White emitting phosphors based on glasses of the type 10AlF3–10TiO2–39PbO–30H3BO3–10SiO2–xEu2O3–(1−x)Tb2O3: An energy transfer study (original) (raw)
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White light emission of dysprosium doped lanthanum calcium phosphate oxide and oxyfluoride glasses
Optical Materials, 2017
Lanthanum calcium phosphate oxide and oxyfluoride glasses doped with dysprosium oxide were prepared by melt-quenching technique with chemical composition 20La 2 O 3 :10CaO:69P 2 O 5 :1Dy 2 O 3 and 20La 2 O 3 :10CaF 2 :69P 2 O 5 :1Dy 2 O 3. The physical, optical and luminescence properties of the glass samples were studied to evaluate their potential to using as luminescence materials for solid-state lighting applications. The density, molar volume and refractive index of the glass samples were carried out. The optical and luminescence properties were studied by investigating absorption, excitation, and emission spectra of the glass samples. The absorption spectra were investigated in the UVeVis eNIR region from 300 to 2000 nm. The excitation spectra observed under 574 nm emission wavelength showed the highest peak centered at 349 nm (6 H 15/2 / 6 P 7/2). The emission spectra, excited with 349 nm excitation wavelength showed two major peaks corresponding to 482 nm blue emission (4 F 9/ 2 / 6 H 15/2) and 574 nm yellow emission (4 F 9/2 / 6 H 13/2). The experimental lifetime were found to be 0.539 and 0.540 for oxide and oxyfluoride glass sample, respectively. The x,y color coordinates under 349 nm excitation wavelength were (0.38, 0.43) for both glass samples, that be plotted in white region of CIE 1931 chromaticity diagram. The CCT values obtained from the glass samples are 4204 K for oxide glass and 4228 K for oxyfluoride glass corresponding to the commercial cool white light (3100 e4500 K). Judd-Ofelt theory had also been employed to obtain the J-O parameters (U 2 , U 4 and U 6), oscillator strength, radiative transition possibility, stimulated emission cross section and branching ratio. The U 2 > U 4 > U 6 trend of J-O parameters of both glass samples may indicate the good quality of a glass host for using as optical device application. Temperature dependence of emission spectra was studied from 300 K to 10 K and found that the intensity of the emission peak was found to be increased with decreasing of the temperature. The results of the investigations in this work confirmed that the present Dy-doped lanthanum calcium phosphate oxide and oxyfluoride glasses perform high potential for using as efficient luminescence materials for solid-state lighting applications, especially for white LEDs. Furthermore, the oxyfluoride glass sample provides more luminescence potential than the oxide glass sample.
Optical Materials, 2014
Heavy metal oxide glass of the type GeO 2 -PbO-Bi 2 O 3 was applied as a matrix for luminescent materials co-doped with Tb 3+ and Eu 3+ ions of different molar ratio. The undoped glass matrix with the composition 80GeO 2 -19PbO-1Bi 2 O 3 was characterized by XRD and DSC techniques. Its structure was studied by FTIR spectroscopy. The FTIR spectra suggested that GeO 4 , GeO 6 , BiO 3 , BiO 6 , PbO 3 and PbO 4 structural units are present in the glass. In the case of the 79GeO 2 -19PbO-Bi 2 O 3 -xEu 2 O 3 -(1 À x)Tb 2 O 3 luminescent glasses, reflection, luminescence and excitation spectra were recorded as well as time resolved luminescence technique was used. Two luminescence effects were analyzed, viz. cross relaxation and Tb 3+ ? Eu 3+ energy transfer.
Elaboration and Luminescent Properties of Eu/Tb Co-Doped GdPO4-Based Glass Ceramics for White LEDs
Journal of the American Ceramic Society, 2012
Eu/Tb single-doped and co-doped oxyfluoride aluminosilicate glasses and glass ceramics containing GdPO 4 nanocrystals were elaborated, and their structural and luminescent properties were investigated by X-ray diffraction, Transmission electron microscopy, excitation and emission spectra, as well as decay lifetime measurement. Excited by 350 nm light, a combination of blue (5d?4f of Eu 2+ ), green ( 5 D 4 ? 7 F 5 of Tb 3+ ) and red ( 5 D 0 ? 7 F 2 of Eu 3+ ) emissions emerges to achieve white emission in Eu/Tb co-doped precursor glasses and glass ceramics. Our research shows that Eu/Tb co-doped precursor glasses and GdPO 4 -based glass ceramics may be applied in lighting and luminescent aspects.
Progress in optical science and photonics, 2023
The investigation on single phase multi-color phosphors is highly meaningful for near-ultraviolet chip based white light emitting diodes. In this work, a series of Eu 2+ and Tb 3+ singly doped and Eu 2+ /Tb 3+ codoped Sr 5 (PO 4) 3 Cl phosphors were synthesized via a high-temperature solid state reaction method. The luminescence spectra and decay curves of Eu 2+ and Tb 3+ singly doped samples were discussed, the optimal doping concentrations were determined. Thanks to the spectra overlap between Eu 2+ and Tb 3+ , nonradiative energy transfer from Eu 2+ to Tb 3+ was investigated. It is found electric dipole-dipole interaction played the main role for the energy transfer in codoped samples, the highest energy transfer efficiency was calculated to be 60.98%. Tunable emissions are observed for codoped samples by adjusting doping concentration. The thermal quenching properties were discussed and the activation energy (E) was estimated in the present work.
Eu-, Tb-, and Dy-Doped Oxyfluoride Silicate Glasses for LED Applications
Luminescence glass is a potential candidate for the light-emitting diodes (LEDs) applications. Here, we study the structural and optical properties of the Eu-, Tb-, and Dy-doped oxyfluoride sili-cate glasses for LEDs by means of X-ray diffraction, photolumi-nescence spectra, Commission Internationale de L'Eclairage (CIE) chromaticity coordinates, and correlated color temperatures (CCTs). The results show that the white light emission can be achieved in Eu/Tb/Dy codoped oxyfluoride silicate glasses under excitation by near-ultraviolet light due to the simultaneous generation of blue, green, yellow, and red-light wavelengths from Tb, Dy, and Eu ions. The optical performances can be tuned by varying the glass composition and excitation wavelength. Furthermore , we observed a remarkable emission spectral change for the Tb 3+ single-doped oxyfluoride silicate glasses. The 5 D 3 emission of Tb 3+ can be suppressed by introducing B 2 O 3 into the glass. The conversion of Eu 3+ to Eu 2+ takes place in Eu single doped oxyfluoride aluminosilicate glasses. The creation of CaF 2 crystals enhances the conversion efficiency. In addition, energy transfers from Dy 3+ to Tb 3+ and Tb 3+ to Eu 3+ ions occurred in Eu/Tb/Dy codoped glasses, which can be confirmed by analyzing fluorescence spectra and energy level diagrams.
Journal of Luminescence, 2021
Augmenting the photoluminescence (PL) properties of Samarium (Sm 3+) doped Zinc Strontium fluoroborosilicate glass (ZSFBSi glass) by varying the Sm 3+ ions concentration unlocks new prospects for their application as luminescent devices. This paper presents absorption, photoluminescence (PL), energy transfer and color chromaticity parameterization of ZSFBSi glass doped with Sm 3+ ions concentrations. The Judd-Ofelt (J-O) theory in correlation with absorption as well as PL spectra leads to the estimation of radiative parameters of the excited luminescent states of Sm 3+ ions needed to understand the luminescent potentiality of the as-prepared glasses. The absorption spectral data reveals the nature of bonding between Sm 3+ ions and oxygen ligands in the as-quenched glasses as ionic and the result is consistent with the J-O analysis. The PL spectra of as-quenched glasses exhibit greenish-yellow, orange-red, light red and red color ascribed to 4 G 5/2 → 6 H 5/2 , 6 H 7/2 , 6 H 9/2 , 6 H 11/2 emission bands at 563, 599, 646 and 706 nm, respectively. The PL intensity enhances with an escalation in Sm 3+ ions content until 1.0 mol% and reduces thereafter, owing to a proficient energy transfer (ET) process. The Dexter theory and Inokuti-Hirayama (I-H) model identified the foremost ET process associated with the asquenched glasses as dipole-dipole in nature. The CIE color coordinates (x, y) and Correlated Color Temperature (CCT) were calculated to cognize the effectiveness of as-quenched glasses in radiative cool white emission. The estimated branching ratios, emission cross-sections, gain bandwidth, quantum efficiency, optical gain, color coordinates and CCT finally reveals that the as-quenched glasses can be used in luminescent devices and amide all, 1.0 mol% Sm 2 O 3 in ZSFBSi glass is highly appropriate for white LEDs as well as orange-red luminescent devices.
Journal of Molecular Structure, 2019
Glasses of the composition 30BaO-2Ga 2 O 3-(27.8-x) B 2 O 3-40SiO 2-xCe 2 O 3-0.2Tb 2 O 3 (0 x 1.0) were synthesized by conventional melting and quenching process. The samples were characterized by XRD, EDS, TG-DTA, FT-IR and Raman studies. Optical absorption (OA) and photoluminescence (PL) spectral studies were performed. X-ray diffraction patterns of samples have clearly confirmed the amorphous nature of the samples. Differential thermal analysis indicated thermal stability of glasses. Raman and FTIR spectra have exhibited different fundamental vibrational bands of borate and silicate structural units. The absorption spectra exhibited four absorption bands of Tb 3þ ions from the ground state 7 F 6 in the visible and NIR regions. In addition, a feeble band corresponding to 4f (2 F J) / 5d (2 A 1g) absorption transition of Ce 3þ ions at 416 nm is also located in these spectra. Optical bandgap (E g) evaluated using Tauc plots, is observed to decrease with increase of Ce 2 O 3 up to 0.6 mol%. Luminescence spectra (recorded at l exc ¼ 329 nm) of glass co-doped with 0.6 mol% CTb exhibited the maximal PL output. The non-exponential time decay profiles are finely fitted to Inokuti-Hirayama (I-H) model for S ¼ 6. This observation suggests that the energy transfer mechanism between Ce 3þ / Tb 3þ is connected with the dipole-dipole interaction. The CIE coordinates of 0.6CTb glass are estimated to be (0.257, 0.307). These values are found to be nearer to the standard values of ideal white light and hence it is concluded that the glass of this composition is useful for white LEDs.
Journal of Luminescence, 2015
The radiative properties of Dy-doped glasses and glass-ceramic phosphors with varying lead and cadmium fluoride content are investigated in the present study for white light emitting applications. The precipitation of cubic lead fluoride phase of 10-18 nm crystallites was determined with the help of x-ray diffraction studies and the nanocrystalline nature was confirmed with scanning electron microscopy studies. The small size of the nanocrystallites enables the fabrication of transparent glass-ceramics which is verified by UV-VIS spectroscopic study. The photoluminescence and lifetime measurements indicate towards progressive changes in the Dy 3+ ion surroundings and propose enhanced energy transfers taking place post heat treatments. Finally, CIE chromaticity coordinates are found to lie in the white region proposing the suitability of the present studied materials for color display devices.
Journal of Non-crystalline Solids, 2023
Lithium Lead Alumino Borate (LiPbAlB) glasses doped with Dy 3+ ions with varying concentration were synthesized by using the melt quenching technique to understand their feasibility in solid state lighting and laser devices. From the absorption spectra, bonding parameters () were evaluated to understand the nature of bonding between Dy 3+ ions and its surrounding ligands. Judd-Ofelt intensity parameters estimated from the experimental oscillator strengths were used to evaluate various radiative parameters for the fluorescent levels of Dy 3+ ions. From the decay curves, the experimental lifetimes were measured and coupled with the radiative lifetimes to evaluate the quantum efficiency. The decay profile changes from exponential to non-exponential with increase in Dy 3+ ion concentration resulting decrease in experimental lifetimes. Inokuti-Hirayama model applied to the decay spectral profiles confirm dipole-dipole interaction responsible for their conversion from exponential to non-exponential. By exciting the glasses with different n-UV radiations, the CIE chromaticity coordinates and correlated color temperatures (CCT) were calculated to understand the utility of as-prepared glasses in cool white light generation. From the evaluated radiative parameters, CIE coordinates, CCT temperatures, emission cross-sections, quantum efficiency and confocal images, it was observed that LiPbAlB glass with 0.5 mol% Dy 3+ ions are more suitable for the development of w-LEDs and Lasers.