Temperature dependence of red emission in YPO4:Pr3+ nanopowders

In order to compare spectroscopic properties between nanosized and that in single crystal form of YPO4:Pr3+, temperature-dependence of the red emission from 3P0 → 3H4 and 1D2 → 3H4 transitions of YPO4:0.1 at. % Pr3+ nanopowders has been investigated in details. The emission spectra of the sample in size of 20 nm, under selective excitation at 3P2, measured at different temperatures, T = 10, 100, 200 and 300 K have been recorded. The variation of emission intensity of each 3P0 → 3H4 and 1D2 → 3H4 against temperature has been investigated. Several spectral lines constitute 1D2 → 3H4 emission, assigned to transitions between 1D2 and 3H4 Stark levels are observed with no noticeable shifts between them and those observed at the single crystal. It is found that 1D2 → 3H4 emission intensity dominates that of 3P0 → 3H4 transition, pointing out the high efficiency of the multiphonon relaxation (MPR) process from 3P0 to 1D2. Fitting the temperature dependence of 3P0 → 3H4 emission intensity permits to estimate the phonons and their energies involved in non-radiatively transition between 3P0 and 1D2 levels, which are found different from single crystal. Also, fitting the multiphonon relaxation (MPR) rates against temperature, extracted from the measured 1D2 lifetime gives information that seven phonons can be involved to bridge the gap between 1D2 and 1G4. Furthermore, the possibility to use the YPO4: 0.1 at. % Pr3+ in the nano-thermometry application in temperature range T = 10–300 K was investigated

Photoluminescence properties of nano-sized (Lu1-xYx)PO4:Pr3+ (x = 10, 20, 30, 40, 50 at. %) phosphor powders

Herein we present the enhancement of photoluminescence properties of nano-sized LuPO4:Pr3+ phosphor powders synthesized by sol gel process with incorporation of yttrium ions inside of this single matrix to obtain (Lu1-xYx)PO4:Pr3+ (x = 10, 20, 30, 40, 50 at. %) powders. Under UV excitation at 270 nm the emission spectra of LuPO4:Pr3+ nanopowder do not present any characteristics emission band attributed to 4f15d1→4f2 transitions of Pr3+ ions, while a large emission band has been observed which due to defects created in LuPO4 cell by doping considering the ionic radius of Pr3+ is larger compared to the ionic radius of Lu3+, this band extinguishes gradually at the time insertion of the Y3+ ions until its total disappearance (for x = 40 at. %).It was found that the emission spectra of (Lu1-xYx)PO4:Pr3+ nanopowders under λex = 230 nm presents only the characteristics emission bands of Pr3+ ions with a remarkable influence of the rate of Y3+ ions on the intensity of this bands. Furthermore, it was observed that the improvement in the luminescence properties of (Lu1-xYx)PO4:Pr3+ nanopowders is very remarkable in visible range

Optical Properties of Blue Phosphor

LiIn1−Tm(WO4)2 (=0, 0.5, 1, 5, and 10 at.%) polycrystalline powders blue phosphors were prepared via the classical solid-state reaction method. X-ray diffraction (XRD), scanning electron microscope (SEM), photoluminescence excitation, and emission spectra were used to characterize LiIn1−Tm(WO4)2 phosphors. By analyzing the excitation and emission spectra of LiIn1−Tm(WO4)2 samples, the result indicates that there exists the energy transfer only from the WO42− group to the 1G4 energy level of Tm3+ ion. On the other hand, the influence of the thulium concentration on the blue emission transition 1D2→3F4 and 1G4→3H6 and the emission of WO42− group are investigated

Intra- and inter-configurational luminescence spectroscopy of Pr 3+ -doped YPO 4 nanophosphors

Nanopowders of YPO4 phosphors with different Pr3+ doping were successfully prepared by a sol gel method under different synthesis conditions. The crystallite size and strain show a strong dependence on the Pr3+ doping concentration and on the annealing temperature. By annealing at 300 degrees C one can obtain the xenotime structure of the pure YPO4. The crystallite size can be controlled by controlling the annealing temperature and it increases with increasing the annealing temperature. The room temperature inter-configurational 4f(2) 4f5d and intra-configurational 4f(2) 4f(2) emission-excitation transitions spectra are measured and investigated. Upon 4f(2) 4f(2) emission transitions and peaks in red region assigned to D-1(2) -> H-3(4) transition as photon cascade emission phenomena (PCE). The presence of only D-1(2) -> H-3(4) transition is discussed. In addition, the D-1(2) energy level lifetimes as well as the refractive indexes were determined and discussed

Sol gel synthesis and pH effect on the luminescent and structural properties of YPO4: Pr3+ nanophosphors

Pr3+-doped YPO4 nanophosphors prepared by simple sol gel method with different pH values (2, 4, 7 and 11) were obtained. The nanopowders samples were characterized by X-ray diffraction (XRD), room temperature steady and time resolved photoluminescence spectroscopy. The thorough study of pH influence on particles structure and luminescence of YPO4: 1 at. Pr3+ is presented. It was found that the grain size of samples increases with increases in pH value and obtained particles crystallize in a tetragonal phase with xenotime structure. Under 4f5d excitation (230 nm), all emission spectra show the inter -configurational 4f(2)- GT 4f5d and under (3)P2 excitation (449 nm), only the intra-configurational D-1(2)- GT H-3(4) red emission transition between 580 nm and 620 nm are observed. The highest luminescent intensity was obtained for samples prepared at pH = 4. Furthermore, it was found that the pH of solution has no effect of D-1(2) lifetime. (C) 2017 Elsevier B.V. All rights reserved

Annealing effect on the photoluminescence properties of Ce3+ doped YPO4 nanophosphors

This work explores the influence of annealing temperature on microstructural and optical characteristics of Ce 3+ - doped YPO 4 nanopowders prepared by sol gel method. Samples were annealed at various temperatures (T = 300, 500, 700, 900, 1050 °C), their structure, morphology, and photoluminescent properties were characterized by X-ray diffraction (XRD), Scanning electron microscopy (SEM), TGA-DTA analysis and Photoluminescence spectroscopy (PL). X-ray diffraction analyses confirmed their pure tetragonal zircon structure with average grain size from 5 nm up to 30 nm in dependence on the calcination temperature. The SEM image shows quasi-spherical agglomerated nanoparticles with no heterogenic size. Photoluminescence emission spectra of powders were recorded using excitation wavelength at 245 nm. We investigated the influence of annealing temperature on the optical properties, for samples annealed up to 700 °C no emission has been observed, but the emission increased with annealing temperature above 700° and the characteristic Ce 3+ emission bands (4f 1 →4f 0 5d 1 ) have been observed. Emission intensity increased with annealing temperature due to beter crystallinity and incorporation of Ce 3+ ions in Y 3+ site