Increase In Dy3 Research Articles

White light emission from Dy3+ doped sodium–lead borophosphate glasses under UV light excitation

Sodium–lead borophosphate glasses doped with different Dy3+ concentrations have been prepared and characterized through, XRD, FTIR, optical absorption and photoluminescence techniques. FTIR spectrum indicates the presence of BO3 and PO4 structural units. The optical absorption spectrum has been studied at room temperature and several bands have been observed. These bands have been assigned to the ground state 6H15/2 to several excited states. The bonding parameters have been evaluated based on the observed band positions. From the absorption spectrum, Judd–Ofelt (J–O) intensity parameters have been evaluated. By using J–O parameters radiative parameters such as transition probabilities, branching ratios and absorption cross section have been evaluated. The emission spectra have been studied for different concentrations of Dy3+ ions. The yellow/blue values due to 4F9/2→6H13/2/4F9/2→6H15/2 luminescence intensity ratios of Dy3+ ions, increase with increasing concentrations, suggesting higher asymmetry and more covalent bonding character between Dy and oxygen ligands. The chromaticity coordinates were calculated from emission spectra and analysed with Commission International deI’Eclarige Color diagram. The life time of the 4F9/2 level has been measured and found to decrease with increase in Dy3+ ions concentration.

Synthesis and luminescent properties of Eu3+ and Dy3+ doped BiPO4 phosphors for near UV-based white LEDs

The phosphors BiPO4:Eu3+ co-doped with Dy3+ were synthesized by the conventional solid-state reaction method. XRD and scanning electron microscopy results showed that the crystalline phase of the samples BiPO4:Eu3+ transforms from high-temperature monoclinic phase to low-temperature monoclinic phase with the increase of Dy3+ concentration. The photoluminescence properties of the samples showed that the colors shifting from red–orange area to blue–green area are close to those of ideal white light by readjusting the doping concentration ratio of Eu3+ and Dy3+. The Eu3+and Dy3+ doped BiPO4 phosphors may be potential applications in white light near-UV light-emitting diodes.

Optical and luminescence properties of Dy3+ ions in phosphate based glasses

Phosphate glasses with compositions of 44P2O5 + 17K2O + 9Al2O3 + (30 − x)CaF2 + xDy2O3 (x = 0.05, 0.1, 0.5, 1.0, 2.0, 3.0 and 4.0 mol %) were prepared and characterized by X-ray diffraction (XRD), differential thermal analysis (DTA), Fourier transform infrared (FTIR), optical absorption, emission and decay measurements. The observed absorption bands were analyzed by using the free-ion Hamiltonian (HFI) model. The Judd–Ofelt (JO) analysis has been performed and the intensity parameters (Ωλ, λ = 2, 4, 6) were evaluated in order to predict the radiative properties of the excited states. From the emission spectra, the effective band widths (Δλeff), stimulated emission cross-sections (σ(λp)), yellow to blue (Y/B) intensity ratios and chromaticity color coordinates (x, y) have been determined. The fluorescence decays from the 4F9/2 level of Dy3+ ions were measured by monitoring the intense 4F9/2 → 6H15/2 transition (486 nm). The experimental lifetimes (τexp) are found to decrease with the increase of Dy3+ ions concentration due to the quenching process. The decay curves are perfectly single exponential at lower concentrations and gradually changes to non-exponential for higher concentrations. The non-exponential decay curves are well fitted to the Inokuti–Hirayama (IH) model for S = 6, which indicates that the energy transfer between the donor and acceptor is of dipole–dipole type. The systematic analysis of revealed that the energy transfer mechanism strongly depends on Dy3+ ions concentration and the host glass composition.

Structure and multiferroic properties of Bi(1-x)DyxFe0.90Mg0.05Ti0.05O3 solid solution

Chemical modification is proven to be an effective way to improve the properties of perovskite BiFeO3 (BFO). In this paper, we studied the effects of the A-site Dy3+ ion substitution on the structure and multiferroic properties of BFO in which the Fe3+ ion on the B-site is partially co-substituted for by Mg2+ and Ti4+ ions. The solid solution compounds of Bi(1-x)DyxFe0.90Mg0.05Ti0.05O3 (x = 0 – 1) were synthesized by a tartaric acid-assisted solution process, followed by thermal treatments at 850 °C. The structural transition and the ferroelectric and magnetic properties as a function of composition were investigated. It is found that the structure transforms from a rhombohedral (R3c) to an orthorhombic phase (Pn21a) when x is increased to ≥ 0.15. The ferroelectric measurements indicate that the sample with x = 0.15 possesses the best ferroelectric property, and the remnant polarization of the samples with orthorhombic symmetry decreases with the increase of Dy3+ concentration. The compounds of Bi(1-x)DyxFe0.90Mg0.05Ti0.05O3 (x = 0.05 – 1.00) exhibit weakly ferromagnetic properties at low temperatures, but antiferromagnetic behavior at high temperatures. The magnetization of the solid solution increases linearly with the increase of the Dy3+ amount.

Optical properties of zincfluorophosphate glasses doped with Dy3+ ions

Abstract Dy3+-doped zincfluorophosphate glasses with composition (in mol%) 44P2O5+17K2O+(30−x) ZnF2+9Al2O3+xDy2O3, x=0.01, 0.5, 1.0 and 2.0 have been prepared by melt quenching technique and were characterized through absorption, emission, excitation spectra and decay curves analysis. The energy levels obtained in the absorption spectrum have been analyzed by using free-ion Hamiltonian model. From the intensities of absorption spectra, Judd–Ofelt intensity parameters have been evaluated and in turn predicted the radiative properties such as radiative transition probability, radiative lifetime and branching ratios. The decay curves are found to be single exponential for lower concentrations (≤0.1 mol%) and turns into non-exponential for higher concentrations. The non-exponential decay curves are well fitted to Inokuti–Hirayama model for S=6, which indicates that the energy transfer between the donor and the acceptor is of dipole–dipole nature. The fluorescence lifetime decreases from 0.82 ms to 0.45 ms with increase in Dy3+ ion concentration from 0.01 to 2.0 mol%. The results obtained for PKAZFDy glasses are compared and discussed with the other reported Dy3+: glasses. The chromaticity properties for different concentrations of PKAZFDy glass were calculated from emission spectra and analyzed with Commission International de I'Eclairage (CIE) color diagram.

Combustion synthesis, structural characterization, thermo and photoluminescence studies of CdSiO3:Dy3+ nanophosphor

CdSiO3:Dy3+ (1–9mol%) nanophosphors were prepared for the first time using the solution combustion method. The process of monoclinic phase formation was investigated by PXRD, TG–DTA and FTIR. The results show that the phase formation temperature of combustion-derived monoclinic CdSiO3 is found to be lower as compared to the powders prepared by solid-state and sol–gel methods. It was observed that the average crystallite size calculated by Debye–Scherrer's formula and Williamson–Hall (W–H) plot are well comparable and was found to be in the range of 35–70nm. Scanning electron micrographs indicate that there exist circular microcrystalline particles. It is observed that the optical energy gap is widened with the increase of Dy3+ ion dopant. The photoluminescence (PL) spectra exhibit characteristic transitions of Dy3+ due to 4F9/2→6H15/2 (blue) and 4F9/2→6H13/2 (yellow) regions. The thermoluminescence (TL) glow curve of CdSiO3:Dy3+ nano powder exposed to UV irradiation exhibited one main peak centered at 170°C. The intensity of the main peak increases up to the dose of 20min then it decreases. The glow curves were analyzed by the glow peak shape method and the estimated trap parameters are discussed.

Dysprosium doped lead fluoroborate glasses: Structural, optical, and thermal investigations

AbstractDy3+ doped lead fluoroborate (LFB) glasses (B2O3 + PbO + PbF2) have been prepared following conventional melt quenching technique by varying the concentration of Dy2O3 in the order 0.01, 0.1, 1, 2, and 3 mol%. X‐ray powder diffraction (XRD), Fourier transform infrared (FTIR), optical absorption, fluorescence emission, and decay curves have been recorded and analyzed. From the optical measurements and based on the Judd–Ofelt (JO) theory, the JO intensity parameters were evaluated and in turn used to evaluate the radiative transition probabilities (A), stimulated emission cross‐section ($\sigma _{{\rm P}}^{{\rm E}} $), radiative lifetimes (τrad), and branching ratios (βR) for the various 4F9/2 → 6HJ (J = 11/2, 13/2, 15/2) transitions of Dy3+ ions in the LFB glasses and these values were compared with the other reported Dy3+:glasses. The decay curves of the 4F9/2 level were measured and found to be deviate from the exponential nature with the increase in Dy3+ ion concentration. The luminescence quantum efficiency of the 4F9/2 level was also determined and discussed. Differential scanning calorimetry (DSC) curves were used to evaluate the glass stability factor (S) and Hruby's parameter (HR) through the glass transition (Tg), crystallization (Tc), and melting (Tm) temperatures and these results were discussed and reported.

Controllable white light emission from Dy3+–Eu3+ co-doped KCaBO3 phosphor

Potassium calcium borate, KCaBO3:Eu3+ phosphors with various Dy3+ concentrations (0–3 wt%) were synthesized by solid state reaction and studied for the first time. Under various UV–violet excitations, the obtained single monoclinic phased Dy3+–Eu3+ co-doped KCaBO3 polycrystalline phosphors emit a combination of yellow–blue and red–orange wavelength giving intense white light, which can easily be controlled by varying the concentration of Dy3+. The increase in white light emission with the increase of Dy3+ concentration indicates the efficient energy inter-ion transfer from Dy3+ to Eu3+ ions. Furthermore, the observed emission lifetimes and the intense white light emission are suggestive exploration for the present phosphor for potential optoelectronic applications such as white light-emitting phosphor for blue LEDs chips.

Effects of Dy<sup>3+</sup>/ Eu<sup>2+</sup> Molar Ration on SrAl<sub>2</sub>O<sub>4</sub>：Eu<sup>2+</sup>，Dy<sup>3+</sup>Long Persistence Phosphors by Microwave Plasma Synthesisd Method

SrAl2O4:Eu2+, Dy3+ long persistence phosphors are synthesized by microwave plasma method. The effects of molar ratio of Dy3+ and Eu2+ on the phase composition, the spectrum properties and long afterglow property of phosphors are investigated in the paper. The analysis results show that spectrum properties depressed clearly following the increase of Dy3+/ Eu2+. And the afterglow property of phosphors are improved by doping of the Dy3+, but suppressed by excessive doping. On the one hand, this is because that the number of electrons trapped by defect levels increased with the increase of Dy3+. But on the other hand, it’s difficult to occur electric transition if doping excessive Dy3+, so leads to performance depressed. Above-mentioned results, it’s confirm that the optimized Dy3+/Eu2+ molar ratio is 2:1 when SrAl2O4:Eu2+, Dy3+ phosphors synthesized by microwave plasma method.

Optical properties of Dy3+-doped sodium–aluminum–phosphate glasses

Trivalent dysprosium (Dy3+)-doped sodium–aluminum–phosphate (NAP) glasses were prepared and characterized by their optical absorption, excitation, emission spectra, and decay time measurements. Judd–Ofelt intensity parameters were derived from the absorption spectrum and used to calculate the radiative lifetime and stimulated emission cross section of the 4F9/2 → 6H13/2 and 4F9/2 → 6H15/2 transitions. The luminescence intensity ratio of 4F9/2 → 6H13/2 to 4F9/2 → 6H15/2 transitions of Dy3+ in NAP glasses gives the feasibility of extracting white light. The lifetime and quantum efficiency of 4F9/2 level is found to be higher than other reported glasses. With increase in Dy3+ ion concentration, the decay from 4F9/2 level is found to be faster with decrease in lifetime due to cross relaxation between Dy3+ ions.

Synthesis, characterization and photoluminescence properties of CaSiO3 : Dy3+ nanophosphors

CaSiO3 : Dy3+ (1–5 mol. %) nanophosphors were synthesized by a simple low-temperature solution combustion method. Powder X-ray diffraction patterns revealed that the phosphors are crystalline and can be indexed to a monoclinic phase. Scanning electron micrographs exhibited faceted plates and angular crystals of different sizes with a porous nature. Photoluminescence properties of the Dy3+-doped CaSiO3 phosphors were observed and analyzed. Emission peaks at 483, 573 and 610 nm corresponding to Dy3+ were assigned as 4F9/2 → 6H15/2, 4F9/2 → 6H13/2 and 4F9/2 → 6H11/2 transitions, respectively, and dominated by the Dy3+ 4F9/2 → 6H13/2 hyperfine transition. Experimental results revealed that the luminescence intensity was affected by both heat treatment and the concentration of Dy3+ (1–5 mol. %) in the CaSiO3 host. Optimal luminescence conditions were achieved when the concentration of Dy3+ was 2 mol. %. UV–visible absorption features an intense band at 240 nm, which corresponds to an O–Si ligand-to-metal charge transfer band in the group. The optical energy band gap for the undoped sample was found to be 5.45 eV, whereas in Dy3+-doped phosphors it varies in the range 5.49–5.65 eV. The optical energy gap widens with increase of Dy3+ ion dopant.

Preparation and luminescence characteristics of SrAl2B2O7:Dy3+ phosphor

The SrAl2B2O7:Dy3+ phosphor is synthesizd through a general high temperature solid-state reaction, and its luminescence properties are investigated. The emission spectrum of SrAl2B2O7:Dy3+ shows the bands at 480nm,573nm and 678nm under the 365nm excitation, corresponding to the 4F9/2→6H15/2,4F9/2→6H13/2 and 4F9/2→6H11/2 typical transitions of Dy3+ respectively. The excitation spectrum for 573nm emission has excitation bands at 295 nm,325 nm,350 nm,365 nm and 400nm. The influence of doped Dy3+ contentration on the emission spectrum and the luminescent intensity of SrAl2B2O7:Dy3+ is investigated. The result shows that the intensity ratio of yellow emission (573nm) to blue emission (483 nm), Iy/Ib, increases with the increase of Dy3+ concentration, which may be explained by the Judd-Ofelt theory. The luminescent intensity increases first with the increase of Dy3+ concentration, then decreases. The concentration self-quenching is attributed to the d-d interaction according to the Dexter theory. The introducing of charge compensation agents of Li+, Na+ and K+ ions can augment the emission intensity. It is found that Li+ ions are the best to enhance the emission intensity.

Luminescence properties of Dy<SUP align=right>3+</SUP> doped Gd<SUB align=right>2O<SUB align=right>3 nanoparticles prepared by glycine route: annealing effect

Dy3+ doped Gd2O3 nanoparticles were prepared by glycine-nitrate combustion route and their luminescence properties have been investigated. Through host lattice absorption at 230 nm, emission peaks at 488 (4F9/2 → 6H15/2, blue-green) and 572 nm (4F9/2 → 6H13/2, yellow) of Dy3+ are observed along with a broad emission peak at 400 nm (host). Luminescence intensity increases with increase of heat-treatment from 500°C to 900°C due to extent of reduction of particle surface defect. On increasing the concentration from 1 to 2 at.% Dy3+, luminescence intensity increases slightly and decreases with further increase of Dy3+ due to cross-relaxation among Dy3+ ions. This was supported by lifetime studies. Lifetimes for 4F9/2 level of Dy3+ in 1, 2 and 5 at.% Dy3+ doped Gd2O3 prepared at 900°C were found to be 237, 39 and 26 μs, respectively.

Lifetime and quantum yield studies of Dy3+ doped GdVO4 nanoparticles: Concentration and annealing effect

GdVO 4 nanoparticles doped with Dy3+ have been prepared using urea hydrolysis method in ethylene glycol medium. Linear decrease in the unit cell volume indicates the quantitative substitution of Gd3+ lattice sites by Dy3+ in GdVO4. The luminescence intensity of electric dipole transition at 573 nm is more than that of magnetic dipole transition at 483 nm. This has been attributed to the asymmetric environment of Dy3+ ion in GdVO4. Luminescence intensity decreases with increasing Dy3+ concentrations due to concentration quenching. This is supported by lifetime decay studies. There is no particle size effect on the peak positions of Dy3+ emission. There is an increase in the decay lifetime for F49/2 level with increase in heat treatment from 500 to 900 °C. This is attributed to the reduction in nonradiative process arose from surface inhomogeneities. The decay lifetime data follow the biexponential to monoexponential nature with increase of Dy3+ concentrations. There is an increase in the quantum yield with the increase in heat treatment temperature.