature PL measurements indicated an activation energy of 0.1389 eV for thermal quenching in the Li+ co-doped sample. Additionally, the Na+ co-doped sample exhibited an abnormal thermal stability behavior, with an even higher activation energy of 0.2536 eV. This suggests that Na+ co-doping significantly enhances the thermal resilience of the phosphor, making it more suitable for high-power light-emitting applications that operate under extreme conditions. CIE chromaticity diagrams highlight the potential for optimizing Eu3+ doping levels, combined with Li+ and Na+ co-doping, to improve luminescent performance and thermal stability for advanced SSL applications. (c) 2024 The Society of Powder Technology Japan. Published by Elsevier BV and The Society of Powder Technology Japan. All rights are reserved, including those for text and data mining, AI training, and similar technologies.
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    Enhancement of luminescence and thermal stability in Eu3+-doped K3Y(BO2)6 with Li+ and Na+ co-doping (vol 35, 104695, 2024)
    (Elsevier, 2024) Kaynar, U. H.; Aydin, H.; Altowyan, Abeer S.; Hakami, J.; Coban, M. B.; Ayvacikli, M.; Karali, E. Ekdal
    [No abstract available]
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    Synthesis, characterization and enhanced photoluminescence and temperature dependence of ZrO2:Dy3+phosphors upon incorporation of K plus ions
    (Elsevier Sci Ltd, 2023) Can, N.; Coban, M. B.; Souadi, G.; Kaynar, Umit H.; Ayvacikli, M.; Guinea, J. Garcia; Karali, E. Ekdal
    This study reports the successful synthesis and comprehensive characterization of ZrO2:Dy3+ phosphors with the incorporation of K+ ions. The introduction of Dy3+ and K+ in the ZrO2 lattice as lanthanide activators demonstrates its potential as an efficient host material. The structural integrity of ZrO2 remains unaltered following the doping process. Fourier-transform infrared spectroscopy (FTIR) analysis confirms the presence of Zr-O and O-H stretching, along with H2O bending modes in the phosphor sample. The wide luminescence band seen at 460 nm is attributed to luminescence defects in the ZrO2 induced by oxygen, and the presence of water molecules. Photoluminescence (PL) spectra analysis reveals pronounced emission peaks at 491 and 578 nm, corresponding to 4F9/2 -> 6H15/2 and 4F9/2 -> 6H13/2 transitions, respectively, upon excitation at 349 nm. Optimizing the Dy3+ doping concentration to 0.4 wt% and achieving a critical distance of 31.82 angstrom resulted in efficient energy transfer. Notably, co-doping K+ as a charge compensator significantly enhances the luminescence intensity. Moreover, at lower temperatures, direct excitation of Dy3+ ions through our pump wavelength, coupled with exciton-mediated energy transfer, leads to a remarkable increase in PL intensity. Tailoring the doping concentrations effectively shifts the emission spectrum of the phosphor mixture, aligning with the standard white light illumination co-ordinates (0.333, 0.333). This property positions the material as a promising candidate for applications in white light-emitting diodes (WLEDs) and various high-quality lighting applications. The enhanced photoluminescence and temperature dependence observed in ZrO2:Dy3+ phosphors upon the incorporation of K+ ions pave the way for their potential utilization in advanced luminescent devices.