Orange-red luminescence of samarium-doped bismuth-germanium-borate glass for light-emitting devices.

Samarium (Sm3+ )-doped glass has sparked a rising interest in demonstrating a noticeable emission in the range of 400-700, which is advantageous in solid-state lasers in the visible region, colour displays, undersea communication, and optical memory devices. This study reports the fabrication of Sm3+ -doped bismuth-germanium-borate glasses were established using a standard melt-quenching technique and inspection by absorption, steady-state luminescence, and transient studies. The typical peaks of Sm3+ ions were detected in the visible range under 403 nm excitation. A strong emission band was detected at 599 nm that resembles the 4 G5/2 →6 H7/2 transition of Sm3+ ions for BGBiNYSm0.5 glass. Furthermore, a reddish-orange (coral) luminescence at 646 nm that resembles the 4 G5/2 →6 H9/2 transition was also perceived. The stimulated emission cross-section of 4 G5/2 level for BGBiNYSm0.5 glass was 0.39 × 10-22  cm2 . Lifetime of the 4 G5/2 level was enhanced for the BGBiNYSm0.5 glass and decreased with an increase in active ion concentrations. The lifetime quenching of ions at the metastable state was because of energy transfer among Sm3+ ions by cross-relaxation channels. Commission Internationale de l'Éclairage (CIE) coordinates were evaluated from the emission spectra. Moreover, all the findings recommend these glass as light-emitting materials in the coral region at 599 nm for solid-state lighting applications.

ZrxCa30-xP70 thermoluminescent bio glass, structure and elasticity.

Phosphate glasses of calcium oxide have been well proved materials for various bio bones and dental implants. However, still there is a lot of scope and demand to produce efficient elastic bio implants and resource. In view of this, ZrxCa30-xP70 phosphate materials are prepared by using melt quenching method. Bio, physical, thermoluminescence and elastic techniques are used to characterize the samples. Additionally, simulated body fluid was prepared and it is used especially for bio techniques. Further, the glasses are taken for different dose (~0, 10, 20 & 50 kGy) of gamma irradiation around half an hour. And again similar techniques are used to characterize the samples. All the findings from bio, physical, thermoluminescence and elastic characterization results are analysed and took for better comparison with previous studies to develop various bio bone (or) bio dental resource. Structural reports suggests that the ZrxCa30-xP70 materials were glassy before immersion in SBF solution and immersed (~720 h) samples are showing partial ceramic nature. The weight loss and pH reports suggests them for alternative bio resource as a bio bones and dental implants. Observed thermal stability, microhardness and elastic modulus evaluations of ZrxCa30-xP70 materials in required standards are also additional advantage. Furthermore, thermoluminiscence (TL) under different γ-irradiation doses is reported for glasses with and without immersing in a simulated body fluid. The glasses lose TL intensity when immersed in simulated body fluid for nearly 720 h. This is useful to modulate bio-behaviour in terms of hydroxyapatite layer growth on the glass surface.

Visible upconversion in Er3+/Yb3+ co-doped LaAlO3 phosphors.

The Er3+ doped and Er3+/Yb3+ co-doped LaAlO3 phosphors have been synthesized by the combustion method and characterized their structural, morphological, elemental, vibrational and optical properties. The optical absorption and upconversion properties of the synthesized phosphors have been studied. Upon co-doping Yb3+ ions into Er3+:LaAlO3, the blue, green and red upconversion emissions of Er3+ ions have been enhanced about ~20, ~54 and ~22 times, under 978nm laser excitation. The observed upconversion emissions could be due to excited state absorption in Er3+:LaAlO3, whereas energy transfer is dominant mechanism in Er3+/Yb3+:LaAlO3 phosphors. The tuning in the color emitted from the synthesized phosphors towards the green region has been found due to incorporation of the Yb3+ ions. With increase in the pump power, the color emitted from the co-doped phosphor is not tuned significantly, showing its applicability in making the green display devices.

Structural, elastic and vibrational properties of nanocrystalline lutetium gallium garnet under high pressure.

An ab initio study of the structural, elastic and vibrational properties of the lutetium gallium garnet (Lu3Ga5O12) under pressure has been performed in the framework of the density functional theory, up to 95 GPa. Pressure dependence of the elastic constants and the mechanical stability are analyzed, showing that the garnet structure is mechanically unstable above 87 GPa. Lattice-dynamics calculations in bulk at different pressures have been performed and compared with Raman scattering measurements of the nanocrystalline Tm(3+)-doped Lu3Ga5O12 up to 60 GPa. The theoretical frequencies and pressure coefficients of the Raman active modes for bulk Lu3Ga5O12 are in good agreement with the experimental data measured for the nano-crystals. The contributions of the different atoms to the vibrational modes have been analyzed based on the calculated total and partial phonon density of states. The vibrational modes have been discussed in relation to the internal and external modes of the GaO4 tetrahedron and the GaO6 octahedron. The calculated infrared modes and their pressure dependence are also reported. Our results show that with this nano-garnet size the sample has essentially bulk properties.

Efficient visible upconversion luminescence in Er3+ and Er3+/Yb3+ co-doped Y2O3 phosphors obtained by solution combustion reaction.

Combustion derived Er(3+) -doped Y2O3 and Er(3+)/Yb(3+)co-doped Y2O3 powders have been characterized by X-ray diffraction, energy dispersive X-ray analysis, Fourier transform infrared spectroscopy and laser excited spectroscopy. Formation of Y2O3 phosphor was confirmed by X-ray diffraction and energy dispersive X-ray analysis. The vibrational properties of Y2O3 powder was studied by Fourier transform infrared spectroscopy. The luminescence spectra of Er(3+) -doped and Er(3+)/Yb(3+) co-doped Y2O3 powders were studied under 379nm excitation. The strong up-conversion luminescence for Er(3+) -doped and Er(3+)/Yb(3+) co-doped Y2O3 powders have been observed under 978nm laser excitation. The effect of Yb(3+) addition on optical and luminescence properties of Er(3+):Y2O3 powders were studied. The ratio of red to green intensity has been enhanced when Er(3+) -doped Y2O3 is co-doped with Yb(3+) ions. The effect of co-doping of Yb(3+) ions on the visible luminescence intensity of Er(3+) has been studied and the mechanism responsible for the variation in the green and red intensity is discussed.

Optical properties of Nd3+ doped bismuth zinc borate glasses.

Glasses with compositions of (100-x) (Bi2ZnOB2O6) -x Nd2O3 (where x=0.1, 0.3, 0.5, 1 and 2 mol%) were prepared by melt quenching method and characterized through optical absorption, emission and decay curve measurements. Optical absorption spectra have been analyzed using Judd-Ofelt theory. The emission spectra exhibit three peaks at 919, 1063 and 1337 nm corresponding to (4)F3/2 to (4)I9/2, (4)I11/2 and (4)I13/2 transitions in the near infrared region. The emission intensity of the (4)F3/2 to (4)I11/2 transition increases with increase of Nd(3+) concentration up to 1 mol% and then concentration quenching is observed for 2 mol% of Nd(3+) concentration. The lifetimes for the (4)F3/2 level are found to decrease with increase in Nd2O3 concentration in the glasses. The decay curves of the glass up to 0.3 mol% of Nd(3+) exhibit single exponential nature and thereafter the curves become nonexponential nature (0.5, 1 and 2 mol%). The nonexponential curve has been fitted to the Inokuti-Hirayama model to understand the nature of energy transfer process.

Intense up-conversion luminescence in Er3+/Yb3+ co-doped CeO2 powders.

The Er(3+) and Er(3+)/Yb(3+) co-doped CeO2 powders have been prepared by a urea combustion route. The structural, morphological, compositional and vibrational analysis of the Er(3+):CeO2 and Er(3+)/Yb(3+):CeO2 powders have been studied by X-ray diffraction, scanning electron microscopy, energy dispersive X-ray and Fourier transform infrared spectroscopy. The optical and luminescence properties of Er(3+):CeO2 and Er(3+)/Yb(3+):CeO2 powders have been studied by using laser excited spectroscopy. The effects of Yb(3+) doping on up-conversion luminescence of Er(3+) co-doped CeO2 powders were studied. The ratio of red to green intensity is decreased in Er(3+):CeO2 whereas the ratio is increased in Er(3+)/Yb(3+):CeO2 powders with increase of power. The effect of co-doping with the Yb(3+) ions on the visible luminescence of Er(3+) and the energy transfer mechanism responsible for the variation in the green and red intensity are discussed. The results indicate that these materials may be suitable for display and light emitting devices.

Structural and luminescence properties of Ho(3+)/Yb(3+)-doped Lu3Ga5O12 nano-garnets for phosphor applications.

Lu3Ga5O12 nano-garnet powders doped with Ho(3+)/Yb(3+) ions have been prepared using a citrate sol-gel technique. The structural and morphological properties have been investigated by X-ray diffraction, scanning electron microscopy and Fourier transform infrared spectroscopy. The materials are found to exist in single phase of cubic garnet structure with an average particle size of around 45 nm. The Ho(3+)/Yb(3+)-doped Lu3Ga5O12 nano-garnet powders give rise to an intense green and weak red emission of Ho3+ ions under 457.5 nm direct excitation. Moreover, when the Yb3+ ions are excited at 950 nm a very bright green luminescence of the Ho3+ ions is observed by the naked eyes even for such low laser power as 10 mW and the intensity of the red emission have been increased compared to that found under direct excitation of the Ho3+ ions. The power dependency and dynamics of the infrared-to-visible upconverted luminescence confirm the existence of different two-photon energy transfer processes. All these results have been compared with those obtained for other garnets doped with similar lanthanide ions which suggest that the Lu3Ga5O12 nano-garnets are potential materials for light emitting devices.

Nanocrystalline lanthanide-doped Lu3Ga5O12 garnets: interesting materials for light-emitting devices.

Nanocrystalline Lu(3)Ga(5)O(12), with average particle sizes of 40 nm, doped with a wide variety of luminescent trivalent lanthanide ions have been prepared using a sol-gel technique. The structural and morphological properties of the powders have been investigated by x-ray powder diffraction, high resolution transmission electron microscopy and Raman spectroscopy. Structural data have been refined and are presented for Pr(3+), Eu(3+), Gd(3+), Ho(3+), Er(3+) and Tm(3+) dopants, while room temperature excited luminescence spectra and emission decay curves of Eu(3+)-, Tm(3+)- and Ho(3+)-doped Lu(3)Ga(5)O(12) nanocrystals have been measured and are discussed. The Eu(3+) emission spectrum shows typical bands due to 5D(0)-->7F(J) (J = 0, 1, 2, 3, 4) transitions and the broadening of these emission bands with the non-exponential behaviour of the decay curves indicates the presence of structural disorder around the lanthanide ions. Lanthanide-doped nanocrystalline Lu(3)Ga(5)O(12) materials show better luminescence intensities compared to Y(2)O(3), Gd(3)Ga(5)O(12) and Y(3)Al(5)O(12) nanocrystalline hosts. Moreover, the upconversion emission intensity in the blue-green region for the Tm(3+)- and Ho(3+)-doped samples shows a significant increase upon 647.5 nm excitation with respect to other common oxide hosts doped with the same lanthanide ions.

Role of the local structure and the energy trap centers in the quenching of luminescence of the Tb3+ ions in fluoroborate glasses: a high pressure study.

The concentration and pressure dependent luminescence properties of the Tb(3+) ions in a lithium fluoroborate glasses have been studied by analyzing the deexcitation processes of the (5)D(4) level at ambient conditions as well as a function of pressure up to 35 GPa at room temperature. The luminescence spectra of Tb(3+) ions have been measured as a function of pressure and observed a continuous redshift as well as a progressive increase in the magnitude of the crystal-field splittings for the (5)D(4)-->(7)F(3,4,5) transitions. Monitoring the (5)D(4)-->(7)F(5) transition, the luminescence decay curves have been measured and analyzed in order to understand the dynamics of the deexcitation of the Tb(3+) ions in these glasses. At ambient conditions a nonexponential behavior has been found for doping concentrations as low as 0.1 mol % of Tb(4)O(7), although no cross-relaxation channels exist to explain this behavior. The modelization of the energy transfer processes surprisingly shows that the nonexponential character of the decay curves of the (5)D(4) level with concentration or with pressure has to be ascribed to energy transfer to traps without migration of energy between Tb(3+) ions. For all the experimental situations the nonexponential character of the decay curves is well described by the generalized Yokota-Tanimoto model with a dipole-dipole interaction between the Tb(3+) ions and the nearby luminescence quenching traps. The luminescence properties observed with releasing pressure are slightly different to those obtained while increasing pressure suggesting a local structural hysteresis in the lithium fluoroborate glass matrix giving rise to the generation of a new distribution of environments for the Tb(3+) ions.

Luminescence properties of Sm(3+)-doped P(2)O(5)-PbO-Nb(2)O(5) glass under high pressure.

Samarium doped lead phosphate glass modified with niobium having a composition (in mol%) of 55P(2)O(5)+39.5PbO+5Nb(2)O(5)+0.5Sm(2)O(3) has been prepared by the conventional melt quenching technique. The emission spectra and the decay curves for the (4)G(5/2) level of Sm(3+) ions have been measured as a function of pressure up to 23.6 GPa at room temperature. A discontinuity in the observed shifts and crystal-field splittings as a function of pressure around 9-10 GPa suggests that a phase transition is taking place in the glass matrix. The [Formula: see text], (6)H(7/2) and (6)H(9/2) transitions are shifted towards the lower energy side with magnitudes of -7.1, -7.6 and -5.5 cm(-1) GPa(-1) up to 8.9 GPa (phase 1) and -5.6, -4.9 and -4.4 cm(-1) GPa(-1) beyond 10.3 GPa (phase 2), respectively. A much stronger increase in the splitting of the [Formula: see text] and [Formula: see text] Stark levels with pressure is observed in phase 1 than in phase 2. The lifetime of the (4)G(5/2) level decreases from 2.29 ms (0 GPa) to 0.64 ms (23.6 GPa) with pressure. The decay curves of the (4)G(5/2) level exhibit non-exponential behavior for all the pressures and were fitted by the generalized Yokota-Tanimoto model to probe the nature of the energy transfer process. The best fits with S = 6 indicate that the energy transfer between donor and acceptor is of dipole-dipole type. The crystal-field splitting experienced by the Sm(3+) ions in the title glass are found to be larger than those found in borate, K-Ba-Al phosphate and tellurite glasses.

Fluorescence properties of Eu3+ ions doped borate and fluoroborate glasses containing lithium, zinc and lead.

The influence of glass composition on the fluorescence properties of Eu3+ ions doped borate and fluoroborate glasses modified with Li+, Zn2+ and Pb2+ cations have been investigated. The magnitude of splittings of 7F1 levels are analyzed using crystal-field (CF) analysis. The relative intensities of 5D0 --> 7F2 to 5D0 --> 7F1 transitions, crystal-field strength parameters and decay times of the 5D0 level have been determined and are found to be lower for Pb based glasses than those of Zn/Li based glasses. The lifetimes of 5D0 level are found to increase when borate glasses are modified with pure fluorides than with oxides and oxyfluorides. The fluorescence decay of 5D0 level fits perfect single exponential in the Eu3+:glass systems studied which indicates the absence of energy transfer between Eu3+ ions in these glasses.