Nd3+ doped BBZPA glasses were prepared by conventional melt quenching method and used to study their structural, absorption, emission and decay properties. From XRD, amorphous nature of the undoped glass has been confirmed. The J-O intensity parameters Omega(lambda) (lambda = 2, 4, 6) and the various radiative parameters were calculated from J-O analysis. From the emission spectra, it is observed that, the laser transition F-4(3/2) -> I-4(11/2) at 1059 nm is more intense transition. The decay curves for prepared glasses exhibited single exponential decay. The above results suggest that Nd3+ doped BBZPA glasses could be suitable for photonic applications. (C) 2018 Elsevier Ltd.

A new series of Er doped bismuth borate glasses were prepared with the chemical composition of 5Bi2O3 (65-x) B2O3 – 10ZnO 10Pb3O4 10AlF3 xEr2O3 (where x = 0.0, 0.1, 0.5, 1.0, 2.0 and 3.0 mol %) using the melt quenching technique. The prepared glasses were characterized by XRD, absorption, luminescence and decay spectral analysis. From XRD spectra, the amorphous and homogeneous nature of the prepared bismuth borate glasses was confirmed. The physical and optical properties of the prepared glass samples were determined. From the intensities of absorption bands, the Judd-Ofelt analysis has been applied to determine the intensity parameters Ωλ (λ = 2, 4 and 6) and the trend of these parameters has been observed as Ω2 > Ω6 >Ω4 and are used to calculate the various radiative parameters of the I13/2 → I15/2 emission transition of Er ions. The normalized NIR emission spectra for the I13/2 → I15/2 transition of Er doped BBZPA glasses with various Er2O3 concentrations under 980 nm laser excitation were recorded in the wavelength region 1400 – 1700 nm. It has been observed that the spectra exhibited strong emission at 1530 nm corresponding to I13/2 → I15/2 transition. The other relative parameters such as stimulated emission crosssection (σe ), optical gain (G), gain band width (∆G) were calculated. The recorded fluorescence decay curves of the I13/2 → I15/2 transition of the Er‐ doped BBZPA glasses exhibited single exponential nature upto 1.0 mol% and then turned into nonexponential for 2.0 and 3.0 mol% of Er ions concentrations. These results suggest that the present BBZPAEr1.0 glass system could be suitable for optical amplifier applications at 1.53μm. Index Terms Bismuth borate glasses, XRD, Absorption, J-O parameters; emission spectra; decay time.

In the present work, neodymium (Nd) doped lead borosilicate glasses (NLBS) were prepared using the various chemical constituents such as PbO, H3BO3, SiO2, Al2O3, LiF and Nd2O3 by the conventional melt-quenching method. The structural properties of the NLBS glasses were investigated through the X-ray diffraction (XRD), Fourier transform Infrared (FTIR) spectral measurements; whereas the optical properties such as intensity parameters (Ωλ), radiative transition probabilities (AR), total transition probability (AT), radiative lifetime (τR) and branching ratios (βR) have been determined from the UV-VIS-NIR absorption and emission spectra. From the XRD analysis, the amorphous nature of NLBS glasses has been confirmed and the functional groups as well as the co-existence of trigonal BO3 and tetrahedral BO4 units are identified from the IR spectra. The experimental and calculated oscillator strengths (fexp & fcal) and the evaluated Judd-Ofelt (JO) intensity parameters (Ωλ, λ = 2, 4 and 6) were determined from the absorption spectrum and compared with the other Nd doped host glasses. From the recorded emission spectra, three NIR bands identified at 903, 1060 and 1334 nm corresponding to the F3/2→I9/2, F3/2→I11/2 and F3/2 →I13/2 transitions, respectively for which the effective bandwidths (ΔλP), radiative transition probabilities (AR), branching ratios (βR), and stimulated emission cross-sections (σe) were also evaluated. The intensities of emission bands increased with the increase of Nd ions concentration upto 1.0 mol% and then decreased at higher concentrations due to the concentration quenching. From the results of these investigations, it is concluded that the Nd doped LBS glasses could be useful for various photonic applications in different fields.

White emitting Na3Gd(PO4)2 nanocrystalline phosphors doped with trivalent dysprosium (Dy3+) ions were synthesized by using citrate gel combustion technique. The structure of the compound is found to be orthorhombic with a particle size is 10 nm. Luminescence properties have been characterized using photoluminescence (PL), excitation, emission spectra and decay time measurements. In emission spectrum sharp emission peaks were observed 4F9/2 → 6H15/2 (blue) and 4F9/2 → 6H13/2 (yellow) transition of Dy3+ ions. From the concentration dependent PL studies, the optimum concentration of Dy3+ ions in Na3Gd(PO4)2 is found to be 1.0 mol %, where intense near white light for 352 nm pump wavelength. The yellow to blue intensity ratios, CIE chromaticity coordinates and correlated color temperature studies has shown the possibility of using this phosphor for W-LEDs

Er3+-doped phosphate based glasses were prepared by the conventional melt-quenching technique with the chemical composition of 44 P2O5 - 17 K2O - 9 Al2O3 - (30-x) CaF2 - x Er2O3, (where x = 0.1, 0.5,1.0, 2.0 and 3.0 mol %) and their spectral properties have been investigated from absorption, emission and decay measurements. The phenomenological Judd - Ofelt intensity parameters Omega(lambda)(lambda = 2, 4, 6) were determined from the intensities of absorption bands in order to calculate the radiative transition probability (A(R)), radiative lifetime (tau(R)), branching ratios (beta(R)) of various excited states. The McCumber's theory has been adopted to predict, the emission cross-section (sigma(M)(e)) of I-4(13/2) -> 4I(15/2) transition from the absorption cross-section (sigma(a)) of the I-4(13/2) ? I-4(13/2) transition of Er3+ ions. From near infrared emission spectra, full width at half maxima (FWHM), stimulated emission cross-section (sigma(e)) and gain bandwidth (Delta G) for the I-4(13/2) -> I-4(15/2) emission transition at 1.536 mu m were evaluated and discussed their utility for optical communication networks. (C) 2016 Elsevier B.V. All rights reserved.

Yttrium borate phosphors (KY(1−x)DyxBO3) doped with Dy3+ ions were synthesized by the solid-state reaction method. The structural and morphological characteristics were studied by XRD, FTIR and SEM measurements. Luminescent properties of different concentrations of KY(1−x)DyxBO3 phosphors were investigated from the excitation, emission and decay analyses. The emission spectra exhibited characteristic blue (460–500nm) and yellow (555–610nm) bands of Dy3+ ions which combines to give white light. The evaluated color co-ordinates (x, y) were found to lie within the white light region of CIE chromaticity diagram. All the decay curves of Dy3+ ions exhibited non-exponential nature and the experimental lifetimes for the 4F9/2 excited level were found to decrease from 0.87, 0.47, 0.35, 0.26 and 0.13ms with the increase of Dy3+ ion concentrations from 0.05, 0.1, 0.15, 0.2 and 0.3mol%, respectively. In order to understand the energy transfer mechanism, the decay curves were fitted to Inokutti-Hirayama model and found that the energy transfer is of dipole-dipole type. From the results of these investigations, it is concluded that the KY(1−x)DyxBO3 phosphors are more useful for white light emitting diodes.

Neodymium doped phosphate based glasses with composition of (P2O5+K2O+Al2O3+CaF2) were prepared. The samples were analysed through differential thermal analysis (DTA), Fourier transform infrared (FTIR), absorption, emission and decay measurements. Judd-Ofelt parameters (Ωλ) have been determined from the spectral intensities of absorption bands in order to calculate the radiative parameters like radiative transition probabilities (AR), radiative lifetime (τR) and branching ratios (βR) for the 4F3/2→4I11/2 laser transition of Nd3+ ion. The effective emission bandwidths (Δλeff), experimental branching ratios (βexp) and stimulated emission cross-sections (σe) have been determined from the emission spectrum. The decay curves of the 4F3/2 level exhibited almost single exponential nature for all the Nd3+ ion concentrations.

Red emitting new phosphor, YBO3 doped with Eu3+ ions, has been prepared by solid state reaction method. The excitation spectra were recorded by monitoring a red emission at 610 nm and observed very intense band in the lower wavelength region, 230 ~ 280 nm, which could be attributed due to the Eu3+-O2- charge transfer band (CTB) lying in the band gap region of the host matrix. In addition to the CTB, strong absorption lines in the excitation spectrum is located at 395 nm and 465 nm which corresponds to the 7F0 → 5L6 and 7F0 → 5D2 transitions of Eu3+ ions, respectively. The decay curves are found to be single exponential at lower concentrations and tends to be non-exponential at higher concentrations with shortening of lifetime (2.74 ms to 0.86 ms). The systematic investigation indicates that this Eu3+-doped YBO3 phosphor is an ideal candidate for solid state lighting applications.

Lead borosilicate (LBS) glasses doped with different concentrations of Dy3+ ions (0.1, 0.5, 1.0 and 2.0mol%) were synthesized by the conventional melt quenching method. The prepared glasses were characterized through X-ray diffraction (XRD), optical absorption and photoluminescence spectra. The glassy nature of LBS host glass has been confirmed from XRD analysis and the Judd–Ofelt (JO) intensity parameters (Ωλ, λ=2, 4 and 6) have been calculated from the intensities absorption bands. The evaluated parameters are then used to calculate radiative properties such as radiative transition probabilities (AR), total transition probability (AT), radiative lifetime (τR) and branching ratios (βR) for the excited 4F9/2 level of Dy3+ ions. From the emission spectra, the effective band widths (Δλeff), stimulated emission cross-sections (σ(λp)), yellow to blue (Y/B) intensity ratios, experimental lifetimes (τexp) of 4F9/2 metastable state and the chromaticity color coordinates for white light emission have been determined and discussed.

Photoluminescence properties of singly doped Tm3+ and co-doped Tm3+/Tb3+ ions in TZKC glasses with chemical composition of (61.5−x) TeO2+25 ZnO+8 K2O+5CaO+0.5Tm2O3+xTb4O7 (TZKCTm05Tbx; x (in mol%)=0, 0.5, 1.0, 1.5) have been studied. The experimental oscillator strengths of absorption bands in TZKCTm05 glass were used to determine the host dependent Judd–Ofelt Ω2, Ω4, Ω6 intensity parameters. The effective emission cross-section of 1.8μm emission band as a function of wavelength has been deduced by the McCumber’s theory. Based on the absorption (σa) and emission cross-sections (σe), the gain co-efficients (G) of 1.8μm emission band for various population inversions between the emitting (3F4) and terminating (3H6) levels were evaluated. From the photoluminescence spectra of singly doped Tm3+ and co-doped Tm3+/Tb3+ ions in TZKC glasses, the chromaticity color coordinates (x, y) were estimated.

Eu3+-Dy3+ co-doped Na3Gd(PO4)(2) phosphors were prepared by the solid state reaction method at high temperature. The structural and surface morphological properties have been studied using X-ray diffraction and scanning electron microscopy techniques. The energy dispersive spectrum (EDS) and Fourier transform infrared (FTIR) spectrum were recorded to understand the elemental and vibrational analysis respectively. The energy transfer efficiency from Dy3+ to Eu3+ ions has been calculated. From the emission spectra, the CIE chromaticity color coordinates (x, y) were evaluated in order to predict the colors emitted by the phosphors. It is concluded that the emission color of the titled phosphor depends on the doping concentrations of Eu3+-Dy3+ ions.

Optical absorption and near-infrared luminescent properties of Nd3+ ions doped oxyfluorosilicate (NKZLSNd) glasses were investigated. Raman spectrum was recorded to investigate the structural properties of NKZLSNd glasses. The Judd–Ofelt theory (JO) has been applied to the absorption spectrum of 1.0mol% Nd3+-doped oxyfluorosilicate glass to derive the JO intensity parameters (Ωλ), which are in turn used to calculate the radiative properties of Nd3+ ions luminescent levels. The near-infrared emission spectra recorded with 808nm laser diode excitation revealed the effective bandwidths values around 30–40nm for the 4F3/2 level of Nd3+-doped oxyfluorosilicate glasses. The measured decay times of 4F3/2 level decreased with increasing Nd3+ ions concentration due to the concentration quenching.

A series of YAB:Eu3+/Tb3+ co-activated phosphors of composition Y(1−x−y)Al3(BO3)4:xEu3+/yTb3+ (x=0, 0.3, 0.5, 1, 2% and y=0.5%) were prepared by solid-state reaction method and their photoluminescence properties were characterized. Eu3+/Tb3+ co-doped phosphors have shown their excellent luminescent properties in their respective emission regions. The YAB:2%Eu3+ phosphor under 395nm excitation exhibited red luminescence with Commission International de I'Eclairagein chromaticity coordinates (x=0.627, y=0.334) which are close to an ideal red and commercial Y2O3:Eu3+ red phosphor chromaticity coordinates. The emission color of Eu3+/Tb3+ co-doped phosphors has been tuned from pale-green to white as a function of Eu3+/Tb3+ concentration. Moreover, the Tb3+ acts as an efficient sensitizer and enhances the luminescence of Eu3+ by transferring absorbed excitation energy. The overlapping 7F0→5D3,2,1,0(Eu3+); 7F1→5D1,0(Eu3+); 7F2→5D1(Eu3+) excitation and 5D3→7F5,4,3 (Tb3+); 5D4→7F5,4(Tb3+) emission transitions revealed the transfer of energy from Tb3+ to Eu3+ through exchange interaction mechanism in Eu3+–Tb3+ clusters instead of from these ions randomly distributed in YAB lattice. The YAB:Eu3+/Tb3+ phosphors have potential in the field of display technology.

Dy3+–Tm3+ ions codoped SrMg2La2W2O12 (strontium magnesium lanthanum tungstate) phosphors were synthesized by conventional high‐temperature solid‐state reaction method. X‐ray analysis of the end products revealed the well‐crystallized phases with orthorhombic structure. The functional groups present in the phosphors were studied by the Fourier transform infrared measurements. To know the potential applicability of these phosphors for white light emission, the excitation and emission spectra were recorded. The excitation spectra exhibited an intense broad band at 313 nm, pertaining to the O → W ligand‐to‐metal charge‐transfer state (LMCT) of the host. With the excitation of LMCT band (313 nm), the decay curves of singly doped SrMg2La2W2O12:Dy phosphors exhibited single exponential, where as the codoped SrMg2La2W2O12:DyTm phosphors exhibited double exponential nature. The luminescence colors of these phosphors were estimated from Commission Internationale de L'Eclairage (CIE) coordinates using the photoluminescence data. The color of singly doped SrMg2La2W2O12:Dy phosphor has been tuned by codoping with Tm3+ ions. It has been noticed that the CIE chromaticity coordinates (x,y) determined from the luminescence spectrum of singly Dy3+ doped SrMg2La2W2O12 phosphor shifted toward the white light region, when codoped with Tm3+ ions. The increase in correlated color temperatures (Tcct) has been noticed with the increase of Tm3+ ions concentration in SrMg2La2W2O12:DyTm phosphors.

Structural and spectral properties of erbium-doped niobium oxyfluorosilicate glasses were characterized by the differential thermal analysis, Raman, infrared, photoluminescence and lifetime measurements. With the increase of Er3+ ions concentration, the lifetime of I-4(13/2) level has been decreased due to the concentration quenching effect. The McCumber.'s theory was adopted to predict the emission cross-section (sigma(M)(emi)) of I-4(13/2) -> I-4(15/2) transition from the absorption cross-section (sigma-abs) of I-4(15/2) -> I-4(13/2) transition of Er3+ ions. The gain parameters such as optical gain, gain bandwidth and gain coefficient for amplification were evaluated for the I-4(13/2) -> I-4(15/2) emission transition (1.54 tm). The Er3+-doped niobium oxyfluorosilicate glass covers both C (1530-1565 nm) and the L (1565-1625 nm) band regions in the optical communication window. From the results of these investigations, it is concluded that the Er3+-doped niobium oxyfluorosilicate glasses are more useful for photonic device applications. (C) 2013 Elsevier B.V. All rights reserved.

This paper reports on the effect of concentration of Eu3+ ions in K2O-Nb2O5-SiO2-Eu2O3 (KNbSiEu) glasses prepared by the melt quenching technique. By using the Judd-Ofelt (JO) theory, the intensity parameters Omega(lambda) (lambda= 2, 4, 6) have been determined from the absorption and emission spectra of Eu3+ ions under different constraints. The radiative properties of some of the excited states of Eu3+ ions have been calculated. The decay curves of D-5(0) level exhibited single exponential for all the Eu3+ ions concentrations. From these results, it is suggested that the strong red emission at 616 nm corresponding to the D-5(0) -> F-7(2) transition could be used for the development of optical display devices. Crown Copyright (C) 2013 Published by Elsevier B.V. All rights reserved.

Eu3+-doped Na3Gd(PO4)(2) phosphors were synthesized by the modified citrate gel combustion technique. From the XRD pattern, structure of the compound was found to be orthorhombic with a particle size of 10-20 nm. The emission spectra revealed that the Na3Gd(PO4)(2):Eu3+ phosphors can be excited effectively by 394 nm pump wavelength. From the concentration dependent photoluminescence studies, the optimum concentration for efficient luminescence of Eu3+ ions in Na3Gd(PO4)(2) phosphor has been found to be 1.5 mol%. Decay curves of the D-5(0) level of Eu3+ ions were recorded by monitoring the emission at 596 nm corresponding to D-5(0) -> F-7(1) transition and are found to be single exponential for all the concentrations. The chromaticity properties for different concentrations of Na3Gd(PO4)(2):Eu3+ nanophosphors were calculated from emission spectra and analyzed in the frame work of CIE color diagram. (C) 2014 Elsevier B.V. All rights reserved.

Zinc Alumino Bismuth Borate (ZnAlBiB) glasses at different compositions doped with 1 mol% of Sm3+ ions were prepared by using the melt quenching technique and investigated by XRD, optical absorption, emission and decay curve analysis to understand the visible luminescence of these glasses. From the absorption spectra the JO parameters are evaluated and are used to calculate the radiative properties such as transition probability, radiative lifetime, branching ratio and absorption cross-sections for various fluorescent levels of Sm3+ ions. The emission spectra of Sm3+ ions doped ZnAlBiB glasses show two intense emission bands 4G5/2→6H7/2 (orange) and 4G5/2→6H9/2 (red) for which the stimulated emission cross-section and branching ratios are evaluated to understand the potentiality of these materials as visible lasers. The decay profiles for the 4G5/2 fluorescent level of Sm3+ doped ZnAlBiB glasses have been recorded to measure the quantum efficiency (η) of these glasses. The strong visible emissions, large stimulated emission cross-sections, high branching ratios and good quantum efficiencies observed for the present ZnAlBiB glasses suggest the suitability of these glasses as laser and photonic devices operating in visible region.