Abstract:Nanocrystalline transparent BaF2:Eu3+ glass-ceramic materials emitting reddish-orange light were fabricated using a low-temperature sol-gel method. Several experimental techniques were used to verify structural transformation from precursor xerogels to sol-gel glass-ceramic materials containing fluoride nanocrystals. Thermal degradation of xerogels was analyzed by thermogravimetric analysis (TG) and differential scanning calorimetry method (DSC). The presence of BaF2 nanocrystals dispersed in sol-gel materials… Show more
“…This originates from the fact that Eu 3+ can occupy four lattice sites with each giving lines at slightly different wavelengths due to the different crystal field generated. This is the opposite to phosphors where only one lattice site is available for Eu 3+ ions and there are very few excitation lines which, in turn, are also very narrow [13,[26][27][28][29]. The absorption strength of the synthesized phosphors increased with increasing Eu 3+ concentration.…”
Solid state white light sources based on a near-UV LED chip are gaining more and more attention. This is due to the increasing efficiency of near-UV-emitting LED chips and wider phosphors selection if compared to devices based on blue LED chips. Here, a brief overview is given of the concepts of generating white light employing near-UV LED and some optical properties of the available phosphors are discussed. Finally, the synthesis and optical properties of very efficient red-emitting Ba2Y5B5O17:Eu3+ phosphor powder and ceramics is reported and discussed in terms of possible application as a red component in near-UV LED-based white light sources.
“…This originates from the fact that Eu 3+ can occupy four lattice sites with each giving lines at slightly different wavelengths due to the different crystal field generated. This is the opposite to phosphors where only one lattice site is available for Eu 3+ ions and there are very few excitation lines which, in turn, are also very narrow [13,[26][27][28][29]. The absorption strength of the synthesized phosphors increased with increasing Eu 3+ concentration.…”
Solid state white light sources based on a near-UV LED chip are gaining more and more attention. This is due to the increasing efficiency of near-UV-emitting LED chips and wider phosphors selection if compared to devices based on blue LED chips. Here, a brief overview is given of the concepts of generating white light employing near-UV LED and some optical properties of the available phosphors are discussed. Finally, the synthesis and optical properties of very efficient red-emitting Ba2Y5B5O17:Eu3+ phosphor powder and ceramics is reported and discussed in terms of possible application as a red component in near-UV LED-based white light sources.
“…Therefore, such materials could be successfully predisposed for use in laser technologies [ 38 ], bio-imaging [ 39 ], or to increase the efficiency of solar cells [ 40 ]. Moreover, according to our previous results for sol-gel nano-glass-ceramics containing divalent metals fluorides, MF 2 (M = Ca, Sr, Ba), singly-doped with Eu 3+ ions, the most efficient segregation of Eu 3+ inside fluoride crystal lattice, was reported for the SiO 2 -CaF 2 system [ 41 , 42 , 43 ]. Indeed, a clear correlation was observed between the average decay time of the 5 D 0 state and growing difference in ionic radius of Eu 3+ and each of individual M 2+ cation in the following order: Ca 2+ → Sr 2+ → Ba 2+ (SiO 2 -CaF 2 :Eu 3+ : τ avg = 11.92; SiO 2 -SrF 2 :Eu 3+ : τ avg = 7.77; SiO 2 -BaF 2 :Eu 3+ : τ avg = 4.08 ms).…”
In this work, the series of Tb3+/Eu3+ co-doped xerogels and derivative glass-ceramics containing CaF2 nanocrystals were prepared and characterized. The in situ formation of fluoride crystals was verified by an X-ray diffraction technique (XRD) and transmission electron microscopy (TEM). The studies of the Tb3+/Eu3+ energy transfer (ET) process were performed based on excitation and emission spectra along with luminescence decay analysis. According to emission spectra recorded under near-ultraviolet (NUV) excitation (351 nm, 7F6 → 5L9 transition of Tb3+), the mutual coexistence of the 5D4 → 7FJ (J = 6–3) (Tb3+) and the 5D0 → 7FJ (J = 0–4) (Eu3+) luminescence bands was clearly observed. The co-doping also resulted in gradual shortening of a lifetime from the 5D4 state of Tb3+ ions, and the ET efficiencies were varied from ηET = 11.9% (Tb3+:Eu3+ = 1:0.5) to ηET = 22.9% (Tb3+:Eu3+ = 1:2) for xerogels, and from ηET = 25.7% (Tb3+:Eu3+ = 1:0.5) up to ηET = 67.4% (Tb3+:Eu3+ = 1:2) for glass-ceramics. Performed decay analysis from the 5D0 (Eu3+) and the 5D4 (Tb3+) state revealed a correlation with the change in Tb3+–Eu3+ and Eu3+–Eu3+ interionic distances resulting from both the variable Tb3+:Eu3+ molar ratio and their partial segregation in CaF2 nanophase.
“…The xerogels singly doped with Tb 3+ and co-activated with Tb 3+ , Eu 3+ ions were prepared via the previously described sol-gel synthesis [22]. The reagents from Sigma-Aldrich (St. Louis, MO, USA) were applied for the fabrication the samples.…”
Section: Methodsmentioning
confidence: 99%
“…Our previously published work [22] was concerned with sol-gel SiO 2 -BaF 2 nanoglass-ceramic systems doped with europium ions in a trivalent oxidation state. Their structural and optical properties have been studied using various experimental techniques, such as differential scanning calorimetry (DSC), X-ray diffraction (XRD), transmission electron microscopy (TEM) coupled with the energy-dispersive X-ray spectroscopy (EDS), infrared (ATR-IR), and luminescence spectroscopy.…”
The synthesis and characterization of multicolor light-emitting nanomaterials based on rare earths (RE3+) are of great importance due to their possible use in optoelectronic devices, such as LEDs or displays. In the present work, oxyfluoride glass-ceramics containing BaF2 nanocrystals co-doped with Tb3+, Eu3+ ions were fabricated from amorphous xerogels at 350 °C. The analysis of the thermal behavior of fabricated xerogels was performed using TG/DSC measurements (thermogravimetry (TG), differential scanning calorimetry (DSC)). The crystallization of BaF2 phase at the nanoscale was confirmed by X-ray diffraction (XRD) measurements and transmission electron microscopy (TEM), and the changes in silicate sol–gel host were determined by attenuated total reflectance infrared (ATR-IR) spectroscopy. The luminescent characterization of prepared sol–gel materials was carried out by excitation and emission spectra along with decay analysis from the 5D4 level of Tb3+. As a result, the visible light according to the electronic transitions of Tb3+ (5D4 → 7FJ (J = 6–3)) and Eu3+ (5D0 → 7FJ (J = 0–4)) was recorded. It was also observed that co-doping with Eu3+ caused the shortening in decay times of the 5D4 state from 1.11 ms to 0.88 ms (for xerogels) and from 6.56 ms to 4.06 ms (for glass-ceramics). Thus, based on lifetime values, the Tb3+/Eu3+ energy transfer (ET) efficiencies were estimated to be almost 21% for xerogels and 38% for nano-glass-ceramics. Therefore, such materials could be successfully predisposed for laser technologies, spectral converters, and three-dimensional displays.
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