Phosphor powders elaborated by spray-pyrolysis: Characterizations and possible applications (original) (raw)
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Moldavian Journal of the …, 2009
Yttrium tantalate, yttrium niobium-tantalate, and yttrium niobate doubly doped by Eu 3+ and Tb 3+ were investigated using X-ray diffraction and X-ray excitation luminescence in order to study their structural and luminescent properties. By means of X-ray diffraction, the crystallographic data for YTaO 4, Y(TaNb)O 4 , and YNbO 4 with double activation by Eu 3+ and Tb 3+ was first calculated. Under X-ray excitation luminescence, the rare earth emission centers can contribute to the overall luminescence. The simultaneous incorporation of Eu 3+ and Tb 3+ ions could permit us to obtain different luminescence colors on the entire visible spectrum. Due to their various luminescence chromaticities, the proposed rare earth activated phosphors are promising materials for optoelectronics as well as for X-ray intensifying screens for medical diagnosis providing the broad variation of photoluminescence colors from blue-to-green to yellow-to-red.
The Journal of Physical Chemistry C, 2010
Borate phosphors, with formulations Y 0.95 Eu 0.05 BO 3 (YBEu), Y 0.95 Tb 0.05 BO 3 (YBTb), Y 0.57 Gd 0.38 Eu 0.05 BO 3 (Y6G4BEu), and Y 0.57 Gd 0.38 Tb 0.05 BO 3 (Y6G4BTb) have been synthesized by spray pyrolysis at the maximum temperature of 700°C, and then annealed at 1200°C. The yttrium oxide-doped phosphor Y 0.95 Eu 0.05 O 1.5 (YOEu) was obtained by the same experimental conditions. The UV-VUV excitation spectra of the samples were recorded using synchrotron radiation. The emission intensities of these phosphors have also been investigated as a function of plasma gas pressure in a dedicated experimental setup. The intensities in the emission spectra were integrated, to compare the relative efficiencies of the phosphors. All phosphors were more efficient with increasing gas pressure in the plasma chamber. The emission intensity of YOEu was similar to that of YBEu or Y6G4BEu at low Ne-Xe pressure, but stronger at high pressure. For both lanthanide activators, the mixed borates Y6G4B and the pure YBO 3 (YB) have about same luminescence efficiency at low pressure, but the Y6G4B are better matrices than YB at high Ne-Xe pressure. With the introduction of Gd 3+ in the borates, the emission intensity is enhanced due to a better spectral overlap with the plasma emission at 173 nm, and also the occurrence of multiple energy transfers between Gd 3+ ions before transfer to the emitter Eu 3+ or Tb 3+ . A "color effect" with the variation of pressure in the plasma chamber is observed for the Eu 3+ -doped phosphors. The orange:red intensity ratio (i.e., 5 D 0 f 7 F 0,1 (560-600 nm)/ 5 D 0 f 7 F 2 (600-640 nm)) increases as the gas pressure is raised. This observation is related to the spectral changes occurring in the plasma, and it is corroborated by the observation of selective excitation in the VUV range of Eu 3+ at C i versus C 1 crystallographic sites.
Photoluminescence Properties of Nanocrystalline YBO3: EU3+ Phosphor
2015
Nanoscale phosphors show superior performance characteristics than the bulk phosphors. This paper explains the synthesis of nanocrystalline YBO3 doped with rare earth element Europium by modified combustion method. The sample was characterized by X-ray Diffraction (XRD), Field Effect Scanning Electron Microscopy (FESEM), and Photoluminescence (PL) properties. Diffractogram showed the nanocrystalline nature of as prepared sample. FESEM image confirmed the XRD result. Photoluminescence emission spectra showed strong red emission peak at 613 nm. The colour coordinates of the as prepared sample match fairly with standard CIE colour coordinates for red colour. Thus, YBO3 doped with Eu3+ nanophosphor is a potential candidate for tricolor lamps and optical devices.
Luminescence and structural properties of Y(Ta,Nb)O 4:Eu 3+,Tb 3+ phosphors
Materials Chemistry and Physics, 2010
Yttrium tantalate (YTaO 4 ), yttrium niobium-tantalate (YTaNbO 4 ) and yttrium niobate (YNbO 4 ) doubly doped by Eu 3+ and Tb 3+ , were investigated using X-ray diffraction and X-ray excitation luminescence in order to study their structural and luminescent properties. By means of X-ray diffraction, the crystallographic data for YTaO 4 and YNbO 4 with double activation by Eu 3+ and Tb 3+ were first calculated. Under X-ray excitation luminescence, the rare earth emission centers contribute to the overall luminescence. Due to their various luminescence chromaticities, the proposed rare earth activated phosphors are promising materials for optoelectronics as well as for X-ray intensifying screens for medical diagnosis providing the broad variation of visible photoluminescence from blue to red.
Research on Chemical Intermediates, 2014
The present paper reports the synthesis, photoluminescence (PL), and thermoluminescence (TL) studies of Eu 3?-doped yttrium oxide (Y 2 O 3) phosphor using inorganic materials like Y 2 O 3 , flux calcium fluoride, and europium oxide. The sample was prepared by the modified solid state reaction method, which is the most suitable for large-scale production. The prepared phosphor sample was characterized using powder X-ray diffraction, field emission gun scanning electron microscopy, high resolution transmission electron microscopy, Fourier transform infrared spectroscopy , PL, TL, and Commission Internationale de I'Eclairage techniques. The PL emission was observed in the range 417-632 nm ranges all visible regions for the Y 2 O 3 phosphor doped with Eu 3?. Excitation spectrum found at 254 nm. Sharp intense peaks found around 467, 534, 594, 612, and 632 nm with high intensity. From the XRD data, using the Scherer's formula, the calculated average crystallite size of Eu 3?doped Y 2 O 3 phosphor is around 45 nm. TL study was carried out for the phosphor with UV irradiation. The present phosphor can act as single host for white light emission in display devices.
Journal of Electronic Materials, 2017
Red-emitting Eu 3+-doped (Y,Gd)BO 3 phosphors have been synthesized by a sol-gel process using metal oxides and boric acid as starting materials and citric acid as chelating agent. The main factors affecting the structure and luminescence properties of the product, such as sintering temperature, chemical composition, and Eu 3+ doping concentration, were investigated. X-ray diffraction (XRD) analysis indicated that the phosphors begin to crystallize at sintering temperature of 700°C and become phase pure at 900°C. The average size of the phosphor particles after sintering at 1000°C was determined to be about 30 nm to 50 nm. The (Y,Gd)BO 3 :Eu 3+ phosphors were found to exhibit strong red emission at 611 nm and 625 nm corresponding to the 5 D 0-7 F 2 transitions of Eu 3+ in the host lattice. The photoluminescence intensity was enhanced by posttreatment at 900°C and remained unchanged at 1000°C. It was also found that the optimal concentration of Gd 3+ ions for Eu 3+ emission was 35%, and no concentration quenching of the photoluminescence was observed even at Eu 3+ doping concentration up to 30%.
Journal of Luminescence, 2012
This paper reports the luminescence emission spectra of Y(Ta,Nb)O 4 activated by rare earth ions such as Eu 3 þ and Tb 3 þ. The influence of these rare earth ions on the luminescence of yttrium niobiumtantalate phosphors was investigated. The luminescent properties were studied under X-ray and electron beam excitations. Under these excitations, the emission centers of the rare earth activators (Eu 3 þ ,Tb 3 þ) were found to contribute efficiently to the overall luminescence. Changing the mol concentration of the incorporated activators resulted in a broad variation of visible photoluminescence. Color cathodoluminescence images showed clearly the dependence of chromaticity on the different activators. With their various luminescence chromaticities, these rare earth activated phosphors are promising materials for solid-state lighting applications as well as for X-ray intensifying screens in medical diagnosis, providing a broad variation of visible photoluminescence from blue to red.
Luminescence and luminescence quenching of highly efficient Y2Mo4O15:Eu3+ phosphors and ceramics
Scientific Reports, 2016
A good LED phosphor must possess strong enough absorption, high quantum yields, colour purity, and quenching temperatures. Our synthesized Y 2 Mo 4 O 15 :Eu 3+ phosphors possess all of these properties. Excitation of these materials with near-UV or blue radiation yields bright red emission and the colour coordinates are relatively stable upon temperature increase. Furthermore, samples doped with 50% Eu 3+ showed quantum yields up to 85%, what is suitable for commercial application. Temperature dependent emission spectra revealed that heavily Eu 3+ doped phosphors possess stable emission up to 400 K and lose half of the efficiency only at 515 K. In addition, ceramic disks of Y 2 Mo 4 O 15 :75%Eu 3+ phosphor with thickness of 0.71 and 0.98 mm were prepared and it turned out that they efficiently convert radiation of 375 and 400 nm LEDs to the red light, whereas combination with 455 nm LED yields purple colour. Solid state light sources based on the blue emitting InGaN semiconductor chips became a revolution in lighting industry after the discovery of efficient blue emitting diode by S. Nakamura in 1991 1. However, the blend of the blue light emitted by diode and yellow emitted by a Y 3 Al 5 O 12 :Ce 3+ (YAG:Ce) phosphor usually yields a cold white light due to deficiency of the red component in the spectrum. To overcome this issue some red phosphors are added to the light source. Frequently used nitride based red phosphors are very expensive and require complicated synthesis techniques. Another way to produce solid state white light sources is to employ near UV emitting LED chip and coat it with red, green and blue phosphor. The advantage of such approach is much broader phosphor selection than for blue LED excitation. Inorganic materials doped with rare earth ions are mostly used as activators in the mentioned phosphors. Since there are some efficient blue (BaMgAl 10 O 17 :Eu 2+) and green (SrSi 2 O 2 N 2 :Eu 2+ , Ba 2 SiO 4 :Eu 2+) 2,3 phosphors, the main problems arise with finding a suitable and relatively inexpensive red-emitting phosphor. Moreover, the requirements for LED phosphors are also high, for instance, strong absorption of LED radiation, high thermal quenching temperature, high quantum yield, excellent chemical and thermal stability and absence of emission saturation at high fluxes 4. Unfortunately, it is very hard to find materials that meet all the aforementioned criteria and, therefore, the reports of efficient Eu 3+ doped phosphors with high thermal stability is scarce. Trivalent europium doped materials are usually considered as good red-emitting phosphor candidates for LEDs. On the other hand, Eu 3+ ions typically possess rather low absorption strength due to the spin and parity forbidden nature of their intraconfigurational [Xe]4f 6 → [Xe]4f 6 transitions 5. However, in molybdates, tungstates, niobates and vanadates these transitions, especially at shorter wavelengths (< 400 nm), become rather strong due to admixing with low lying charge transfer (CT) band 6-8. The position of the CT band depends on the host material as do the emission spectra of Eu 3+ ions. Thus by selecting the appropriate host material one should be able to obtain a desired absorption strength and emission profile.
Studies concerning the properties of some europium activated phosphors based on yttrium tantalate
Physics Procedia, 2009
Rare earth activated YTaO 4 based phosphors are perspective materials for optoelectronics. The paper presents some physical and chemical aspects related to the influence of the host lattice composition and crystalline order on the luminescence of rare earth ions. In this respect, Eu -activated Y(Ta, Nb)O 4 powders have been prepared by solid state reaction, from homogeneous mixtures consisting of oxide precursors and flux. Photoluminescence (PL) spectroscopy, X-ray diffraction, FTIR spectroscopy and SEM have been used to investigate the structural and luminescent properties of Y(Ta,Nb)O 4 : Eu phosphors. Attempts has been made at establishing a correlation between the morphostructural parameters of the host lattice containing variable niobium amount and the PL properties. The interaction between the tantalate-niobate matrix and the Eu-emission centres is considered in correlation with the PL characteristics.
Sensitization Effect of Yb3+ in Upconversion Luminescence of Eu3+ Codoped Y2O3 Phosphor
The rare earths (RE) doped luminescent materials have been the subject of significant interest in recent years due to their potential applications in different fields . In these materials, mainly the rare earth elements are responsible for the generation of radiation of light of different color by changing the dopants, which are useful for various applications . Several oxide host materials are available for the preparation of rare earth doped luminescent materials, but the Y 2 O 3 is chosen due to their high optical band gap, low phonon frequency and ionic radii comparable with most of the rare earths. Several studies have been reported on synthesis and optical characterisation of nanocrystalline Eu 3+ doped phosphors . But, the upconversion (UC) emission with NIR excitation in singly Eu 3+ doped materials is not possible. So, in order to get visible UC emission from Eu 3+ ion, another rare earth ion can be used as sensitizer to excite Eu 3+ ions. In our previous study, we have excited Eu 3+ ion by a 980 nm laser using Er 3+ as sensitizer and studied its UC behavior . In most of the cases, Yb 3+ ion is taken as the sensitizer because of its higher absorption crosssection corresponding to 980 nm excitation.