Luminescent properties of LaAlO3:RE (RE = Eu3+, Tb 3+) prepared by microwave-assisted self-combustion method (original) (raw)
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Optical Materials, 2019
Stimulated luminescence of novel La 2 O 3 nanophosphors doped with Dy 3+ and Eu 3+ and co-activated with Li + , prepared by microwave-assisted solution combustion synthesis, was investigated for the very first time. X-ray diffraction results indicated hexagonal La 2 O 3 crystalline phase. Lanthanide and Li + doping did not affect the La 2 O 3 crystal structure. Scanning electron microscopy images showed nanoparticle morphologies such as plates, rods and irregular shapes. Photoluminescence spectra of La 2 O 3 :Dy 3+ , Li + exhibited blue and green emission bands due to Dy 3+ transitions. For La 2 O 3 :Eu 3+ , Li + , sharp emission lines, corresponding to the optical transitions of Eu 3+ were observed. Thermoluminescence glow curve of La 2 O 3 :Dy 3+ , Li + previously exposed to beta radiation exhibited a prominent glow peak located at ∼46 °C, possibly useful for after-glow or persistent lu-minescence applications, whereas La 2 O 3 :Eu 3+ , Li + curve, displayed three intense peaks at ∼50, ∼110 and ∼150 °C. Thermoluminescent signal repeatability and decay curve asymptotic behaviour could place La 2 O 3 :Eu 3+ , Li + as suitable for medium and high-dose radiation dosimetry applications.
Combustion synthesis and photoluminescence properties of LaAlO3 nanophosphors doped with Yb3+ ions
Journal of Luminescence, 2014
Ytterbium doped lanthanum aluminate (LaAlO 3 ) nanophosphors have been prepared by a combustion process with glycine as a fuel. The structures of the powders were determined by X-ray diffraction (XRD), the morphology of the annealed materials was observed using scanning electron microscopy (SEM), the average crystalline grain sizes have been determined by transmission electron microscopy (TEM) and photoluminescence properties using fluorescence spectroscopy. Pure LaAlO 3 phase was obtained at 800 1C heated for 4 h, with an average crystal size, as determined by TEM, of 60 nm. Emission spectra and decay times of main luminescence transitions were measured at room temperature. A strong emission is reported at 986 nm from the ( 2 F 5=2 -2 F 7=2 ) transition, whose intensity depends on Yb concentration.
Solid State Sciences, 2011
Europium-doped lanthanum aluminate (LaAlO 3 ) powder was prepared by using a combustion method. The crystallization, surface morphology, specific surface area and luminescence properties of the samples have been investigated. Photoluminescence studies of Eu doped LaAlO 3 showed orange-reddish emission due to Eu 3þ ions. LaAlO 3 :Eu 3þ exhibits one thermally stimulated luminescence (TSL) peak around 400 C. Room temperature electron spin resonance spectrum of irradiated phosphor appears to be a superposition of two centres. One of them (centre I) with principal g-value 2.017 is identified as an O À centre while centre II with an isotropic g-value 2.011 is assigned to an F þ centre (singly ionized oxygen vacancy). An additional defect centre observed during thermal annealing around 300 C grows with the annealing temperature. This centre (assigned to F þ centre) originates from an F-centre (oxygen vacancy with two electrons) and the F-centre along with the associated F þ centre appear to correlate with the observed TSL peak in LaAlO 3 :Eu 3þ phosphor. The activation energy for this peak has been determined to be 1.54 eV from TSL data.
Synthesis and luminescence properties of Eu 3+-doped LaAlO 3 nanocrystals
Journal of Alloys and Compounds, 2006
Eu 3+ /Dy 3+ ions co-doped Ca 2 La 8 (GeO 4 ) 6 O 2 (CLGO) phosphors were prepared by a pechini-type sol-gel method. The structural and morphological studies of the CLGO phosphors were carried out by measuring X-ray diffraction patterns and scanning electron microscope images. The photoluminescence (PL) spectra of the CLGO:Eu 3+ phosphor exhibited the intense red emission due to the electric-dipole transition while the CLGO:Dy 3+ phosphor showed the blue ( 4 F 9/2 ? 6 H 15/2 ) and yellow ( 4 F 9/2 ? 6 H 13/2 ) emissions with almost equal intensities. The Eu 3+ /Dy 3+ ions co-doped CLGO phosphor showed the improved white light by shifting towards the warm white region. The energy transfer from Dy 3+ to Eu 3+ ions was investigated by means of PL intensities. The lifetime measurements were also performed for single-doped and codoped samples. The calculated chromaticity coordinates indicated that these phosphors may be suitable for the fabrication of near-UV excitation-based white light-emitting diodes.
A B S T R A C T We synthesized the trivalent europium ions (Eu 3+) doped lanthanum aluminate (LaAlO 3 , LAO) nanophosphors by a solvothermal method. Their structural, morphological, and luminescent properties were systematically investigated. The obtained nanoparticles possessed single nanocrystallinity with a rhombohedral structure. For the excitation originating from the charge transfer band (O 2-to Eu 3+ ions) under 320 nm illumination, the featured emissions of Eu 3+ ions were detected in all the compounds. The optimum doping concentration of Eu 3+ ions in LAO was about 9 mol% and the concentration quenching was dominated by dipole-dipole interaction. Furthermore, the Judd-Ofelt (J-O) theory was used to estimate the J-O intensity parameters. Based on the temperature-dependent PL emission spectra, the thermal stability was analyzed and the activation energy was obtained to be 0.234 eV. Meanwhile, the decay time, color coordinate/purity, and cathodoluminescence behaviors of the synthesized nanophosphors were also studied. These characteristics make the Eu 3+-doped LAO nanoparticles a promising red-emitting phosphor for both ultraviolet-based white light-emitting diodes and field-emission displays.
Luminescence Characteristics of LaAlO3:Eu3+ Obtained by Modified Pechini’s Method
Open Journal of Synthesis Theory and Applications, 2017
The aim of the present work was to investigate the luminescent properties of europium-doped lanthanum aluminate (LaAlO 3) powder prepared by Modified Pechini (MP) method. Samples were prepared at different Eu 3+ concentrations and calcined at 1600˚C. Structural and morphology characterizations were obtained by X-ray diffraction (XRD), scanning electron microscopy (SEM), and transmission electron microscope (TEM). Luminescent properties were analyzed by photoluminescence (PL) and thermoluminescent phenomena. The XRD pattern shows pure lanthanum aluminate oxide LaAlO 3 with a rhombohedral structure. Photoluminescence studies of the powders was related to 4f → 4f(5 D 0 → 7 F i) (i = 1, 2, 3, 4) transitions of Eu 3+ ion, the most intense emission of Eu 3+ in LaAlO 3 was registered for the transition 5 D 0 → 7 F 1 , for 5% of Eu 3+. The recorded TL glow curves of excited samples showed a main TL peak, the main peak appeared its maximum as a function of excitation energy. The investigation demonstrates that polycrystalline LaAlO 3 :Eu 3+ powders calcined at 1600˚C have interesting luminescent characteristics.
Preparation and Optical Properties of La3PO7:Eu3+ Nanophosphors Synthesized by Combustion Method
MATERIALS TRANSACTIONS, 2020
Eu 3+ doped La 3 PO 7 nanoparticles were successfully synthesized under facial combustion method. The nano-phosphors then were characterized by some techniques including X-ray diffraction (XRD), scanning and transmission electron microscopy (SEM and TEM), photoluminescence spectrum (PL), and lifetime decay. SEM and TEM micrographs reveal exhibit of the La 3 PO 7 : Eu 3+ nanopowders in spherical morphology with an average size of about 20 nm, matching with Scherrer's formula calculation. Otherwise, the influence of annealing temperature and concentration of Eu 3+ ions on optical characteristics of Eu 3+ was doped La 3 PO 7 , and optical properties were investigated too. The photoluminescence shows the strong red emission originating from the 5 D 0 ¼ 7 F J (J = 1, 2, 3, and 4) transitions of Eu3+ and the 614 nm emission from the 5 D 0 ¼ 7 F 2 electronic dipole transition is dominant.
The concentration quenching of photoluminescence in Eu3+-doped La2O3
This work explores the influence of dopant concentration on photoluminescent emission and kinetics of Eu 3+ -doped (0.2−10 at.%) nanocrystalline lanthanumoxide powders. The X-ray diffraction analysis confirmed that all samples crystallize in La 2 O 3 hexagonal phase with space group P3m1. Transmission electron microscopy showed particles with non-uniform shape and diverse size distribution with an average particle size of (95 ± 5) nm. The room temperature photoluminescence spectra of all samples contain characteristic Eu 3+ luminescence lines with the most pronounced red 5 D 0 → 7 F 2 emission at about 626 nm. The maximum intensity of red emission is observed for the sample containing 5 at.% of Eu 3+ ions. The emission kinetics was recorded in the temperature range from 10 K to 300 K. The maximum lifetime value of 0.98 ms obtained for the sample with 0.5 at.% Eu 3+ at room temperature increases up to 1.3 ms at 10 K.
Eu3+ and Dy3+ doped La2MoO6 and La2Mo2O9 phosphors: Synthesis and luminescence properties
Materials Research Bulletin, 2020
We report a detailed structural analysis and properties of the photoluminescence (PL) and thermoluminescence (TL) spectra of Eu 3+ and Dy 3+ incorporated into novel La 2 MoO 6 and La 2 Mo 2 O 9 phosphors synthesized successfully through gel combustion synthesis. The formation of a tetragonal phase and a cubic structure were verified for La 2 MoO 6 and La 2 Mo 2 O 9 phosphors via X-ray diffraction (XRD) studies. Dy doped samples exhibited blue and green emissions at 480 nm (4 F 9/2 → 6 H 15/2) and 572 nm (4 F 9/2 → 6 H 13/2), and also Eu doped samples showed a sharp emission peaks at 612 and 619 nm (5 D 0 → 7 F 2) upon 349 nm pulse laser excitation. Peak shape (PS) technique was utilised to determine activation energy, frequency factor and order of kinetics associated with the main glow curves in undoped and Eu and Dy doped samples after X-ray irradiation. The present findings suggest that Eu and Dy incorporated La 2 MoO 6 and La 2 Mo 2 O 9 phosphors are highly auspicious candidates for applications in solid-state lighting.