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.     

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.     

Luminescent properties of Ca2SiO4：Eu^3＋ red phosphor for trichromatic white light emitting diodes

The luminescent properties of Eu^3＋doped Ca2SiO4 red phosphors synthesized by the flux fusion reaction method were investigated. It was found that the excitation spectrum included two regions： the weak excitation band below 325 nm and strong narrow peaks above 325 nm. The main peak of the excitation band was located at 400 nm. The peaks located at 290 nm were assigned to the combination of the charge transfer transition of O-Eu, peaks above 325 nm （325, 385, 400, 470, 511, and 539 nm） were assigned to the f-f transitions of Eu^3＋. The emission spectrum was dominated by the red peak located at 612 nm due to the electric dipole transition of ^5D0-^7F2. In addition, the effects of the Eu^3＋ content and charge compensators of Li^＋, Na^＋, K^＋, and Cl^- ions on the emission intensity were investigated. The experiment results suggested that the strongest emission was obtained when the concentration of the Eu^3＋ ions was 0.3 mol^-1, and Li^＋ ions gave the best improvement to enhance the emission intensity. Ca2SiO4：Eu^3＋, Li^＋ was thus suitable for low-cost trichromatic white light emitting diodes （WLED） based on UV InGaN chip.     

Study on spectroscopic properties of GdOBr:RE3+ (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.     

Comparative Study on Photoluminescent Properties of CaGdAlO4：Eu3＋ Phosphors Synthesized with Three Methods

CaGdAlO4 ： Eu^3＋ powder phosphors were prepared using citrate sol-gel （CSG）, haft-dry and half-wet （HDW） and solid state （SS） methods, respectively. X-ray diffraction results confirm the formation of CaGdAlO4：Eu^3＋ at 900 % （CSG）, 1200℃ （HDW） and 1400℃ （SS）, respectively. Field emission scan electron microscopy （FE-SEM） images show that the CaGdAlO4：Eu^3＋ powder prepared by the CSG and HDW method has an elliptical shape and that prepared under the SS method has a flaky shape. Upon excitation with 280 nm UV light, all the CaGdAlO4： Eu^3＋ powders show bright red emission on account of the 4f-4f transitions of the Eu^3＋ ions. Moreover, the size of the phosphor particles and the emission intensity increase with the increase of calcined temperature. At the same calcination temperature of 1400 ℃, the ^5D0→^7F2 emission intensity of the sample prepared by HDW method is the highest. Stark components of the ^5D0→^7FJ emission transitions, both at room temperature and at a low temperature, reveal that the Eu^3＋ ions occupy only one site with non-centrosymmetry in the crystals.     

Synthesis and luminescence properties of Tb3+/Eu3+ co-doped GdAlO3 phosphors with enhanced red emission

The(Gd_(0.97-x)Eu_xTb_(0.03))AIO_3(x= 0.005-0.07) phosphors were synthesized by the co-precipitation method,using ammonium bicarbonate as a precipitant.The combined technologies of FT-IR,XRD,FESEM,PLE/PL and photo luminescence decay analysis were used to study the phase evolution,morphologies and luminescent properties.The phosphors with good dispersion exhibit strong vivid red emission located at 617 nm(~5 D_0-~7 F_2 transition of Eu~(3+)) under the optimal excitation wavelength of 275 nm(~4 f~8-4 f~75 d~1 transition of Tb~(3+),~8 S_(7/2)→6~I_J transition of Gd~(3+)).The presence of Gd~(3+) and Tb~(3+) excitation bands on the PLE spectra monitoring the Eu~(3+) emission directly gives an evidence of Tb~(3+) → Eu~(3+) and Gd~(3+) → Eu~(~(3+)) energy transfer,The emission intensity varies with the Eu~(3+) amount,and the quenching concentration is ～5 at% which is close to the calculated value.The quenching mechanism is determined to be the exchange reaction between Eu~(3+).The temperature-dependent PL analysis indicates that the best(Gd_(0.92)Eu_(0.05)Tb_(0.03))AlO_3 sample possesses good thermally stable properties.All the(Gd_(0.97-x)Eu_xTb_(0.03))AIO_3 phosphors in this work have similar CIE chromaticity coordinates and color temperatures,which are(0.65 ± 0.02,0.35 ± 0.02) and ～2558 K,respectively.Fluorescence decay analysis shows that the lifetime for～617 nm emission decreases with the content of Eu~(3+) and temperature increasing.Owing to the Tb~(3+)→ Eu~(3+) energy transfer,the luminescent properties of the(Gd_(0.92)Eu_(0.05)Tb_(0.03))AlO_3 phosphors are superior to the single Eu~(~(3+)) doped sample(Gd_(0.95)Eu_(0.05))AlO_3.As a result,the prepared phosphors may be widely used in solid-state display and light emitting devices.     

Luminescence properties of BaAl12O19:Tb,Ce and energy transfer between Ce3+, Tb3+

BaAl₁₂O₁₉:Tb,Ce phosphors were prepared by sol-gel technique, the crystalline structures of samples characterized by XRD, and the luminescence properties and energy transfer between Ce³⁺ and Tb³⁺ were investigated. The results indicated that the emission intensity and the excitation wavelength range of Tb³⁺ increased when Ce³⁺ was doped. It demonstrated that the Ce³⁺ added in the BaAl₁₂O₁₉:Tb could deliver energy to Tb³⁺, and Ce³⁺ was not luminous by itself. The relative emission intensity of Tb³⁺ at wavelength of 548 nm was the strongest by Tb³⁺/Ce³⁺ ratio of 2:1, when excited at 310 nm, which was the characteristic adsorption wavelength of Ce³⁺.     

Three-photon-excited fluorescence of Tb-doped CaO-Al2O3-SiO2 glass by femtosecond laser irradiation

A near infrared to visible blue, green, and red upconversion luminescence in a Tb^3＋-doped CaO-Al2O3-SiO2 glass was studied, which was excited using 800 nm femtosecond laser irradiation. The upconversion luminescence was attributed to ^5D3→^7F5, ^5D3→^7F4, ^5D3→^7F3, ^5D4→^7F6, ^5D4→^7F5, ^5D4→^7F4, and ^5D4→^7F3 transitions of Tb^3＋. The relationship between upconversion luminescence intensity and the pump power indicated that a three-photon simultaneous absorption process was dominant in this upconversion luminescence. The intense red, green, and blue upconversion luminescence of Tb^3＋-doped CaO-Al2O3-SiO2 glass may be potentially useful in developing three-dimensional display applications.     

Luminescent properties of β-Lu2Si2O7:RE(RE=Ce, Tb) nanoparticles by sol-gel method

Nanoscale RE³⁺ (RE=Ce, Tb) doped and codoped lutetium pyrosilicate Lu₂Si₂O₇ (LPS) phosphors were prepared by using the sol-gel method. Heat treatment was performed in the temperature range from 900 to 1100 °C. The crystal structure was analyzed by X-ray diffraction (XRD). The results showed that the β-type structure of LPS was obtained at 1100 °C. The excitation spectra in the UV and VUV ranges and the emission spectra of the samples were measured at room temperature, and their luminescent properties were studied. The energy transfer from Ce³⁺ to Tb³⁺ in the codoped samples were observed and discussed.     

Preparation and luminescent properties of MgTiO3：Eu3＋ phosphor for white LEDs

A novel red phosphor Eu3+ doped magnesium titanate (MgTiO3) was synthesized via sol-gel method. The X-ray diffraction patterns (XRD) revealed that a pure MgTiO3 phase was obtained. Its excitation spectrum consisted of a broad band (<350nm) and a series of narrow bands in the long wavelength, and the strongest excitation peak at 465nm might be exited by GaN-chip to emit red light for white LED. The phosphors showed strong emission at 614nm which could be attributed to the 5D0→7F2 emission of Eu3+ . The emission intensity of MgTiO3:Eu3+ phosphor reached the maximum at the Eu3+ concentration of 3.5mol.%. The luminescent properties (such as emission intensity and decay times) were further improved by introducing Al3+ as a charge compensator, demonstrating potential applications in white LED.     

Novel phosphors of Eu^3＋, Tb^3＋ or Tm^3＋ activated LaBGeO5

Rare earth borogermanates as a group of stable compounds provided various potential properties important for modern sciences. Among the properties of interests, luminescence was manifested due to the variability of rare earth elements and the compounds constituted an important group of potential candidate. In this work, novel phosphors of Eu³⁺, Tb³⁺ or Tm³⁺ doped LaBGeO₅ with the stillwellite type structure were synthesized by the solid state reaction method. Their X-ray and UV excitation luminescent properties showed that LaBGeO₅ was an excellent host lattice for the luminescence of Eu³⁺, Tb³⁺ and Tm³⁺. The LaBGeO₅:Eu³⁺, LaBGeO₅:Tb³⁺ and LaBGeO₅:Tm³⁺ presented bright red, green and blue emission light for both UV and X-ray excitation.     

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.     

Synthesis, crystal structure and fluorescence of a new europium complex with 2-bromobenzoate and 2,2′-bipyridine

A new complex of {[Eu2(2-BrBA)6(2,2'-bpy)2]2.CH3CH2OH·H2O} (2-BrBA=2-bromobenzoate; 2,2'-bpy=2,2'-bipyridine) was prepared by solvent method and characterized with X-ray single-crystal diffraction, IR spectroscopy, UV spectrscopy, and fluorescence spectroscopy. The complex crystallized in triclinic crystal system, PT space group, with a=1.17196(4) nm, b=-2.36142(9) nm, c=2.59151(9) nm, a=113.266(2)°, β=101.100(2)°, and γ=94.400(2)°. Two independent dinuclear molecules were contained in the asymmetric unit. The two molecules were similar to each other. Each Eu(Ⅲ) ion was nine-coordinated with seven oxygen atoms from five 2-BrBA ligands and two ni-trogen atoms from 2,2'-bpy molecule. The carboxylate groups acted as bidentate-chelating, bidentate-bridging and chelating-bridging coor-dination modes. The complex adopted a distorted monocapped square-antiprism coordination geometry. Five peaks at 579, 591, 613, 652,and 697 nm appeared in the fluorescence spectrum, corresponding to 5D0→7F0, 5D0→7F1, 5D0→7F2, 5D0→7F3, and 5D0→7F4 transition emis-sions of the Eu(Ⅲ) ion, respectively.     

Zirconium metal organic framework for design of tetragonal rare earth-doped zirconia nanoparticles

Zirconium metal–organic frameworks ZrOBDC (where BDC = C₆H₄(COOH)₂, terephthalic acid) doped and co-doped with rare earth ions Ln (ZrOBDC:Ln³⁺, where Ln³⁺ = Eu³⁺ and Tb³⁺ as well as Er³⁺ and Yb³⁺) were used as precursors for the design of tetragonal rare earth doped zirconia nanoparticles (t-ZrO₂:Ln³⁺ NPs) through annealing process. Preparation, characterization and luminescence properties of ZrOBDC:Ln³⁺ and ZrO₂:Ln³⁺ NPs were investigated. The as-obtained t-ZrO₂:Ln³⁺ NPs have high purity with an average size of 20–30 nm. The luminescence spectra of ZrOBDC:Tb³⁺ and ZrOBDC:Eu³⁺ display strong green and red emission at around 544 and 611 nm which correspond to ⁵D₄ → ⁷F₅ and ⁵D₀ → ⁷F₂ transitions of Tb³⁺ and Eu³⁺ ions, respectively. The green and red up-conversion emissions of ZrO₂:Er³⁺,Yb³⁺ NPs due to ²H_11/2, ⁴S_3/2 → ⁴I_15/2 and ⁴F_9/2 → ⁴I_15/2 transitions of the Er³⁺ ions are observed under 976 nm laser excitation.     

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.     

Physicochemical properties of Li3Ba2La3(MoO4)8:Eu,Tb red-emitting phosphor for solid state white lamps

In this work,combustion synthesis was used for the first time to fabricate a phosphor material with red emission for applications in solid-state white-light lamps.We synthesized a material with emission wavelength at λ_em=617 nm,excited under long UV-blue wavelength based on Eu³⁺,Tb³⁺-activated molybdates Li₃Ba₂(La_1-x-yEu_xTb_y)₃(MoO₄)₈ with 0 ≤ x ≤1 and 0 ≤ y ≤ 1.A series of pow...     

Tunable emission,energy transfer and thermal stability of Ce3+, Tb3+ co-doped Na2BaCa(PO4)2 phosphors

A series of single Ce³⁺ doped and Ce³⁺ and Tb³⁺ co-doped Na₂BaCa(PO₄)₂ (NBCP) phosphors was synthesized by conventional solid-stated reaction method. The crystal structure, luminescence properties, thermal stability and energy transfer were carefully investigated. Ce³⁺ is inferred to substitute the Ba²⁺ site in NBCP lattice. The color-tunable emission from blue to green is observed by adjusting Tb³⁺ concentration among NBCP:0.03Ce³⁺,yTb³⁺ phosphors. The energy transfer behavior from Ce³⁺ to Tb³⁺ ions is both illustrated by co-doped PL spectra and decay curves. The energy transfer efficiency is as high as 91.5%. The mechanism of energy transfer is resonance type of dipole-dipole transition. In this work, the optimal phosphor exhibits the excellent thermal stability which keeps at 94.9% of that initial value at room temperature when temperature reaches to 150 °C. The Ce³⁺ and Tb³⁺ co-doped NBCP phosphor is a promising candidate for the application in the general lighting and display fields.     

Characterization of Y2O2S： Eu^3＋, Mg^2＋, Ti^4＋ Long-Lasting Phosphor Synthesized by Flux Method

Long-lasting phosphor Y₂O₂S: Eu³⁺, Mg²⁺, Ti⁴⁺ was synthesized by a flux method and their luminescence properties were investigated. The result indicates that the unit cell parameter c is linearly increased with the increase of Eu₂O₃ content in Y₂O₂S: Eu_x³⁺ (0.01 ≤ x ≤ 0.10). On the other hand, the change of unit cell parameter a is not linear dependence. In the Y₂O₂S: Eu³⁺ crystal structure, Eu³⁺ ions only replaced Y³⁺ ions' places in which it posited center position of c axis. With the increase of Eu₂O₃ content, the position of the strongest emission peak changed from 540 nm (⁵D₁→⁷F₂ transition) to 626 nm (⁵D₀→⁷F₂ transition), and the maximum intensity was obtained when x = 0.09 in Y₂O₂S: Eu_x³⁺ (0.01 ≤ x ≤ 0.10). This is due to the environment of trivalent europium in the crystal structure of Y₂O₂S. Doping with Mg²⁺ or Ti⁴⁺ ions alone cannot get the good long-lasting afterglow effect, whereas co-doping with Mg²⁺ and Ti⁴⁺ ions and excited with 365 nm ultraviolet light, a strong thermoluminesence peak appeared, red and orange long-lasting phosphorescence (LLP) was also observed and the phosphorescence lasted nearly 3 h in the light perception of the dark-adapted human eye (0.32 mcd · m⁻²). Thus the LLP mechanism was analyzed.     

Luminescence Properties of Green-Emitting Phosphor （Ba1- x, Srx ） 2 SiO4 ： EU^2＋ for White LEDS

The （Ba1- x, Srx ） 2 SiO4 ： EU^2＋ green-emitting phosphors were synthesized by conventional solid-state reaction in a CO-reductive atmosphere, and their luminescent properties were investigated. The XRD data show that the Ba/Sr ratio not only affects the lattice parameters, but also influences the emission peak. The excitation spectra indicate that this phosphor can be effectively excited by UV light from 370 to 470 nm. The emission band is due to the 4f^65d^1→4f^7 transition of the Eu^2＋ ion. With an increase in x, the emission band shifts to longer wavelength and the reason was discussed. The emission spectra exhibit a satisfactory green performance under different excitation wavelength（380,398,412,420,460 nm）. （Ba1- x, Srx ） 2 SiO4 ： EU^2＋ is a promising phosphor for green white-lighting-emission diode by ultraviolet chip.     

Tunable emission properties of tri-doped Ca_9LiY_(2/3)(PO_4)_7:Ce~(3+),Tb~(3+),Mn~(2+) phosphors with warm white emitting based on energy transfer

Tri-doped Ca_9 LiY_(2/3)(PO_4)_7:Ce~(3+),Tb~(3+),Mn~(2+)phosphors were prepared by a high-temperature solid state method.Under UV light excitation,Ca_9 LiY_(2/3)(PO_4)_7:Ce~(3+)samples exhibit a broad band ranging from 320 to 500 nm.At 77 K,the emission spectra of Ca_9 LiY_(2/3)(PO_4)7:Ce~(3+)samples present two obvious emission peaks,indicating that Ce~(3+)ions occupy two different kinds of lattice sites(Ca(1/2) and Ca(3)),As a good sensitizer for Tb~(3+),Ce~(3+)ions in Ca_9 LiY_(2/3)(PO_4)_7 lattice can effectively transfer part of energy to Tb~(3+),and the energy trans fer mechanism is determined to be dipole-dipole interaction.Consequently,the emitting color for Ce~(3+) and Tb~(3+) co-doped Ca_9 LiY_(2/3)(PO_4)_7 samples can be tuned from bluish violet to green.In order to further enlarge the emission gamut,Mn~(2+)ions as red emission components were added,forming tri-doped single-phase Ca_9 LiY_(2/3)(PO_4)_7:Ce~(3+),Tb~(3+),Mn~(2+)phosphors.The Ca_9 LiY_(2/3)(PO_4)_7:Ce~(3+),Tb~(3+),Mn~(2+)phosphors exhibit tunable emission properties through controlling the relative doping concentration of Ce~(3+),Tb~(3+)and Mn~(2+).Especially,Ca_9 LiY_(2/3)(PO_4)_7:0.09 Ce~(3+),0.12 Tb~(3+),0.30 Mn~(2+)can emit warm white light.The sample shows good thermal stability.At 150℃,the emission intensity for Ce~(3+)(360 nm),Tb~(3+)(545 nm) and Mn~(2+)(655 nm) decreases to 63%,69%,and 72% of its initial intensity,respectively.Moreover,the sample obtains good stability after 10 cycles between room temperature and150℃.