Yazar "Guinea, J. Garcia" seçeneğine göre listele

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    Cathodoluminescence and photoluminescence properties of Dy doped La2CaB10O19 phosphor
    (Elsevier, 2020) Ayvacıklı, M.; Kaynar, Ümit H.; Karabulut, Y.; Guinea, J. Garcia; Doğan, T.; Can, N.
    In this study, we report a detailed analysis of the photoluminescence (PL) and cathodoluminescence (CL) properties of La2CaB10O19 (LCB) doped with Dy ion. Dy doped LCB materials were successfully synthesized using a sol-gel combustion method. Dy doped LCB has the monoclinic structure with lattice parameters a = 11.02067 angstrom, b = 6.55755 angstrom, c = 9.10541 angstrom and alpha = gamma = 90.00, and 13 = 91.49?. Under the excitation by a low voltage electron beam and pulse laser at 349 nm, the LCB:Dy3+ phosphor produces the characteristic emission bands of Dy3+ due to intra-configuration transitions of F-4(9/2) -> H-6(15/2) (480 nm, blue), F-4(9/2) -> H-6(13/2) (574 nm, yellow), F-4(9/2) -> H-6(11/2) (662 nm, red) and F-4(9/2) -> H-6(9/2) (752 nm, red). The concentration quenching phenomenon was observed in both CL and PL measurements and optimum doping concentration was estimated to be 2%. We suggest that the concentration quenching mechanism of intense yellow emission at 574 nm was attributed to dipole-dipole interaction for both CL and PL.
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    Structural and temperature dependence luminescence characteristics of RE (RE=Eu3+, Dy3+, Sm3+and Tb3+) in the new gadolinium aluminate borate phosphor
    (Elsevier Sci Ltd, 2023) Madkhali, O.; Kaynar, Umit H.; Alajlani, Y.; Coban, M. B.; Guinea, J. Garcia; Ayvacikli, M.; Pierson, J. F.
    GdAl3(BO3)4:Dy3+, Sm3+, Eu3+, and Tb3+ samples were successfully achieved via a sol-gel combustion method. The observed XRD analysis confirms the formation of the desired GAB host, indicating rhombohedral structures that agree well with JPCD card number 72-1985. The FTIR analyses show the detection of B -O stretching and B -O -B bending modes as well as Al -O and Gd -O bonds in the phosphor samples. Energy dispersive spectroscopy (EDS) analysis reveals that Sm, Eu, Dy, and Tb have been successfully doped into GdAl3(BO3)4. The observed broad intrinsic luminescence band can be caused by oxygen-induced luminescence defects in the GAB host with hydrous precursors. The luminescence properties of rare earth ion-doped GdAl3(BO3)4 samples are analysed by photoluminescence spectra, showing their optimal doping concentrations and critical distances of Dy3+, Eu3+, Sm3+ and Tb3+ are 2 wt% -25.8 angstrom, 7 wt% -17 angstrom, 1 wt% -32.59 angstrom, and 7 wt% -17.03 angstrom. Additionally, the energy transfer mechanism for luminescence quenching was determined as dipole-dipole (for Dy3+, Eu3+, and Tb3+) or dipole-quadrupole (for Sm3+) and the cross-relaxation process. GdAl3(BO3)4 samples obtained by doping with different RE3+ ions exhibit intense light emissions with different colors originating from different RE3+ ions under 349 nm excitation. When doped with different concentrations of RE3+ ions, the luminescence properties of the samples changed. The synthesized luminescence materials have potential ap-plications in lighting and display technologies.
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    Structural and thermal insights into the luminescent behavior of Dy3+-Doped BaZrO3 with alkali metal codopants under UV radiation
    (Pergamon-Elsevier Science Ltd, 2025) Arslanlar, Y. Tuncer; Alajlani, Y.; Coban, M. B.; Kaynar, U. H.; Aydin, H.; Orucu, H.; Guinea, J. Garcia
    This study investigates the structural, thermal, and photoluminescent properties of Dy3+-doped BaZrO3 (BZO) perovskites, synthesized via a co-precipitation method, incorporating alkali metal codopants (Li+, Na+, and K+). Xray diffraction (XRD) analysis confirmed the retention of the cubic perovskite phase following doping, with Rietveld refinement further revealing minor lattice distortions due to Dy3+incorporation. The Williamson-Hall (W-H) analysis revealed average crystallite sizes of 53 nm and 66 nm for undoped and 0.01 Dy3+-doped BaZrO3, respectively, with corresponding micro-strain values of 1.79 x 10-3 and 1.81 x 10-3, suggesting lattice distortions due to incorporation of Dy3+. Fourier transform infrared (FTIR) spectroscopy confirmed the cubic perovskite structure and subtle structural modifications upon doping. Notably, the absence of moisture-related peaks highlights the effectiveness of the synthesis process, including rigorous drying and calcination steps that prevented hydrous species. Photoluminescence (PL) analysis of Dy3+-doped BaZrO3 exhibited three prominent emission peaks at 452 nm, 573 nm, and 656 nm under 368 nm excitation. These peaks correspond to the characteristic intra-4f electronic transitions of Dy3+ ions, specifically, 4I13/2 to 6H15/2, 4F9/2 to 6H13/2, and 4F9/2 to 6H11/2, representing blue, yellow, and red emissions, respectively. Photoluminescence decay studies showed multi-exponential behavior, with the average lifetime decreasing from 641 mu s in undoped BZO to 492 mu s in Dy3+- doped samples attributed to enhanced non-radiative recombination pathways. Among the codopants, Li+ demonstrated the most significant improvement in luminescence intensity and thermal stability by mitigating defects and optimizing charge compensation.
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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.