Structural and optical investigations on Dy 3 þ doped lithium tellurofluoroborate glasses for white light applications (original) (raw)
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Improved white light emission in Dy3+ doped LiF–CaO–Bi2O3–B2O3 glasses
Journal of Non-Crystalline Solids, 2018
The effect of substituting LiF on physical, structural, thermal, optical and photoluminescence properties of Dy 3+ doped calcium bismuth borate glasses is reported in the present work. These glasses have been synthesized in the novel compositional range xLiF-(30-x)CaO-20Bi 2 O 3-50B 2 O 3 + 1 mol% of Dy 2 O 3 (x = 0, 2, 5, 7, 10 and 15 mol %, abbreviated as LFx) through convenient melt-quench route. Non-crystalline nature of each composition has been confirmed through X-ray diffraction. Fundamental vibrations of bismuth-borate groups are identified thorough mid-IR absorption spectra. Thermal properties reveal a non-linear trend in glass transition and crystallization temperatures. In order to evaluate optical band gap, analysis of fundamental absorption edge has been done by considering valid Mott's transitions. The compositional trends in optical band gap have supported thermal and infrared absorption results. Evaluation of photoluminescence emission spectra yielded different emission parameters viz. Y/B ratio, color coordinates (x, y) and CCT (correlated color temperature). It has been found that emission of all compositions lie within the white light region and the emission parameters for samples LF2, LF7 and LF10 lie very close to perfect white light (0.333, 0.333). Therefore, these glasses can play the role of useful materials for WLEDs.
A new-fangled series of Dy 3þ ions doped Single and Mixed Alkali Fluoro Tungsten Tellurite Glasses have been prepared by using melt quenching technique and their spectroscopic behaviour was investigated by using XRD, optical absorption, photoluminescence and lifetime measurements. The bonding parameter studies reveal the ionic nature of the DyeO bond in the present glasses. From the absorption spectra, the Judd-Ofelt (J-O) intensity parameters have been determined and in turn used to determine various radiative properties for the different emission transitions from the 4 F 9/2 fluorescent level. The photo-luminescence spectra of all the glasses exhibit two intensified peaks in blue and yellow regions corresponding to the transitions 4 F 9/2 / 6 H 15/2 (483 nm) and 4 F 9/2 / 6 H 13/2 (575 nm) respectively. From the photoluminescence spectra, it is observed that the luminescence intensity is maximum for Dy 3þ ion doped potassium combination of tungsten tellurite glass (TeWK:1Dy). The highest emission cross-section and branching ratio values observed for the 4 F 9/2 / 6 H 15/2 and 4 F 9/2 / 6 H 13/2 transitions suggest the possible laser action in the visible region from these glasses. By correlating the experimental lifetimes (t exp) measured from the decay spectral features with radiative lifetimes (t R), the quantum efficiencies (h) for all the glasses have been evaluated and found to be maximum for potassium combination tungsten tellurite (TeWK:1Dy) glass. The CIE colour chromaticity coordinates (x, y), (u, v), colour correlated temperature (CCT) and Y/B ratio were also estimated from the photoluminescence spectra for different compositions of glasses. The chromaticity colour coordinates evaluated for all the glasses fall within the white light region and white light emission can be tuned by varying the composition of the glass. From all these studies, it was concluded that 1 mol% of Dy 3þ ions doped TeWK glass is more suitable for lasing and white-LED applications.
Concentration dependent luminescence properties of Sm3+-ions in tellurite–tungsten–zirconium glasses
Optical Materials, 2015
Dysprosium (Dy 3?) doped lead free zinc phosphate glasses with chemical compositions (60x) NH 4 H 2 PO 4 ? 20ZnO ? 10BaF 2 ? 10NaF ? xDy 2 O 3 (where x = 0.5, 1.0, 1.5, 2.0 mol%) have been prepared by melt quenching technique. The functional groups of vibrational bands have been assigned and clearly elucidated by FTIR and Raman spectral profiles for all these glass samples. Judd-Ofelt (J-O) intensity parameters (X k : k = 2, 4, 6) have been obtained from spectral intensities of different absorption bands of Dy 3? doped glasses. Radiative properties such as radiative transition probabilities (A R), radiative lifetimes (s R), branching ratios (b R) and integrated absorption crosssections (R) for different excited states are calculated by using J-O parameters. Luminescence spectra exhibit three emission bands (from 4 F 9/2 level to 6 H 15/2 , 6 H 13/2 and 6 H 11/2) for all the concentrations of Dy 3? ions before and after gamma irradiation. Various luminescence properties have been studied by varying the Dy 3? concentration for the three spectral profiles. Fluorescence decay curves of 4 F 9/2 level have been recorded. The energy transfer mechanism that leads to quenching of 4 F 9/2 state lifetime has been discussed by the variation of Dy 3? concentration. These glasses are expected to be useful for yellow luminescent materials.
Spectroscopic properties of Dy3+-doped oxyfluoride glasses for white light emitting diodes
Materials Express, 2013
Dy 3+-doped oxyfluoride (NbFSDy: SiO 2-Nb 2 O 5-K 2 O-ZnF 2-LiF-Dy 2 O 3 glasses were prepared by meltquenching technique and their spectroscopic properties have been investigated. Glass transition and crystallization temperatures have been determined. Phonon energy and vibrational groups of the host matrix have been analyzed from the Raman spectrum. Judd-Ofelt analysis has been carried out to obtain intensity parameters which are used to predict radiative properties for the 1.0 mol% of Dy 2 O 3 doped glass. The characteristic emission parameters such as effective bandwidth and the stimulated emission cross-section have also been intended from the emission spectra for the 4 F 9/2 level of Dy 3+ ions. Sharp emission peaks were observed at 485 nm (blue) of 4 F 9/2 → 6 H 15/2 and 577 nm (yellow) of 4 F 9/2 → 6 H 13/2 transitions under different pump wavelengths. The CIE coordinates for an optimal concentration (0.1 mol% of Dy 2 O 3 were fallen in the white light region for all the pump wavelengths. The correlated color temperature decreases from 5593 K (closer to the day light value of 5500 K) to 5003 K with increase in pump wavelengths. These results indicate that 0.1 mol% Dy 2 O 3-doped glass can be considered for the development of white light emitting diodes.
Indian Journal of Physics, 2019
A new series of Dy 3?-doped alkali fluoroborophosphate glasses were prepared by conventional melt quenching technique, and their structural and optical properties were investigated through XRD, FTIR, optical absorption, luminescence and decay measurements. The X-ray diffraction pattern reveals the amorphous nature of the prepared glasses. The fundamental stretching vibrations of various borate (BO 3 and BO 4) and phosphate (PO 4) networks were identified through the FTIR analysis. The nature of the metal-ligand bonding and the electronic band structure has been investigated using the absorption spectra. The Judd-Oflet (JO) intensity parameters (X 2 , X 4 and X 6) were evaluated, and the experimental oscillator strength values were also calculated. Using the JO intensity parameters, radiative properties like radiative transition probability (A) stimulated emission cross section r E p and branching ratios b R ð Þ for the emission transitions of the Dy 3? ions have been calculated. The luminescence spectra exhibit two visible bands of 4 F 9/2 ? 6 H 15/2 (Blue) and 4 F 9/2 ? 6 H 13/2 (Yellow). The decay time of the 4 F 9/2 level has been measured from the decay profiles and compared with the calculated lifetimes. The yellow-to-blue (Y/B) ratios and color coordinates have been calculated from the luminescence spectra and can be considered for white light emitting diodes applications.
Structural and luminescence behavior of Er3+ ions doped Barium tellurofluoroborate glasses
Er3+ doped Barium tellurofluoroborate glasses (BTFBxE) with the chemical composition (30 x)TeO2 + 30B2O3 + 20BaO + 20BaF + xEr2O3 (where x = 0.01, 0.05, 0.1, 0.5, 1.0 and 2.0 in wt%) were prepared following the melt quenching technique. The different vibrational modes of borates and tellurites in the prepared glasses were explored through FTIR and Raman spectra. The optical absorption spectra have been used to determine the ionic/covalent nature of the metal–ligand bond in the prepared glasses with the help of Nephelauxetic ratio (b) and bonding parameter (d) studies. The optical band gap of direct and indirect allowed transitions were determined from Tauc’s plot and the variations of band gap energy with structural arrangements were discussed. The Urbach energy values were determined and the relatively lower values of the Urbach’s energy reveal the minimal degree of disorderness in the prepared glasses. The oscillator strengths (fexp and fcal) and Judd–Ofelt (JO) intensity parameters (X2, X4 and X6) were calculated with the application of JO theory and the trends of the JO intensity parameters are found to be X2 > X6 > X4 for all the prepared glasses with a minimum variation in X2 intensity parameter values. A bright green emission was observed from the 2H11/2 + 4S3/2?4I15/2 transition and the radiative properties such as transition probability (A), stimulated emission cross-section (rEP ), branching ratio (br) and radiative lifetime (s) were calculated using the JO parameters. The suitability of the prepared glasses for the fabrication of photonic devices were also discussed and reported in the present work.
Bulletin of Pure and Applied Sciences, 2020
A series of glasses by melting quenching method fabricated for spectroscopic investigations of Dysprosium (Dy 3+) particle ions deposited on Antimony (Sb)-Magnesium (Mg)-Strontium (Sr) Oxyfluoroborate (BSbMgfSr) glasses. The structural and optical characterizations such as XRD, UV-VIS-NIR absorption spectroscopy, photoluminescence (PL) (excitation and emission) were accomplished to study the properties of prepared glasses. The transitions from lowest energy state to an excited state in RE 3+ ions were identified using optical UV-NIR absorption spectra. By the use of Judd-Ofelt theory the J-O intensity parameters Ωλ (λ = 2, 4, 6) have been evaluated utilizing the absorption spectra with the determination of experimental (fexp) and calculated (fcal) oscillator strengths. The emission of light from glass system was concluded through PL spectra (Excitation and emission) for Dy 3+ ion. The radiative properties resembling radiative transition probability (AR), radiative-lifetime (τR), and branching-ratio (β) of the glasses have also estimated. Stimulated emission cross-section (σse) of the glasses also calculated for the feasibility of lasing applications. Experimental lifetime (τexp) of the decay curves of the BSbMgfSrD glasses were also calculated upon excitation by suitable wavelengths of all various concentrations of the RE 3+ ions.
Dy 3+ doped B 2 O 3 -Li 2 O -CaO -CaF 2 glass for efficient white light emitting sources
In this present work, Dy 3+ doped B 2 O 3-Li 2 O-CaO-CaF 2 (BLCFDy) glasses with variable concentrations of alkaline and alkaline earth oxide elements are prepared. The X-Ray diffraction technique has been carried out to verify the non crystallinity of BLCFDy glasses. The Fourier Transform Infrared (FT-IR) study reveals that, the structural properties of glasses exhibiting stretching and vibrational groups of various borate groups. The Optical absorption spectroscopy in Ultraviolet-Visible and Near Infrared regions provides glasses have strong absorption in NIR region for excitations 6 H 15/2 → 6 F 7/2 (895nm), 6 F 9/2 (1084nm), 6 H 9/2 (1267nm) and 6 H 11/2 (1686nm) states. The Optical band gap measurements prove existence of non-bridging oxygens (NBOs), localization of charges and donor centres in prepared glass samples. Judd-Ofelt hypothesis and intensity parameters (Ω 2 , Ω 4 andΩ 6) predicts higher degree of symmetry in covalency and encompassing environment of Dy 3+ ions with constituent ligand elements. The radiative properties of glass samples like radiative transition probability (A R), branching ratios both calculated and experimental (β cal & β rad), peak band width (∆λ p), stimulated emission crosssection and gain band width (σ se x ∆λ p) predicts that prepared glasses are good host of lasing materials and optical gain medium. The Photoluminescence emission spectra exhibits two principle strong emissions at 484nm (Blue), 575nm (Yellow) and observable emission at 664nm (Red) owing to de-excitation from 4 F 9/2 to respective 6 H 15/2 , 6 H 13/2 and 6 H 11/2 states. CIE-1931 chromaticity coordinates (x, y) and CCT values are calculated from photoluminescence emission spectra were found to be within the white light region of the CIE. For the glasses BLCFDy2 and BLCFDy3 colour coordinates (x, y) are (0.34, 0.37), (0.34, 0.38) respectively. The corresponding CCT values are 5223K and 5237K. Thus, BLCFDy2 and BLCFDy3 are the potential candidates for fabrication of white light emitting diodes (W-LEDs) also as laser host materials.
Compositional dependence of white light emission in Dy3+ doped NaCl−BaO bismuth borate glasses
Journal of Luminescence, 2019
The present study deals with synthesis, characterization and analysis of dysprosium doped NaClBaOBi 2 O 3 B 2 O 3 glass samples so as to evaluate its feasibility in solid state lighting applications. Various analytical investigations viz. X-ray diffraction (XRD), density, molar volume measurement, Fourier Transfer Infrared (FTIR) Spectroscopy, UV-Vis-NIR and photoluminescence (PL) has been carried out to study the impact of replacing BaO by NaCl content on white light emission parameters in the host glass matrix. The glassy nature of the prepared samples was confirmed through peak free X-ray diffraction profiles. FTIR spectroscopy reveals the network modifier role of NaCl as four coordinated boron are converted into three coordinated ones. Six absorption peaks from 6 H 15/2 ground state to 4 I 15/2 , 6 F 5/2 , 6 F 7/2 , 6 F 9/2 , 6 H 9/2 , 6 H 11/2 excited states were observed from UV-Vis-NIR spectra of all glass samples. The fundamental absorption edge, optical band gap and Urbach energy were calculated and reported in the present study. Excitation spectra recorded at 578 nm provide six excitation peaks at 349, 363, 386, 425, 452, 471 nm. The highly intense peak at 452 nm was further selected to record the emission spectra and four prominent peaks centred at 484 nm (blue), 578 nm (yellow), 668 nm (red) and 755 nm due to various 4 F 9/2 6 H J (J= 9/2, 11/2, 13/2, 15/2) radiative transitions in visible and near infrared region of the spectra were observed. From emission spectra various parameters viz. Y/B ratio, (x,y) chromaticity coordinates, and correlated color temperature (CCT) were determined. The Y/B ratio for all the glass samples was found to be greater than 1 signifying a covalent bonding between Dy 3+ and O 2ions. The obtained (x,y) coordinates shows a balanced white emission (0.36, 0.39) which is quite stable with varying compositions. The value of CCT for present glass system was found to lie between 43394537 K which is a characteristic of near the white light region marking the suitability of synthesized glasses as an alternative materials for solid state lightening applications.
A Series of Alkaline-Earth Boro Tellurite (AEBT) glasses doped with different concentrations of Dy 3+ ions have been prepared by using melt quenching technique and characterized using spectroscopic techniques such as XRD, Raman, optical absorption, excitation, photoluminescence (PL) and PL decay to understand their utility in optoelectronic devices such as lasers and white light emitting diodes (wLEDs). The XRD spectrum revealed noncrystalline nature whereas the Raman spectrum revealed the phonon energy and various functional groups present in the undoped host glass. The intensities of the electronic transitions and the ligand field environment around the Dy 3+ ions were studied by applying Judd-Ofelt (J-O) theory to the recorded absorption spectra of the AEBTDy glasses. The J-O parameters were used to measure various radiative parameters for the prominent fluorescent levels of Dy 3+ ions in the asprepared glasses. The emission spectra of Dy 3+ ions doped AEBT glasses under 387 nm excitation show three emission transitions 4 F 9/2 → 6 H 15/2 (blue), 4 F 9/2 → 6 H 13/2 (yellow), and 4 F 9/ 2 → 6 H 11/2 (red) of which the yellow transition observed at 575 nm is highly intense. The fluorescence decay curves for the as prepared glasses have been recorded for 757 nm transition under 387 nm excitation wavelength. The experimental lifetimes (τ exp ) measured from the decay spectral profiles are combined with radiative lifetimes (τ R ) to measure quantum efficiencies of the asprepared glasses. The yellow to blue intensity ratios and chromaticity color co-ordinates are found to vary with Dy 3+ ion concentrations. All the aforementioned results finally revealed that the AEBT glasses doped with Dy 3+ ions are aptly suitable for the design and development of optoelectronic devices such as wLEDs and lasers.