Lutetium(III) cyclo­tetra­phosphate

Single crystals of the title compound, tetra­lutetium(III) tris­(cyclo­tetra­phosphate), Lu4(P4O12)3, were obtained by solid-state reaction. The cubic structure is isotypic with its AlIII and ScIII analogues and is built up from four-membered (P4O12)4− phosphate ring anions ( symmetry), isolated from each other and further linked through isolated LuO6 octa­hedra (.3. symmetry) via corner sharing. Each LuO6 octa­hedron is linked to six (P4O12)4− rings, while each (P4O12)4− ring is linked to eight LuO6 octa­hedra

Photoluminescence properties of CdSrP2O7:Eu2+CdSrP_2O_7:Eu^{2+} blue phosphor for white LED applications

Eu$^{2+}$-activated CdSrP$_2$O$_7$ phosphor was synthesized by conventional solid-state reaction. The photoluminescence properties of this phosphor were investigated by excitation and emission spectra UV–VUV region. It was found that the synthesized phosphor emitted broad blue emission band centered at 418 nm, with both 274 and 131 nm excitations. The temperature-dependence luminescence characteristic of CdSr$_{0.99}$P$_2$O$_7$:0.01Eu$^{2+}$ phosphor was reported, with the increase of temperature, the emission band exhibited blue shift and decreasing emission intensities. The phosphor CdSr$_{0.99}$P$_2$O$_7$:0.01Eu$^{2+}$ possesses good thermal stability. The activated energy was deduced to be 0.227 eV. These results indicated that CdSrP$_2$O$_7$:Eu$^{2+}$ phosphor could be a good candidate for near-UV based white light − emitting diodes (WLEDs)

Growth and Properties of Amorphous Erbium-doped Aluminum-yttrium Oxide Films Deposited by Aerosol-UV-Assisted MOCVD

International audienceErbium-doped yttrium-aluminum oxide films (Er:Y2O3-Al2O3) are deposited by aerosol-assisted metal-organic (AA-MO)CVD. The effects of the humidity of the carrier gas and UV assistance on their structure and optical properties during the deposition are investigated as a function of the substrate temperature and the aluminum mole fraction (Al2O3 mol.-%) in the liquid solution. The effect of substrate temperature is studied for a constant Al concentration of 33.33 mol.-% of Al-acac in the solution. The maximum deposition rates are reached under lower air humidity and with UV assistance in a surface temperature range between 350 and 460 °C. Nevertheless, as-deposited Er:Al2O3-Y2O3 films show a very low organic contamination when depositions take place under high air humidity and with UV assistance. The film composition is strongly dependent on air humidity, showing a very high aluminum content when working with a high humidity of the carrier gas, and yttrium-rich when working with a low humidity of the carrier gas. The refractive index of Er:Al2O3-Y2O3 films under these conditions is relatively high, reaching 1.76 when deposited at 460 °C.The effect of composition is studied at a substrate temperature of 410 °C. The effect on film composition when varying the aluminum mole fraction in the liquid solution is studied. The most influential parameter is the high air humidity, which induces stronger variation on the layer composition for the same liquid composition

Novel bluish white-emitting CdBaP2O7:Eu2+ phosphor for near-UV white-emitting diodes.

International audienceA new bluish white-emitting phosphor based on a phosphate host matrix, CdBaP2O7:Eu2+, was prepared by a conventional solid-state reaction method. The photoluminescence properties were investigated in both ultraviolet (UV) and vacuum ultraviolet (VUV) regions. The band-gaps of Eu-doped CdBaP2O7 powders can be tuned in the ranges of 2.26–2 eV. The Eu2+-doped CdBaP2O7 phosphor was efficiently excited at wavelengths of 250–400 nm, which is suitable for the blue emission band for near-UV light-emitting-diode (LED) chips (360–400 nm) and red emission peaks up to 700 nm. CdBaP2O7:Eu2+ displays two different luminescence centers, which were suggested to Ba2+ and Cd2+ sites in the host. The dependence of luminescence intensity on temperatures was measured. The chromaticity coordinates and activation energy for thermal quenching were reported. The phosphor shows a good thermal stability on temperature quenching

Structural and optical characterizations of rare earth pentaphosphates LnP5O14 (Ln 5 La, Gd) synthesized by the sol-gel process

International audienceThe sol-gel chemistry route has successfully been used to prepare samples of LnP5O14 (Ln = La, Gd) pentaphosphates from lanthanides chlorides and phosphorous pentoxide dissolved in isopropanol. Crystallized powders of single phase were obtained after calcination of gels at 350 °C. The structural characterizations of materials were investigated by means of X-ray diffraction as well as infrared and Raman spectroscopies, whereas their thermal behavior has been studied by differential thermal analyse and thermogravimetric analyses. Powders morphology was analyzed by means of scanning electron microscopy and laser granulometry. The photoluminescence properties of the Eu3+ ions in sol-gel derived LaP5O14 and GdP5O14 samples were investigated and compared with homologous samples synthesized by the conventional solid state reaction

Preparation and microstructural properties of erbium doped alumina-yttria oxide thin films deposited by aerosol MOCVD

International audienceAbstract Erbium-doped aluminum-yttrium oxide films (Er: Al2O3-Y2O3) were prepared by aerosol-UV assisted Metalorganic Chemical Vapor Deposition (MOCVD) at 410 °C and annealed at 1000 °C. The effects of humidity of carrier gas and UV-assistance on their structure and optical properties were investigated using scanning electron microscope, X-ray diffraction and Transmission electron microscopy. It was found that under low air humidity and without UV-assistance the films present a low mol% Al2O3 (10 mol%) two different structural phases are observed corresponding to the cubic and the monoclinic structures of Y2O3. When the deposition takes place under high air humidity and with UV assistance the Er:Al2O3-Y2O3 films present a very high mol% Al2O3 (88 mol%) and crystallize in the Y3Al5O12 (YAG) compound mixed with an amorphous phase. The Er3+ luminescence analyzed in the visible and IR regions, shows the classical green transitions. The best optical properties were obtained with the Er:Al2O3-Y2O3 films grown under high air humidity with UV-assistance. Under such deposition conditions, 4I13/2 lifetimes was found to be 1.1 ms. This indicates that the deposition conditions, in particular air humidity, play an important role in the luminescent properties even after annealing

Vacuum ultraviolet excited luminescence properties of sol–gel derived GdP5O14:Eu3+GdP_{5}O_{14}:Eu^{3+} powders

Sol–gel route has successfully been used to synthesize pure and Eu3+ doped polycrystalline samples of the GdP5O14 pentaphosphates. The as-prepared samples have structurally been characterized using X-ray diffraction. Optical properties in the vacuum ultraviolet (VUV) of Eu3+ activated GdP5O14 samples prepared either by sol–gel process or solid-state reaction were investigated at room temperature for comparison. In this GdP5O14 host matrix the P5O14 ultraphosphate groups were proved to exhibit an efficient absorption in the VUV range. The excitation spectra recorded in the VUV-UV spectral region from 120 nm to 350 nm have revealed the presence of Gd3+ 4f–5d interconfiguration transitions, Gd3+–O2− and Eu3+–O2− charge transfer states(CTS)in addition to intraconfiguration transitions of Gd3+ ions.Furthermore the Gd3+→Eu3+ energy transfer process was investigated and discussed in the framework of the multiphonon relaxation process. Besides, the GdP5O14:Eu3+ phosphor led to a strong red emission under 147/172 nm excitation, so that it can be considered as a promising red phosphor for mercury-free lamps and plasma display panels applications