Synthesis and optical characterization of Eu2+,Tb3+-codoped Sr3Y(PO4)3 green phosphors

A series of Eu~(2+),Tb~(3+)-codoped Sr_3 Y(PO_4)_3(SYP) green phosphors were synthesized by hightemperature solid-state reaction. Several techniques, such as X-ray diffraction, UV-vis spectrum,and photoluminescence spectrum, were used to investigate the obtained phosphors. The present study investigates in detail photoluminescence excitation and emission properties, energy transfer between the two dopants, and effects of doping ions on optical band gap. SYP:0.05 Eu2+ phosphor shows an intense and broad excitation band ranging from 220 to 400 nm and exhibits a bright green emission band with CIE chromaticity coordinates(0.189, 0.359) under 350 nm excitation. Green emission of SYP:0.03 Tb3+ is intensified by codoping with Eu~(2+), and energy transfer mechanism between them is demonstrated to be a dipole-dipole interaction. Upon 350 nm excitation, SYP:Eu~(2+),Tb~(3+) phosphors exhibits two dominating bands peaking at 466 and 545 nm, which are assigned to 4 f~65 d~1→4 f~7 transition of Eu~(2+) ions and ~5 D_4→~7 F_5 transition of Tb~(3+) ions, respectively. Optimal doping concentrations of Eu~(2+) and Tb~(3+) in the SYP host are 5 mol% and 15 mol%, respectively. Results indicate that SYP:Eu~(2+),Tb~(3+) phosphors are potentially used as green-emitting phosphors for white light-emitting diodes.     

Luminescent ionic lattice occupation and wide tunable emission spectra of La2MgZrO6:Bi3+,Eu3+ double perovskite phosphors for white light LED

La₂Mg_1-x/2Zr_1-x/2O₆:xBi³⁺(x=0.01-0.035,abbreviated as LMZ:Bi³⁺) and La_2-yMg_0.99Zr_0.99O₆:0.02Bi³⁺,yEu³⁺(y=0.1-0.11,abbreviated as LMZ:Bi³⁺,Eu³⁺) double-perovskite phosphors were prepared through high-temperature solid-phase method.The emission spectrum of LMZ:xBi³⁺(x=0.01-0.035)phosphors excited at 353 nm is asymmetric in the range be...     

Enhanced luminescence efficiency and thermal stability via introduction of non-rare earth Bi3+ in Gd5Si2BO13:Eu3+

A series of Gd₅Si₂BO₁₃:Eu³⁺ and non-rare earth Bi³⁺ ions doped Gd₅Si₂BO₁₃:Eu³⁺ phosphors was successfully synthesized via high-temperature solid-state method,and the as-obtained phosphors were studied on their phase structures,luminescence characteristics,thermal stability and luminescence lifetime.Transient fluorescence spectroscopy data show that the addition of Bi³⁺ can obviously enha...     

Synthesis,photoluminescence properties and thermal investigation by TG-MS of RE(DAS)_3·xH_2O(RE=Eu~(3+),Tb~(3+))

Rare earth(Ⅲ) diphenyl-4-amine sulfonates(RE(DAS)_3·xH_2O,RE=Eu~(3+),Tb~(3+))phosphors were synthesized by precursor method from barium diphenyl-4-amine sulfonate and rare earth sulfates.FTIR,TG/DSC coupled to mass spectrometry(TG/DSC/MS),X-ray powder diffraction(XPD),scanning electron microscopy(SEM) and photo luminesce nce(PL) spectroscopy were utilized to structurally and morphologically characterize the samples.Thermal decomposition of Eu(DAS)_3·7H_2O and Tb(DAS)_3·2H_2O at 973 K under dynamic air atmosphere results in crystalline Eu_2O_2SO_4 and Tb_2O_2SO_4 materials,respectively.Accordingly,MS spectra reveal the liberation of thermal decomposition products of precursors,largely as CO_2,NO_2 and SO_2 gases.The diphenyl-4-amine sulfonate(DAS) ligand demonstrats a good stabilizing property for Eu~(3+) and Tb~(3+) ions.The Eu(DAS)_3·7H_2O and Tb(DAS)_3·2H_2O compounds display efficient red and green emissions,under UV excitation,arising from the ~5D_0→~7F_J(J=0-4) and ~5D_4→~7F_J(J=0-6) transitions of the Eu~(3+) and Tb~(3+) ions,respectively.     

A single-phase full-color phosphor Sr2Ca2La(PO4)3O:Eu2+,Tb3+,Mn2+: Photoluminescence and energy transfer

A single-phase full-color emitting phosphor Sr₂Ca₂La(PO₄)₃O:Eu²⁺,Tb³⁺,Mn²⁺ was synthesized by the high temperature solid-state method. The phase formation, luminescence properties, thermal stability, and energy transfer from Eu²⁺ to Tb³⁺ and Eu²⁺ to Mn²⁺ in Sr₂Ca₂La(PO₄)₃O were investigated in details. Tunable emission color from blue to blueish green or orange can be observed under 365 nm near-ultraviolet excitation based on the energy transfer from Eu²⁺ to Tb³⁺ or Mn²⁺ ions by varying the ratio of Eu²⁺/Tb³⁺ or Eu²⁺/Mn²⁺ ions. White light was obtained with chromaticity coordinates of (0.3558, 0.3500) in the Sr₂Ca₂La(PO₄)₃O:0.04Eu²⁺,0.08Tb³⁺,0.40Mn²⁺ phosphor, suggesting their potential applications in white light emitting diodes.     

Luminescence investigation of Eu~（3＋）-Bi~（3＋） co-doped CaMoO_4 phosphor

A series of Eu³⁺-Bi³⁺ co-doped CaMoO₄ red phosphors were synthesized via the solid-sate reaction method. The crystal structures of the obtained samples were identified by X-ray powder diffraction (XRD). The photoluminescence property was investigated, and the results showed that the intensity of excitation spectra and emission spectra could be changed with different doping ratios of Bi³⁺/Eu³⁺. The proposed explanation of these changes was from the energy transfer between Bi³⁺ and Eu³⁺ and the unbalanced charge from the substitution of Eu³⁺ and Bi³⁺ for Ca²⁺ in CaMoO₄. The obtained samples are a promising red light emitting phosphor for the needs of different excitation sources with near-UV and blue GaN-based chips.     

Site occupation and energy transfer in full color emitting phosphor Ba2Ca(BO3)2:Ce3+(K+),Eu2+,Mn2+

White light-emitting diodes (WLEDs) fabricated by single-phase full color emitting phosphor are an emerging solution for health lighting. The crystallographic site occupation of activators in a proper host lattice is crucial for sophisticated design of such phosphor. Here, we report a high quality white light-emitting phosphor Ba₂Ca(BO₃)₂:Ce³⁺(K⁺),Eu²⁺,Mn²⁺ with spectral distribution covering whole visible region. Blue light emission originates from Ce³⁺ ions occupying preferentially Ba²⁺ site by controlling synthesis conditions. Green and red lights are obtained from Eu²⁺ occupying Ba²⁺ (and Ca²⁺) site and Mn²⁺ occupying Ca²⁺ site, respectively. In this triple-doped phosphor, strong red emission with a low concentration of Mn²⁺ is realized by the efficient energy transfer from Ce³⁺ and Eu²⁺ to Mn²⁺. Furthermore, high quality white light is accomplished by properly tuning the relative doping amount of Ce³⁺(K⁺)/Eu²⁺/Mn²⁺ based on efficient simultaneous energy transfer. The results indicate that Ba₂Ca(BO₃)₂:Ce³⁺(K⁺),Eu²⁺,Mn²⁺ is a promising white light-emitting phosphor in WLEDs application.     

Upconversion multicolor tuning of NaY(WO4)2:Tb3+ with Eu3+ doping

A series of Tb~(3+) and Eu~(3+) co-doped NaY(WO_4)_2 phosphors were synthesized by hydrothermal reactions.The crystal structure,morphology,upconversion luminescent properties,the energy transfer from Tb~(3+) to Eu~(3+)ions and the ~5 D_4→ ~7 F_5 transition of the Tb~(3+) ion in NaY(WO_4)_2:Tb~(3+),Eu~(3+) phosphors were investigated in details.The results indicate that all the synthesized samples are of pure tetragonal phase NaY(WO_4)2.Furthermore,the micrometer-sized needle spheres and excellent dispersion of the particles are obtained by adding polyethylene glycol(PEG-2000) as the surfactant.Phosphors of NaY(WO_4)_2:Tb~(3+),Eu~(3+) exhibit the492 nm blue emission peak,546 nm green emission peak,595 nm orange emission peak and 616 nm red emission peak under 790 nm excitation.The energy transfer from Tb~(3+) to Eu~(3+) is a resonant transfer,in which electric dipole-dipole interaction plays a leading role.By adjusting the doping concentration of Eu~(3+) in NaY(WO_4)_2: 1.0 mol%Tb~(3+),xmol%Eu~(3+) phosphors,the emitting color of UC phosphors can be tuned from green to red.     

Red-emitting CaWO4:Eu3+,Tm3+ phosphor for solid-state lighting: Luminescent properties and morphology evolution

CaWO₄:xEu³⁺,yTm³⁺crystals were obtained by facile synthesis at low temperature by the microwaveassisted hydrothermal method(MAH).The phase formation,morphology,luminescent properties and ene rgy transfer were investigated.The X-ray diffraction(XRD)re sults show the formation of a scheelitelike tetragonal structure without the presence of secondary phases.The growth mechanism of hierarchical micro structures based on self-assembly and Ostwald-ripening processes was evaluated,obtaining different types of morphologies.The luminescence spectra of CaWO₄:Eu³⁺,Tm³⁺at 325 nm excitation show the predominance of red emission at the 5 D0→7 F2(Eu³⁺)transition at 624 nm.This feature signals dominant behavior of the electric dipole type.The presence of Tm³⁺is notably evident in the absorption spectra by the related excitation transitions:3 H6→1 G4,3 H6→3 F3 and 3 H6→3 H4.Color parameters are discussed to characterize CaWO₄:Eu³⁺,Tm³⁺emission.The study of the emission spectrum as a function of the concentration of Eu³⁺(x mol%)and Tm³⁺(y mol%)indicates that the CaWO₄:Eu³⁺,Tm³⁺phosphors show stronger red emission intensity and exhibit the CIE value of x=0.63 and y=0.35.The photoluminescence results show 97%high color purity for CaWO₄:4 mol%Eu³⁺,a high CRI(92%)and a low CCT of 1085 K.These results demonstrate that the CaWO₄:Eu³⁺,Tm³⁺red phosphors are promising as color converters for application in white light-emitting diodes and display devices.     

Study on spectroscopic properties of GdOBr:RE (RE=Eu, Tb, Ce)

Rare earth ions doped gadolinium oxybromide phosphors GdOBr:RE³⁺ (RE=Eu, Tb, Ce) were synthesized by the method of solid-state reaction at high temperature, and the VUV-VIS spectroscopic properties of the phosphors were systematically investigated. Under the excitation of VUV or UV source, the phosphors doped with Eu³⁺ and Tb³⁺ show a bright and sharp emission at around 620 nm corresponding to the forced electric dipole ⁵D₀ → ⁷F₂ transition of Eu³⁺, and at around 544 nm corresponding to the ⁵D₄ → ⁷F₅ transition of Tb³⁺, respectively. For GdOBr:Ce³⁺, a broader and intense emission spanned 370–500 nm corresponding to the d-f transition of Ce³⁺ was observed. The excitation spectra were also analyzed.     

Controlled synthesis and tunable luminescence of NaYF4:Eu3+

High quality NaYF₄:Eu³⁺ luminescent materials were successfully synthesized via a facile template technique by hydrothermal method. The samples were characterized by X-ray powder diffraction (XRD), transmission electron microscopy (TEM) and fluorescence spectroscopy (FS). The incorporating of Eu³⁺ ions into NaYF₄ crystal lattice influenced the symmetry types of NaYF₄ crystals, resulting in phase transformation of NaYF₄ crystals between α and β phase. The pure hexagonal phase of branched NaYF₄: Eu³⁺ was obtained as the Eu³⁺ concentration reached 15 mol.%. In addition, the luminescence color was tuned by changing the doping concentration of Eu³⁺ ions.     

Preparation of Eu2+,Dy3+,Zr4+ ions co-doped strontium aluminate/molybdate multi-optical functional hybrid pigments for anti-counterfeiting

Eu²⁺,Dy³⁺ and Zr⁴⁺ ions co-doped strontium aluminate(i.e.,SrAl₂O₄:Eu²⁺,Dy³⁺,Zr⁴⁺)/molybdate(i.e.,Ho₂MoO₆ or Nd₂MoO₆) with photo-/mechano-luminescence and allochroic effect as multi-optical functional hybrid pigments were prepared via solid state reactions and subsequent mixing.The phosphor and hybrid pigments were characterized by X-ray diffraction,scanning electron...     

Enhanced afterglow performance of CaAl_2O_4:Eu~(2+),Nd~(3+) phosphors by co-doping Gd~(3+)

In order to effectively improve the afterglow properties of CaAl_2 O_4:Eu~(2+),Nd~(3+) phosphors,a series of Ca_(0.982-x)Al_2 O_4:0.012 Eu~(2+),0.006 Nd~(3+),xGd~(3+)(x=0,0.012,0.024,0.036,0.048,0.060 mol) phosphors were prepared by a high-temperature solid-phase approach.Crystalline composition and microstructure were characterized by XRD,TEM,HRTEM,and XPS,luminescence properties were systematically analyzed by fluorescence spectra,afterglow decay curves and TL glow curve.Results show that all of Ca_(0.982-x)Al_2 O_4:0.012 Eu~(2+),0.006 Nd~(3+),xGd~(3+)phosphors belong to monoclinic CaAl_2 O_4,without other cystalline phase.The blue emission at 442 nm is observed,which is assigned to the 4 f~65 d→4 f~7 transition of Eu~(2+) ions.Doping with appropriate amount of Gd~(3+) ions(x=0.036 mol) significantly improves the afterglow properties of phosphors,but the excessive doping of Gd~(3+) induces the fluorescent quenching.The doping of moderate Gd3+changes the traps states,the trap depth varies from 0.598 to 0.644 eV and the trap concentration is also greatly improved,thus significantly improving afterglow performance.     

Single-phase white-emitting and tunable color phosphor Na3Sc2(PO4)3:Eu2+,Dy3+: Synthesis,luminescence and energy transfer

A series of Eu²⁺/Dy³⁺ single doped and co-doped Na₃Sc₂(PO₄)₃ phosphors were synthesized by the high-temperature solid-state method, and their phase, morphology, and luminescence properties were characterized. Under the excitation of 370 nm, the Na₃Sc₂(PO₄)₃:Eu²⁺,Dy³⁺ phosphor can emit white light whose spectrum is composed of a broad emission band centered at 460 nm and the other three peaks at 483, 577, and 672 nm, respectively. There is energy transfer from Eu²⁺ to Dy³⁺ ion in Na₃Sc₂(PO₄)₃:Eu²⁺,Dy³⁺ phosphor due to the good overlap between the emission spectrum of Na₃Sc₂(PO₄)₃:Eu²⁺ and the excitation spectrum of Na₃Sc₂(PO₄)₃:Dy³⁺, which is further confirmed by the fluorescence lifetime decrease of Eu²⁺ ion with the increase of Dy³⁺ concentration. The process of energy transfer is via dipole–quadruple interaction which is confirmed by applying Dexter's theory. By increasing the Dy³⁺ concentration, the color coordinates of the Na₃Sc₂(PO₄)₃:0.01Eu²⁺,xDy³⁺ phosphors can be adjusted from blue to white, and then to yellow. The optimized concentration of Dy³⁺ ions is 4.0 mol%, beyond which the concentration quenching will take place. The Na₃Sc₂(PO₄)₃:Eu²⁺,Dy³⁺ phosphor shows fairly good resistance to thermal quenching behavior, of which the emission intensity at 423 K can maintain 90.3% of the initial value (298 K). These results suggest that the Na₃Sc₂(PO₄)₃:0.01Eu²⁺,xDy³⁺ phosphors have potential applications as the color-tunable or a single-phase white emitting phosphor in white LEDs.     

Photoluminescent properties of Eu3＋ and Tb3＋ codoped Gd2O3 nanowires and bulk materials

In this paper, the Gd2O3：Eu3＋,Tb3＋phosphors with different doping concentrations of Eu3＋and Tb3＋ions were prepared by a hydrothermal method for nanocrystals and the solid-phase method for microcrystals. The interaction of the doped ions with different concentrations and the luminescent properties of the nanocrystals and microcrystals were studied systematically. Their structure and morphology of Gd2O3：Eu3＋,Tb3＋phosphors were analyzed by means of X-ray powder diffraction （XRD）, transmission electron mi-croscopy （TEM） and scanning electron microscopy （SEM）. The photoluminescence （PL） properties of Gd2O3：Eu3＋,Tb3＋phosphors were also systematically investigated. The results indicated that when the concentration of doped Eu3＋was fixed at 1 mol.%, the emis-sion intensity of Eu3＋ions was degenerating with Tb3＋content increasing, while when the Tb3＋content was fixed at 1 mol.%, the emission intensity of Tb3＋ions reached a maximum when the concentration of Eu3＋was 2 mol.%, implying that the energy transfer from Eu3＋to Tb3＋took place. In addition, Tb3＋could inspire blue-green light and the Eu3＋could inspire red light. Therefore co-doping systems by controlling the doping concentration and the hosts are the potential white emission materials.     

Luminescent performance of rare earths doped CaBi2Ta2O9 phosphor

A series of red-emitting phosphors of CaBi₂Ta₂O₉:Pr³⁺ and CaBi₂Ta₂O₉:Eu³⁺ were synthesized by the solid-state reaction method. The crystal structure and photoluminescence properties were investigated by X-ray diffraction (XRD) and photoluminescence spectra. The emission spectra showed that the red emission peaks were located at 622 nm for Pr³⁺ and 615 nm for Eu³⁺, respectively. The optimal doping concentrations for Ca_1?xBi₂Ta₂O₉:xPr³⁺ and Ca_1?yBi₂Ta₂O₉:yEu³⁺ were x=0.02 and y=0.15, respectively. The effect of fluxes (H₃BO₃, NH₄F, CaCl₂ and CaF₂) and charge compensations (Li₂CO₃, Na₂CO₃ and K₂CO₃) on luminescent properties were investigated in detail. It was found that the relative emission intensity of Ca_0.98Bi₂Ta₂O₉:0.02Pr³⁺ with 10 mol.% H₃BO₃ flux was about 2.9 times higher than that of the sample without flux. The relative emission intensity of Ca_0.7Bi₂Ta₂O₉:0.15Eu³⁺, 0.15K⁺ was about the 2.1 times higher than that of Ca_0.85Bi₂Ta₂O₉:0.15Eu³⁺.     

Luminescence properties of Pr3+ and Bi3+ co-doped NaCaTiNbO6 phosphor for red-LEDs

This paper investigates the photoluminescence properties of NaCaTiNbO_6:Pr~(3+) and NaCaTiNbO_6:Pr~(3+),Bi~(3+) phosphors. NaCaTiNbO_6:Pr~(3+) and NaCaTiNbO_6:Pr~(3+),Bi~(3+) powder were synthesized successfully by solid state reaction method. Phase purity was checked using X-ray powder diffractometry(XRD). The excitation and emission spectra were recorded to elucidate the photoluminescence properties of NaCaTiNbO_6:Pr~(3+) and NaCaTiNbO_6:Pr~(3+),Bi~(3+). Furthermore,fluorescence lifetime measurements were performed. The excitation spectra of NaCaTiNbO_6:Pr~(3+) show a main band centered at around 357 nm.The luminescence spectra of NaCaTiNbO_6:Pr~(3+) exhibit a red emission peak at 615 nm from the ~1 D_2→~3 H_4 transition of Pr~(3+) ions. With the introduction of the Bi~(3+) ion into NaCaTiNbO_6:Pr~(3+), the luminescence intensity is enhanced nearly two times. Meanwhile,the absorption band edge of NaCaTiNbO_6:Pr~(3+) is shifted from 380 to 420 nm. Thus, this study shows that the red phosphor NaCaTiNbO_6:Pr~(3+) incorporated with Bi~(3+) is advantageous for light-emitting diode applications.     

Effects of europium concentration on luminescent and scintillation performance of Cs0.2Rb0.8Ca1-xEuxBr3(0≤x≤0.08)crystals

A series of Cs_0.2Rb_0.8Ca_1-xEu_xBr₃(0≤x≤0.08)crystals doped with different concentrations of Eu²⁺were grown using the Bridgman-Stockbarger method.The work describes the influence of Eu²⁺concentration on the luminescent and kinetic properties of Cs_0.2Rb_0.8Ca_1-xEu_xBr₃ crystals,as well as on their scintillation performance.The maximum in the radioluminescence spectra of these crystals shifts from 439 to446 nm with increasing europium concentration.The scintillation decay times of Cs_0.2Rb_0.8Ca_1-xEu_xBr₃ lengthen with the Eu²⁺content.The best light output of 33600photons/MeV is obtained for Cs_0.2Rb_0.8Ca_0.93Eu_0.07Br₃,and the best energy resolution of 6.9%is found for Cs_0.2Rb_0.8Ca_0.94Eu_0.06Br₃.     

Ln3+ (Ln = Eu,Dy) - doped Sr2CeO4 fine phosphor particles: Wet chemical preparation,energy transfer and tunable luminescence

The Sr₂CeO₄:Ln³⁺ (Ln = Eu, Dy) fine phosphor particles were prepared by a facile wet chemical approach, in which the consecutive hydrothermal-combustion reaction was performed. The doping of Ln³⁺ into Sr₂CeO₄ has little influence on the structure of host, and the as-prepared samples display well-crystallized spherical or elliptical shape with an average particle size at about 100–200 nm. For Eu³⁺ ions-doped Sr₂CeO₄, with the increase of Eu³⁺-doping concentration, the blue light emission band with the maximum at 468 nm originating from a Ce⁴⁺ → O²⁻ charge transfer of the host decreases obviously and the characteristic red light emission of Eu³⁺ (⁵D₀→⁷F₂ transition at 618 nm) is enhanced gradually. Simultaneously, the fluorescent lifetime of the broadband emission of Sr₂CeO₄ decreases with the doping of Eu³⁺, indicating an efficient energy transfer from the host to the doping Eu³⁺ ions. The energy transfer efficiency from the host to Eu³⁺ was investigated in detail, and the emitting color of Sr₂CeO₄:Eu³⁺ can be easily tuned from blue to red by varying the doping concentration of Eu³⁺ ions. Moreover, the luminescence of Dy³⁺-doped Sr₂CeO₄ was also studied. Similar energy transfer phenomenon can be observed, and the incorporation of Dy³⁺ into Sr₂CeO₄ host leads to the characteristic emission of ⁴F_9/2 → ⁶H_15/2 (488 nm, blue light) and ⁴F_9/2 → ⁶H_13/2 (574 nm, yellow light) of Dy³⁺. The Sr₂CeO₄:Ln³⁺ fine particles with tunable luminescence are quite beneficial for its potential applications in the optoelectronic fields.     

Luminescence properties of composite material Sr2MgSi2O7:Eu2+,Dy3+/light conversion agent with multilayer structure

In order to improve the red luminescent properties,Sr₂ MgSi₂ O₇:Eu²⁺,Dy³⁺was selected as a blue persistent luminescent donor phosphor,while light conversion agent was utilized to tune the persistent luminescent spectra from blue to red.Composite red luminescent material Sr₂ MgSi₂ O₇:Eu²⁺,Dy³⁺/light conversion agent(SMED/LCA) was fabricated with light conversion agent and Sr₂ M...