Luminescent properties of Eu3+ activated tungstate based novel red-emitting phosphors (original) (raw)
Related papers
Journal of Luminescence, 2011
The correlation between the crystal structure and luminescent properties of Eu 3 þ -doped metal tungstate phosphors for white LEDs was investigated. Red-emitting A 4À 3x (WO 4 ) 2 :Eu x 3 þ (A¼ Li, Na, K) and B (4À 3x)/2 (WO 4 ) 2 :Eu x 3 þ (B¼ Mg, Ca, Sr) phosphors were synthesized by solid-state reactions. The findings confirmed that these phosphors exhibited a strong absorption in the near UV to green range, due to the intra-configurational 4f-4f electron transition of Eu 3 þ ions. The high doping concentration of Eu 3 þ enhanced the absorption of near UV light and red emission without any detectable concentration quenching. Based on the results of a Rietveld refinement, it was attributed to the unique crystal structure. In the crystal structure of the Eu 3 þ -doped metal tungstate phosphor, the critical energy transfer distance is larger than 5Å so that exchange interactions between Eu 3 þ ions would occur with difficulty, even at a high doping concentration. The energy transfer between Eu 3 þ ions, which causes a decrease in red emission with increasing concentration of Eu 3 þ , appears to be due to electric multi-polar interactions. In addition, the Eu-O distance in the host lattice affected the shape of emission spectrum by splitting of emission peak at the 5 D 0 -7 F 2 transition of Eu 3 þ .
Journal of Luminescence, 2008
The luminescence properties of Eu 3+ -and Sm 3+ -doped potassium tungstate phosphors were investigated. The K 4À3(x+y) (WO 4 ) 2 :Eu x 3+ ,Sm y 3+ phosphor was produced by solid-state reactions, followed by re-firing with a flux. The phosphor showed a strong absorption in the near-UV to green region due to 4f-4f electron transitions of the Eu 3+ and Sm 3+ ions, generating a red emission. The excitation spectrum could be adjusted by Sm 3+ -codoping. A small amount of Sm 3+ , acting as a sensitizer, increased the energy absorption peak at 405 nm. The crystal structure and local environment around the Eu 3+ ions were determined using the Rietveld method. The crystal structure of this phosphor was determined to be monoclinic with a space group of C2/c. The small Eu-0 distance in the crystal led to high energy-level splitting at the 5 D 0 -7 F 2 transition of the Eu 3+ ions, resulting in more emission peaks. Crown
Luminescence properties of lutetium based red-emitting phosphor NaLu(WO_4)_2:Eu^3+
Optical Materials Express, 2013
The compounds containing lutetium and tungsten atoms have large effective atomic number (Z eff ) and high stopping ability for high energy radiation because both lutetium and tungsten atoms are heavy with large atomic number. In order to obtain a new red-emitting phosphor with high efficiency for X-ray detection, the trivalent europium ion (Eu 3+ ) activated alkaline double tungstate phosphor NaLu(WO 4 ) 2 :Eu 3+ was prepared by high temperature solid state reaction. The crystalline structures of synthesized phosphor were determined by powder X-ray diffraction (XRD) and elucidated using Topas Academic software, and the morphologies were characterized by thermal field emission scanning electron microscopy (SEM) combined with energy-dispersive X-ray spectroscopy (EDS). The Rietveld structural refinement results suggest that the cell parameters become larger with the increasing of Eu 3+ doping concentration. The emission spectra of NaLu(WO 4 ) 2 :Eu 3+ under UV and Xray radiation were measured, respectively. It was observed that this microparticle phosphor shows intensive red emission under X-ray radiation, which implies that NaLu(WO 4 ) 2 :Eu 3+ phosphor has potential application for X-ray detection.
Synthesis and Photoluminescence Properties of Eu3+ Doped Double Perovskite Tungstate
The microcrystalline samples of double perovskite tungstates M3WO6 (M = Ca, Sr and Ba) doped with Eu3+ ion were synthesized by modified solid state reaction method. The phosphor materials were characterized by XRD, SEM and photoluminescence (PL) spectroscopy. The XRD result reveals the formation of well crystallized and phase pure microcrystalline phosphor samples. Both of the PL excitation and emission spectra of M3WO6:Eu3+ phosphors show very similar nature. The excitation spectra of characteristic yellow emission of Dy3+ ion show a broad CT band of (WO6)6- complex in UV region. The intense host absorption for characteristic yellow emission of Dy3+ ion indicates the effective energy transfer from tungstate host to Dy3+ ion. The energy transfer from (WO6)6- complex to Dy3+ ion is more efficient in Sr3WO6 than Ca3WO6 and Ba3WO6. The color of Dy3+ doped M3WO6 phosphors varies from orange to cyan color due to different yellow to blue intensity ratio.
Journal of Alloys and Compounds, 2010
We synthesized the Eu 3+ activated SrWO 4 nanocrystalline microspheres by a simple and facile synthesis route. X-ray diffraction patterns exhibited a unique phase of SrWO 4 :Eu 3+ scheelite structure with an average crystallite size of 58.9 nm. Fourier transform infrared spectra revealed the presence of absorption bands of WO 2− 4 and polyethylene glycol. The optical properties were investigated by varying the Eu 3+ ion concentration. Photoluminescence (PL) excitation spectra confirmed that these phosphors are able to be excited by UV, near UV, and visible wavelengths. PL emission spectra showed the bright-red emission due to the 5 D 0 → 7 F 2 electric dipole transition from the sites of non-inversion symmetry. The optimal doping concentration of Eu 3+ ions was found to be 7 mol%. Blending this phosphor with YAG:Ce 3+ phosphors may compensate their lack of a red spectral component, which leads to a good natural white light for indoor illumination.
Journal of The Electrochemical Society, 2008
We have investigated the luminescence of a series of M 5 Eu͑WO 4 ͒ 4−x ͑MoO 4 ͒ x ͑M = Li, Na, K͒ phosphors and discovered that Na 5 Eu͑WO 4 ͒ 4−x ͑MoO 4 ͒ x ͑0 Յ x Յ 4.0͒ exhibit the most intense red emission among the three investigated. Powder X-ray diffraction investigations show that a complete solid solution can be formed in the indicated composition range. The effect of chemical compositions on the luminescence properties of Na 5 Eu͑WO 4 ͒ 4−x ͑MoO 4 ͒ x has been investigated and discussed. The Commission International de l'Eclairage chromaticity coordinates were found to be ͑0.66,0.33͒ for Na 5 Eu͑WO 4 ͒ 4−x ͑MoO 4 ͒ x , which reaches the same level as that of the Y 2 O 2 S:Eu 3+ commodity. The color-rendering index ͑Ra͒ of a typical white-light-light emitting diode ͑WL-LED͒ based on Na 5 Eu͑WO 4 ͒ 2 ͑MoO 4 ͒ 2 was found to be 82.3, higher than that ͑i.e., Ra ϳ 70.8͒ obtained for the WL-LED fabricated using the commodity of La 2 O 2 S:Eu 3+ when the WL-LEDs were operated at a forward-bias current ͑I f ͒ of 20 mA at room temperature. Na 5 Eu͑WO 4 ͒ 4−x ͑MoO 4 ͒ x is therefore suggested to be a potential red-emitting phosphor for WL-LED.
Journal of Alloys and Compounds, 2012
Rare-earth ions doped inorganic luminescent materials (phosphors) in nanodimensions find widespread scientific and industrial applications. This paper report a novel red-emitting Eu 3+ doped Ba 3 Ca 3 (PO 4) 4 phosphors in nanodimensions were synthesized via one-step conventional solid state reaction method for first time at high temperature in air atmosphere. The morphology and nanostructures of synthesized phosphors were determined by powder X-ray diffraction (XRD), Field emission scanning electron microscopy (FE-SEM) and Energy-dispersive X-ray spectroscopy (EDS). The XRD observation reveals that the undoped and Eu 3+ doped Ba 3 Ca 3 (PO 4) 4 phosphors are in single crystalline phase with the sizes of 40-65 nm. FE-SEM image indicated the phosphor is composed of nearly spherical particles and rod like structures with several nanometer sizes. The presence of orthophosphates in Ba 3 Ca 3 (PO 4) 4 phosphor was identified by Fourier transform infrared (FT-IR) analysis and the thermal stability was studied by Differential scanning calorimetry (DSC). Diffuse reflectance spectra (DRS) evidenced the incorporated Eu 3+ ions in host material. In addition, the bandgap of these samples were estimated from the Mubelka-Munk function. The room-temperature photoluminescence spectra show the characteristic red fluorescence originating from intra 4f 5 D 0 ? 7 F 2 (616 nm) transition of Eu 3+ is observed by introducing Eu 3+ ions in Ba 3 Ca 3 (PO 4) 4 phosphors. The calculated color coordinates are lies in the orange-red region. Therefore, these obtained results suggest that the prepared phosphors exhibit great potential for use as red-component for near ultraviolet white light emitting diodes (NUV WLEDs).
Synthesis and Photoluminescence Properties of the High-Brightness EU3+
2017
Eu3+ doped red phosphors Li0.5Al0.5Mg2 (MoO4)3 were prepared by the combustion method, and their luminescent properties were studied. Under the excitation of nearUV 395 nm, the phosphors show intense red emission with the peaks located at 615 and 595 nm. The influence of Eu3+ concentration on the luminescent properties of Eu3+ doped Li0.5Al0.5Mg2(MoO4)3 was investigated and the 3% (mole fraction) was the appropriate molar concentration. By sintering Li0.5Al0.5Mg2(MoO4)3:xEu3+ phosphor at 750°C, PL intensity has a maximum value at 615 nm with Commision Internationale de I’Eclairage 1931 (CIE 1931) chromaticity coordinates (0.6616, 0.3336) . The phosphor could be suitable for the application of white light-emitting diodes.
Eu3+-activated potential red-emitting phosphor for solid-state lighting
Optik, 2017
The intense red-emitting NaCaY0.2Eu0.8(MoO4)3 phosphor was prepared by using a sol-gel method for the first time. Thermogravimetric-diferential thermal analysis, X-ray diffraction, field-emission scanning electron microscopy, FT-IR and luminescent measurements were used to characterize the NaCaY0.2Eu0.8(MoO4)3 particles. The resulting products obtained by using the sol-gel method have a narrower size distribution and a more regular particle shape than those obtained by using the solid-state reaction. The spectra analysis indicated that the obtained phosphor could be excited by UV light of 395 nm and visible light of 466 nm, also emits intense red light with a maximum at about 614 nm. The luminescent intensity of sol-gel derived is comparable with the solid state product and it is about 84 % of solid-state product under 395 nm light excitation. Comparative study with YAG:Ce and CaS:Eu 2+ phosphors, suggested that our synthesized phosphor can be used as an efficient red-emitting phosphor to compensate the red deficiency of YAG:Ce phosphor and also can serve as an alternative phosphor to replace sulfide based phosphors in the solid-state lighting applications.
Journal of the American Ceramic Society, 2018
A series of novel red-emitting Ca 8 ZnLa 1-x Eu x (PO 4) 7 phosphors were successfully synthesized using the high-temperature solid-state reaction method. The crystal structure, photoluminescence spectra, thermal stability and quantum efficiency of the phosphors were investigated as a function of Eu 3+ concentration. Detailed analysis of their structural properties revealed that all the phosphors could be assigned as whitlockite-type β-Ca 3 (PO 4) 2 structures. Both the PL emission spectra and decay curves suggest that emission intensity is largely dependent on Eu 3+ concentration, with no quenching as the Eu 3+ concentration approaches 100%. A dominant red emission band centered at 611nm indicates that Eu 3+ occupies a low symmetry sites within the Ca 8 ZnLa (PO 4) 7 host lattice, which was confirm by Judd-Ofelt theory. Ca 8 ZnLa 1-x Eu x (PO 4) 7 phosphors exhibited good color coordinates (0.6516, 0.3480), high color purity (∼96.3%) and high quantum efficiency (∼78%). Temperature-dependent emission spectra showed that the phosphors possessed good thermal stability. A white light-emitting diode (LED) device were fabricated by integrating a mixture of obtained phosphors, commercial green-emitting and blue-emitting phosphors into a near-ultraviolet LED chip. The fabricated white LED device emits glaring white light with high color rendering index (83.9) and proper correlated color temperature (5570 K). These results demonstrate that the Ca 8 ZnLa 1-x Eu x (PO 4) 7 phosphors are a promising candidate for solid state lighting.