Molten salt synthesis and photoluminescence properties of novel red emitting phosphors Ba5(VO4)3Cl:Eu3+,K+

A series of Ba₅(VO₄)₃Cl:Eu³⁺,K⁺ phosphors have been synthesized by the molten salt synthesis method. The crystalline structure, morphology, photoluminescence properties and lifetimes were characterized using X-ray diffraction (XRD), field emission scanning electron microscope (FE-SEM) and photoluminescence spectroscopy, respectively. XRD indicates that the Ba₅(VO₄)₃Cl:Eu³⁺,K⁺ phosphors are synthesized successfully via molten salt method. SEM image demonstrates that the obtained phosphors have hexagonal polyhedron morphology. The photoluminescence spectra reveal that the as-prepared phosphors exhibit a bright red emission under the excitation of blue or near ultraviolet light. The concentration quenching was also investigated, and the dipole–dipole interaction is responsible for the concentration quenching of fluorescence emission of Eu³⁺ ions in Ba₅(VO₄)₃Cl phosphor. The present work suggests that the Ba₅(VO₄)₃Cl:Eu³⁺,K⁺ phosphors would be a potential candidate for light emitting devices.     

Luminescence and Optical-Memory model of SrAl2O4:Eu2+,Dy3+ and Sr4Al14O25:Eu2+,Dy3+

The photoluminescence, luminescence excitation, and phosphorescence spectra of SrAl²O⁴:Eu²⁺,Dy³⁺ and Sr₄Al₁₄O₂₅:Eu²⁺,Dy³⁺ powder phosphors have been studied in detail at 80 and 300 K. A conceptual model is proposed for strontium-aluminate-based optical memory.     

Greatly improved photoluminescence properties of the electrodeposited Y2O3:Eu thin film phosphors by the addition of Na and K ions

In this work, Y₂O₃:Eu³⁺ thin film phosphors were prepared by electro-deposition method. The effect of Na⁺ and K⁺ ions on the photoluminescence properties of Y₂O₃:Eu³⁺ thin film phosphor was studied in details. It was found that the addition of Na⁺ and K⁺ ions could improve the photoluminescence intensity by 3 to 4 times. The highly improved photoluminescence intensity may be caused by different factors. The improved crystallinity and the increased optical volume caused by the flux effect of Na⁺ and K⁺ ions could be the major reasons for the enhanced photoluminescence intensity. It was also found that the average lifetime of Y₂O₃:Eu³⁺ thin film phosphors could be adjusted by the molar amount of Na⁺ and K⁺ ions.     

Single-component and white light-emitting phosphor BaAl2Si2O8: Dy3+, Eu3+ synthesis,luminescence, energy transfer,and tunable color

A series of Dy³⁺ - Eu³⁺ co-doped BaAl₂Si₂O₈ phosphors were prepared via the conventional solid-state reaction method. Their crystal structure, luminescent characteristic and lifetime were investigated. The optimum doping concentrations of Dy³⁺and Eu³⁺ are both 0.05 for Dy³⁺ or Eu³⁺ singly doped BaAl₂Si₂O₈. Furthermore, BaAl₂Si₂O₈: 0.05Dy³⁺ and BaAl₂Si₂O₈: 0.05Eu³⁺ emits yellow and red light. The emission color of BaAl₂Si₂O₈: Dy³⁺, Eu³⁺ could be tuned from yellow to white due to the energy transfer. This energy transfer from Dy³⁺ to Eu³⁺ was confirmed and investigated by photoluminescence spectra and the decay time of energy donor Dy³⁺ ions. With constantly increasing Eu³⁺ concentration, the energy transfer efficiency from Dy³⁺ to Eu³⁺ in BaAl₂Si₂O₈ host increased gradually and reached as high as 81%, the quantum yield was about 47.43%. BaAl₂Si₂O₈: Dy³⁺, Eu³⁺ phosphors can be effectively excited by UV (about 348 nm) light and emit visible light from yellow to white by altering the concentration ratio of Dy³⁺ and Eu³⁺, indicating that the phosphors have potential applications as a white light-emitting phosphor for display and lighting.     

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.     

Comparative study of Ca3Bi(PO4)3:Eu3+ phosphors prepared by three methods

Ca₃Bi(PO₄)₃:Eu³⁺ phosphors were synthesized by solid-state (SS) reaction, co-precipitation (CP) and sol–gel methods. The resulting phosphors were well characterized by X-ray diffraction, field-emission scanning electron microscopy and photoluminescence spectra. The X-ray diffraction results suggested that the pure phase of Ca₃Bi(PO₄)₃:Eu³⁺ can be obtained by SS reaction and CP method. The phosphors obtained by CP method showed more homogeneous, agglomerate-free particles. The samples obtained by the CP method showed the highest emission intensity among the three methods which fired at 1,000 °C for 2 h. It was showed that the CP method was the most respected process for the preparation of Ca₃Bi(PO₄)₃:Eu³⁺ phosphors.     

Luminescence of SrGdGa3O7:RE(RE = Eu, Tb) phosphors and energy transfer from Gd to RE

Eu³⁺- and Tb³⁺-activated SrGdGa₃O₇ phosphors were synthesized by the solid-state reaction and their luminescence properties were investigated. Sr(Gd_1 − xEu_x)Ga₃O₇ and Sr(Gd_1 − xTb_x)Ga₃O₇ formed continuous solid solution in the range of x = 0-1.0. Unactivated SrGdGa₃O₇ exhibited a typical characteristic excitation and emission of Gd ion. The SrGdGa₃O₇:xEu³⁺ and SrGdGa₃O₇:xTb³⁺ phosphors also showed the well-known Eu³⁺ and Tb³⁺ excitation and emission. The energy transfer from Gd³⁺ to Eu³⁺ and Tb³⁺ were verified by photoluminescence spectra. The dependence of photoluminescence intensity on Eu³⁺ and Tb³⁺ concentration were also studied in detail and the photoluminescence (PL) intensity of SrGdGa₃O₇:Eu and SrGdGa₃O₇:Tb were compared with commercial phosphors, Y₂O₃:Eu and LaPO₄:Ce,Tb. The luminescence decay measurements showed that the lifetimes of Eu³⁺ and Tb³⁺ were in the range of microsecond. The energy transfer from Gd³⁺ to Tb³⁺ was also observed in decay curve.     

Photoluminescence properties of a novel red-emitting phosphor Ba<Subscript>2</Subscript>LaV<Subscript>3</Subscript>O<Subscript>11</Subscript>:Eu<Superscript>3+</Superscript>

Ba₂LaV₃O₁₁:Eu³⁺ phosphors were firstly synthesized by the traditional solid-state reaction method at 1100 °C. Their luminescence properties were investigated by photoluminescence excitation and emission spectra. The excitation spectrum shows a broad band centered at about 275 nm in the region from 200 to 370 nm, which is attributed to an overlap of the charge transfer transitions of O^2??→?V⁵⁺ and O^2??→?Eu³⁺. The phosphors exhibit the red emissions of Eu³⁺ and the emission intensity ratio of ⁵D₀?→?⁷F₂ to ⁵D₀?→?⁷F₁ is dependent on the Eu³⁺ concentration due to an environment change about Eu³⁺ ions. Concentration quenching occurs at 30 mol% in the phosphors and exchange interaction is its main mechanism. Ba₂LaV₃O₁₁:Eu³⁺ displays tunable CIE color coordinates from yellow orange to red depended on Eu³⁺ content, which may have a potential application for illuminating and display devices.     

Synthesis and luminescence properties of monodisperse SiO2@SiO2:Eu3+ microspheres

Monodisperse core–shell structured SiO₂@SiO₂:Eu³⁺ microspheres were synthesized in a seeded growth way. In that way, a thin shell of Eu³⁺-doped silica was grown on the prepared monodisperse silica colloids. The samples were characterized by scanning electron microscopy (SEM), transmission electron microscopy (TEM), energy-dispersive X-ray spectrometry (EDX), X-ray diffraction (XRD), Fourier transform infrared spectrum (FT-IR), thermal analysis (TGA-DSC) and photoluminescence (PL) spectroscopy. The results reveal that the SiO₂ spheres have been successfully coated by SiO₂:Eu³⁺ phosphors and the obtained SiO₂@SiO₂:Eu³⁺ particles have perfect spherical shape with narrow size distribution. Additionally, the monodisperse SiO₂@SiO₂:Eu³⁺ microspheres exhibit considerably strong photoluminescence (PL) of Eu³⁺ under the excitation of 393 nm compared with the SiO₂:Eu³⁺ samples with polydispersed or irregular shapes and sizes obtained by base-catalyzed Stöber method. Furthermore, the PL intensity increases with the increasing of Eu³⁺ concentration in SiO₂ microspheres shell, and concentration quenching occurs when Eu³⁺ concentration exceeds 5.0 mol%.     

Investigation on photoluminescence properties and defect chemistry of GdAlO3:Dy3+ Ba2+ phosphors

GdAlO₃:Dy³⁺ Ba²⁺ phosphors are synthesized by citrate-based sol-gel method. Photoluminescence and positron annihilation studies are used to investigate the emission and defect chemistry of the phosphors respectively. The strong yellow (Dy³⁺) emission properties of phosphors are discussed for various concentrations of Dy³⁺ ions. Upon the addition of Ba²⁺ ion, an enhancement in emission intensity is observed due to the lattice distortions around Dy³⁺ ion. The positron studies indicate the presence of defects at crystallite boundaries, vacancy clusters and large voids in the materials. The influence of Ba²⁺ ion on the photoluminescence and lattice distortion around Dy³⁺ is also explored.     

Effect of Al ions on fluorescence properties of YPO4: Eu phosphors

Different concentrations of Al³⁺-doped YPO₄:Eu_0.05 powder phosphors have been synthesized by the conventional solid state reaction method and are characterized by X-ray diffraction (XRD), field emission scanning electronic microscopy (FESEM), photoluminescence excitation (PLE) and emission (PL) investigations. The influence of Al³⁺-doping on crystallinity, grain size and PL intensity of the YPO₄:Eu phosphors has been investigated. These characteristics are found improved with increase in concentration of Al³⁺ ions from 0.00 to 0.10 mol and then decreased for higher concentrations. The results are discussed in comparison with earlier reported similar works.     

Photoluminescence properties of Eu doped Ba2ZnS3 phosphor for white light emitting diodes

The synthesis and photoluminescence properties of novel Eu²⁺ doped Ba₂ZnS₃ phosphors for white light emitting diodes (LEDs) are reported. Diffuse reflection spectra of Ba₂ZnS₃ host and synthesized phosphors have been measured. The excitation spectra of synthesized phosphors consist of three broad bands between 250 nm and 550 nm and are consistent with the diffuse reflectance spectra. The emission spectra show the characteristic 4f⁶5d¹ → 4f⁷ transition of Eu²⁺ ion and there exists efficient energy transfer from host to Eu²⁺ ions when excited by 350-nm light. The dependence of emission spectra on temperature is also measured; the possible reasons applied to explain the experimental results are also discussed. The fluorescence lifetime of Eu²⁺ in Ba_1.995ZnS₃:0.005Eu²⁺ is measured and the values are 1.49 and 23.4 μs.     

Synthesis and luminescence properties of novel β-Zn3BPO7:Ln (Ln = Ce3+, Eu2+, Eu3+) phosphors

This work first reports the synthesis and luminescence properties of rare earth Ce³⁺, Eu²⁺, Eu³⁺ ions doped β-Zn₃BPO₇ phosphors [β-Zn₃BPO₇:Ln (Ln = Ce³⁺, Eu²⁺, Eu³⁺)]. The phosphors were synthesized by a solid-state reaction at high temperature, and their luminescence properties were investigated by measuring the photoluminescence excitation and emission spectra. The f–d transitions of Ce³⁺ and Eu²⁺ ions in the host lattice are assigned and corroborated, which lead to the broad emission band in ultraviolet (UV) and visible region for Ce³⁺ and Eu²⁺ ions under UV excitation, respectively. Typical reddish orange emission from Eu³⁺ in the host lattice was also observed. The spectroscopic characteristics including Stokes shift, crystal field depression, electron–vibrational interaction, and charge transfer band were investigated and compared with that in other borophosphate phosphors. β-Zn₃BPO₇:Eu²⁺ and β-Zn₃BPO₇:Eu³⁺ phosphors show potential application in solid state lighting region.     

Study of the effect of Li<Superscript>+</Superscript> concentration on the photoluminescence properties of Y<Subscript>2</Subscript>O<Subscript>3</Subscript>:Eu<Superscript>3+</Superscript> phosphors

Y₂O₃:Eu³⁺ phosphors were prepared by hydrothermal method. Effect of the doping concentration of Eu³⁺ on the photoluminescence properties of Y₂O₃:Eu³⁺ phosphor was studied in details. It was found that the strongest emission intensity is achieved as atomic ratio of Y³⁺ to Eu³⁺ is 8. As concentration of Eu³⁺ exceeds the critical concentration, the emission intensity decreases dramatically due to the concentration quenching of Eu³⁺. Also, the effect of Li⁺ on the photoluminescence performance of the Y₂O₃:Eu³⁺ phosphor is studied in this work. According to the results, the doping of Li⁺ may greatly improve the PL performance of the Y₂O₃:Eu³⁺ phosphors due to the flux effect and improved crystallinity caused by the doping of Li⁺.     

Luminescent properties of YAl3(BO3)4:Eu3+ phosphors

YAL₃(BO₃)₄:Eu³⁺ phosphors were fabricated by the sol-gel method. The structure properties were measured by x-ray diffraction (XRD) and infrared spectra (IR). Doping concentration of Eu³⁺ ions in YAL₃(BO₃)₄:Eu³⁺ phosphors of 0, 1, 3, 4, and 5 mol% were studied. The excitation spectra and emission spectra of YAL₃(BO₃)₄:Eu³⁺ phosphors were examined by fluorescent divide spectroscopy (FDS). The luminescent properties of YAL₃(BO₃)₄:Eu³⁺ phosphors are discussion. The optimal doping concentration of Eu³⁺ ions in YAL₃(BO₃)₄:Eu³⁺ phosphors was found to be approximately 3 mol%.     

Synthesis and luminescence properties of YVO4:Eu cobblestone - like microcrystalline phosphors obtained from the mixed solvent - thermal method

The mixed solvent-thermal method has been developed for the synthesis of YVO₄:Eu³⁺ luminescent materials in the N, N-dimethylformamide (DMF)/ de-ionized water (DIW) solution. The samples have been characterized by X-ray diffraction (XRD), scanning electron microscopy (SEM), transmission electronic microscope (TEM), UV/vis absorption and photoluminescence spectroscopies. The results demonstrate that we have obtained the uniform YVO₄:Eu³⁺ cobblestone - like microcrystalline phosphors in the mixed solution of DMF and DIW, which are different to the as-obtained YVO₄:Eu³⁺ nanoparticles in pure DIW. And the as - prepared YVO₄:Eu³⁺ microcrystalline particles are composed of numerous nanoparticles. The assembling phenomenon of the nanoparticles is strongly affected by the pH value of the solution and the volume ratio of DMF/DIW. Under UV excitation, the samples can emit the bright red light. While, the photoluminescence (PL) intensities of YVO₄:Eu³⁺ show some difference for samples obtained under the different reaction conditions. This is because that different microstructures of samples result in different combinative abilities between the surface and the adsorbed species so as to produce the different quenching abilities to the emission from Eu³⁺ ions.     

Synthesis and photoluminescence of nano-Y2O3:Eu phosphors

We report nano-Y₂O₃:Eu³⁺ phosphors with particle size of about 50 nm and relatively high photoluminescence (PL) intensity which is close to the standard for application. The influences of the dope amount, the surfactant and the precipitation pH on the PL intensity, the particle size and the dispersion have been studied. It has been found that 4% is the best Eu³⁺ molar concentration to get the highest PL intensity for both nano- and micro-Y₂O₃:Eu³⁺. The addition of butanol as a surfactant inhibits the grain growth and the agglomeration of particles efficiently by reducing the oxygen bridge bonds. As the pH rises, the PL intensity and the particle size increase due to the formation of oxygen bridge bonds.     

Influence of Zn2+ and Si4+ codoping on luminescence properties of CaWO4:Eu3+ phosphor

The red afterglow phosphors of CaWO₄ doped with Eu³⁺, Zn²⁺ or (and) Si⁴⁺ were prepared by solid state reaction. All crystalline phases were identified by the X-ray powder diffraction (XRD). The photoluminescence spectra and decay curves as well as thermoluminecence (TL) curves of all samples were also investigated. In comparison to CaWO₄:Eu³⁺ phosphor, the luminescence and afterglow properties could be improved greatly after being doped with Zn²⁺ or (and) Si⁴⁺ ions.     

Optical properties of Eu<Superscript>3+</Superscript> activated SrLa<Subscript>2</Subscript>O<Subscript>4</Subscript> red-emitting phosphors for WLED applications

The SrLa_2?xO₄:xEu³⁺ phosphors are synthesized through high-temperature solid-state reaction method at 1473 K with various doping concentration. Their phase structures, absorption spectra, and luminescence properties are investigated by X-ray diffraction (XRD), UV–Vis spectrophotometer and photoluminescence spectrometry. The intense absorption of SrLa_2?xO₄:xEu³⁺ phosphors have occurred around 400 nm. The prominent luminescence spectra of the prepared phosphors exhibited bright red emission at 626 nm. The doping concentration 0.12 mol% of Eu³⁺ is shown to be optimal for prominent red emission and chromaticity coordinates are x?=?0.692, y?=?0.3072. Considering the high colour purity and appropriate emission intensity of Eu³⁺ doped SrLa₂O₄ can be used as red phosphors for white light emitting diodes (WLEDs).     

Photoluminescence mechanisms of color-tunable Sr2CeO4: Eu3+, Dy3+ phosphors based on experimental and first-principles investigation

We report single-phased color-tunable phosphors (Sr₂CeO₄: Eu³⁺, Dy³⁺) synthesized by a polymer-network gel method for UV–LED. The photoluminescence properties and possible energy transfer mechanisms of Eu³⁺ and Dy³⁺ in Sr₂CeO₄ were investigated by experiments and first principles calculations. The results show that the ⁵D₀ → ⁷F₂ emission of Eu³⁺ is enhanced by the increase in the amount of Eu³⁺ ions and Eu³⁺ substitution makes more stable defect than Dy³⁺ substitution does. The photoluminescence mechanism of Sr_1.994−xEu_xDy_0.006CeO₄ can be explained by the energy transfer model with the consideration of the defect conditions in the crystals.