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Luminescence properties in relation to controllable morphologies of Ba <sub/>3</sub> [Ge <sub/>2</sub> B <sub/>7</sub> O <sub/>16</sub> (OH) <sub/>2</sub> ](OH)(H <sub/>2</sub> O):Eu <sup>3+</sup> and its thermal conversion product Ba <sub/>3</sub> Ge <sub/>2</sub> B <sub/>6</sub> O <sub/>16</sub> :Eu <sup>3+</sup>
摘要： Luminescence properties in relation to controllable morphologies of Ba3[Ge2B7O16(OH)2](OH)(H2O):Eu3+ and its thermal conversion product Ba3Ge2B6O16:Eu3+ were investigated. Three types of morphologies of Eu3+-doped Ba3[Ge2B7O16(OH)2](OH)(H2O) phosphors were obtained via hydrothermal reactions by different kinds of raw materials. In addition, Ba3Ge2B6O16:Eu3+ phosphors were obtained by calcining the precursor Ba3[Ge2B7O16(OH)2](OH)(H2O):Eu3+. The structure and morphology of the obtained samples were characterized by XRD, EDS, FT-IR, TG-DTA, SEM and HRTEM. Herein, the effects of the synthesis parameters, including the reaction temperature, boron sources and the dosage, doping of rare earth on the photoluminescence (PL) properties of Ba3[Ge2B7O16(OH)2](OH)(H2O) were investigated in detail. The lifetime and absolute quantum yield (QY) of different morphologies of Ba3[Ge2B7O16(OH)2](OH)(H2O):Eu3+ were also measured. The PL properties of the Ba3Ge2B6O16:Eu3+ phosphor prepared by the precursor calcination method compared with those prepared by the high-temperature solid-state method are discussed.
关键词： Morphologies,Eu3+ doping,Hydrothermal,Borogermanates,Phosphors,Luminescence
更新于2025-11-14 17:04:02
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The Bond-Energy Method in Site Occupancy and Property of High Concentration Eu <sup>3+</sup> in Sr <sub/>2</sub> CeO <sub/>4</sub> Phosphors
摘要： The low concentration of Eu3+ doped Sr2CeO4 phosphors has been widely studied in recent years and in this paper, we researched the properties of high concentration Eu3+ doped in Sr2CeO4. The Sr2Ce(1?x)Eu4?x/2 (x = 0, 1%, 10%, 20%) phosphors were obtained by traditional solid-state reaction. Photoluminescence (PL) spectra are characterized the property of samples. PL spectra illustrate that the concentration of Eu3+ increased, the intensity of 5D0-7F1, 5D0-7F2 increased and intensity of Sr2CeO4 host emission intensity was decreased. The phenomenon can be ascribed to the energy transfer from Ce4+ to Eu3+. When the concentration of Eu3+ is 20%, the completely red emission can be obtained even if no other ions are doped under the excitation wavelength of 350 nm, it is proved that Eu3+ occupied Ce sites rather than Sr site in Sr2CeO4 samples. The conclusion we make is due to the value of ΔE Eu-Ce-O and ΔE Eu-Sr-O calculated by bond-energy method, the smaller the value, the easier it is for the doped ions Eu3+ to enter the site.
关键词： Site Occupancy Preference,High Concentration,Eu3+ Doping,Bond-Energy Method,Sr2CeO4
更新于2025-09-19 17:15:36
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Elucidating the structure and optimising the photoluminescence properties of Sr2Al3O6F: Eu3+ oxyfluorides for cool white-LEDs
摘要： Herein, Sr2Al3O6F in hexagonal symmetry was synthesized via a solid-state methodology. The X-ray diffraction pattern of Sr2Al3O6F was refined by the Rietveld refinement with lattice parameters a = 17.8232(1) ? and c = 7.2168(0) ?. The stability of the crystal structure is further confirmed from the results of bond valence sums and the global instability index. The theoretical calculations of the electronic and optical behaviors of the Sr2Al3O6F were analyzed by density functional theory and the obtained results of the lattice parameters and direct bandgap were found close to the experimental data. The chemical states and elemental composition of Sr2Al3O6F were also authenticated by X-ray photoelectron spectroscopy (XPS). To evaluate the suitability of the Sr2Al3O6F structure as high efficient red phosphor, a series of Eu3+ doped Sr2-xEuxAl3O6F (x = 0.0 to 0.10) were synthesized, which showed intense red-orange emission (5D0→7F1,2) at UV and blue excitations. The photoluminescence intensity corresponding to 5D0→7F2 transition decreased significantly for x = 0.10 due to the luminescence quenching. Nevertheless, further enhancement in photoluminescence of Sr1.9Al3O6F: Eu0.1 sample was realized with the substitution of 0.1 mol Ba2+ ion for 0.1 mol Sr2+ ion. The various radiative properties of the emission bands were also analyzed through the Judd-Ofelt theory. The optimized Sr1.8Al3O6F: Ba0.1/Eu0.1 phosphor showed high red color purity (> 95%), and moderate thermal stability of around 72% at 150 oC, suggesting that it could be an ideal red component for white-LEDs. A white-LED comprising the commercial yellow phosphor and the optimized sample showed bright white light having the CRI of 80.5%, CCT of 5510 K, and CIE of (0.33, 0.36) indicating that Sr1.8Al3O6F: Ba0.1/Eu0.1 phosphor is an appropriate red component for cool white-LEDs.
关键词： Eu3+-doping,Rietveld refinement,Hexagonal Sr2Al3O6F,density functional theory,white-LEDs,red phosphors
更新于2025-09-19 17:13:59
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Photoluminescence features of new Eu <sup>3+</sup> -doped Gd <sub/>4</sub> Mo <sub/>7</sub> O <sub/>27</sub> phosphors synthesized using glass crystallization technique
摘要： New Eu3+-doped Gd4Mo7O27 crystals (the molar ratio of Gd2O3/MoO3 = 1/3.5) with a monoclinic structure C2/c (an inversion symmetry) were synthesized through the crystallization of xEu2O3-(18.89-x)Gd2O3-66.11MoO3-15B2O3-1Al2O3 glasses (x = 0.0472 and 1.889) and photoluminescence (PL) emissions of Eu3+ ions were measured for the first time. The crystallized glass with no Eu2O3 addition (x = 0) showed a blue color under the irradiation of ultra-violet light with a wavelength of λ = 254 nm, the emitting color of the crystallized glass with x = 0.0472 was pink, and that of the crystallized glass with x = 1.889 was orange. The charge transfer (CT) of O2-→Mo6+ providing broad peaks centered at around 325 nm was observed in the crystallized glasses. The peak intensity at 591 nm for the 5D0→7F1 transition of Eu3+ ions in the crystallized glasses with x = 0.0472 and 1.889 was very close to that at 615 nm for the 5D0→7F2 transition for the excitation of λex = 394.5 nm. We propose potential of Gd4Mo7O27 as a new host crystal for rare-earth-doped phosphors.
关键词： Eu3+-doping,Glass crystallization,Photoluminescence,Phosphor,Gd4Mo7O27
更新于2025-09-04 15:30:14