Luminescence Properties Of Eu3 Research Articles

Luminescence properties of Eu2+, Gd3+ and Pr3+ doped translucent Sialon phosphors

Optical properties of hot pressed Sialon ceramics doped with different rare earth oxides (REOs) i.e. Eu2O3, Gd2O3, and Pr2O3 were investigated. The α-Sialon phase was the main phase obtained after sintering as observed by X-ray diffraction (XRD). The transparency of different samples of varying thickness measured from UV to IR region revealed that the samples were translucent in the visible region while transparent in IR region. The thin samples of 150 μm thickness had transmittance as high as 30% in the visible region. The luminescence was observed in transmittance mode to investigate the effect of sample thickness on luminescence intensity. We observed blue, yellow and red emissions in Sialon doped with Gd2O3, Eu2O3, and Pr2O3, respectively. The excitation wavelength for Gd2O3 and Pr2O3 doped samples were in UV region i.e. 280 and 270 nm, respectively, whereas, for Eu2O3 doped samples was in the blue region (460 nm). The Eu2O3 doped Sialon having 300 μm thickness showed better white light extraction as coupled with blue LED. Moreover, the fabricated phosphor samples exhibited high hardness around 20 GPa and fracture toughness above 5 MPa·m½.

Hydrothermal synthesis and luminescence properties of Eu2+-doped BaSiF6 microrods

Eu2+-doped BaSiF6 microrods with average diameter of 200nm, and length of 1–4μm were synthesized via a facile hydrothermal method. The crystal structure and morphology of final products were characterized by X-ray powder diffraction (XRD) and transmission electron microscope (TEM). Upon the excitation of 257nm UV light, the as-prepared samples exhibit strong and sharp line emission, which originates from the transitions within the 4f7 electron configuration of Eu2+ ions. The optimal doping concentration of Eu2+ ions in BaSiF6 matrix was confirmed to be about 15mol%.

Luminescent properties of Eu3+ doped NaY(WO4)2 nanophosphors prepared by molten salt method

Tetragonal phase NaY(WO4)2:Eu3+ phosphors were synthesized through a molten salt method. The X-ray powder diffraction (XRD) and field emission scanning electron microscopy (FE-SEM) were utilized to characterize the crystal structure and morphology. The emission and excited spectra were used to study the photoluminescence properties. The results of XRD and FE-SEM indicated that the samples prepared by this method were pure phase and the particle size was about 50 nm. The PL results showed that Eu3+5D0→7F2 red luminescence at 616.5 nm could be excited by 394.5 nm near-UV light and 465 nm blue light in NaY(WO4)2 host effectively, and the quenching concentration was 30 mol.%. The critical energy transfer distance and J-O parameters were calculated. The energy transfer type between Eu3+ was proved. What's more, the quantum efficiencies of the 5D0 level of Eu3+ were calculated as well.

Synthesis and luminescence properties of Eu2+- and Ce3+-doped AlONs

Series of Eu2+- and Ce3+-doped aluminium oxynitrides Al5O6N were prepared using the standard sol–gel technique with following firing in the flow of N2. Rare-earth metals oxides (Eu2O3 and CeO2) and complexes (Eu(acac)3 and Ce(acac)3) were used as sources of doping ions. It was found that both concentration of ions and nature of precursor affect phase composition and luminescent properties of Al5O6N:Eu2+ and Al5O6N:Ce3+ materials. At low concentrations of Eu2+ and Ce3+ the significant content of α-Al2O3 and AlN is observed and the content of impurities is higher for samples prepared from Eu/Ce(acac)3 comparing to samples prepared from oxides. The content of impurities decrease when the concentration of RE-ions increases to 0.1–0.2at%, at higher concentration the formation of RE-aluminates is observed. The intensity of luminescence increases when content of RE ions increases to 0.5at% for Al5O6N:Eu2+ and 0.1at% for Al5O6N:Ce3+, at higher concentrations a quenching of luminescence is observed.

Synthesis and study of Y2O3:Eu3+ nanoparticles

The synthesis method of weakly agglomerated Y2O3 powders based on the decomposition of metal–polymer gel (Pechini method) has been developed. The physicochemical properties of powders synthesized by the standard Pechini method and a method using foaming components have been compared. The luminescence properties of Eu3+-doped Y2O3 have also been studied.

Thermal, spectroscopic and luminescence investigations of lanthanide(III) coordination polymers based on V-shaped 4,4′-sulfonyldibenzoic acid

The complexes of lanthanide ions with V-shaped 4,4′-sulfonyldibenzoic acid (Hssdb) of the formula Ln2sdb3·nH2O, where Ln=La(III), Nd(III), Eu(III), Tb(III), Dy(III), Yb(III) and n=2–6 have been prepared by the hydrothermal method. The complexes were examined by elemental analysis, infrared spectroscopy (ATR-FTIR), X-ray diffraction pattern measurements and different methods of thermal analysis (TG-DSC and TG-FTIR). The luminescence properties of Eu(III) and Tb(III) complexes have been also investigated. The complexes crystallize in the triclinic (La, Nd and Eu) or monoclinic (Tb, Dy, Yb) crystal systems. Additionally, pentahydrate complexes of Dy(III) and Tb(III) are isostructural. 4,4′-sulfonyldibenzoate ligand coordinates lanthanide ions through both carboxylate groups. Heating of the complexes resulted in dehydration and formation of stable Ln2sdb3 compounds. Combustion of the organic ligand leads to the formation of intermediate stable lanthanide oxysulfate Ln2O2SO4 which further decompose into the suitable oxides. In nitrogen atmosphere, investigated complexes release: water, carbon oxides, disulphur oxide and benzene molecules. The Eu(III) and Tb(III) complexes exhibit characteristic red and green luminescence.

Syntheses and luminescence properties of EU(III) complexes with benzoic acid carboxymethyl ester derivatives

Benzoic acid carboxymethyl ester derivatives (BACED) with different substituents and their Eu(III) complexes (Eu(BACED)3(H2O)2) were synthesized, BACED being a bidentate ligand. The as-prepared complexes showed cloud flake aggregation structures with size in the range of 50–60nm. The luminescence spectra of the complexes indicated effective energy transfer from BACED to Eu3+. Three distinct peaks were observed in the excitation spectra of the Eu(III) complexes containing BACED and the as-prepared complexes exhibited effective emission when the wavelengths corresponding to these peaks were used as the excitation wavelengths. The longest luminescence lifetime of the as-prepared complexes was 1099.25µs and the best luminescent quantum efficiency was 59.21%. These results indicate that the Eu(III) complexes with BACED have excellent potential for use as luminescent materials.

Luminescent Properties of Eu3+-Activated Fluorogermanate Based Red Phosphor with High Thermal Stability

Luminescent Properties of Eu3+-Activated Fluorogermanate Based Red Phosphor with High Thermal Stability

Synthesis, characterization and luminescence properties of Eu3+-doped hydroxyapatite nanocrystal and the thermal treatment effects

In this work, we present the synthesis, characterization and the luminescence properties of Ca10(PO4)6(OH)2 (hydroxyapatite/HAp) nanocrystals doped with europium trivalent ions. The most important processes that lead to europium emissions in the visible region were identified. Eu:HAp nanopowder excited at 394nm (or 460nm) exhibits several emissions: (i) weak emissions at 579nm, 592nm and 616nm due to the 5D0→7F0, 5D0→7F1 and 5D0→7F2 transitions, respectively, with europium ion occupying site I in hydroxyapatite structure and (ii) strong emissions due to the 5D0→7F0 (574nm), 5D0→7F1 (602nm) and 5D0→7F2 (610–630nm) transitions, when Eu3+ is occupying site II. The emission spectrum and the time-resolved luminescence analysis showed that the HAp nanocrystals (nanopowder) thermally treated at temperature (T) between 500 and 800°C have a change in the initial Eu3+ site distribution of 100 % of Eu3+ at site I to a more stable one where the majority of europium ions are at site II: 30% remains at site I and 70% migrates to site II. In addition, an enhancement of the Eu3+ emission intensity is observed due to the increasing crystallite size. A time-resolved luminescence investigation using a short pulse laser excitation at 460nm was employed to measure the luminescence decays and to determine the most important mechanisms involved in the deexcitation process of 5D0 excited state of Eu3+, where it is seen a fast (2.9μs) energy transfer from Eu3+- site I (donor) to Eu3+- site II (acceptor) in the thermally treated nanopowders with T>500°C. The initial presence of 100% of Eu3+ at site I in the synthesized nanocrystals is gradually modified by the thermal treatments with temperatures above 500°C by thermal activation of Ca2+ vacancy (the charge compensator) diffusion through the HAp lattice, which propitiates the Ca2+- vacancies and Eu3+ ions to exchange positions in the lattice. By this thermal activated mechanism, Eu3+ ion migrates through the lattice until get the final distribution of 30% at site I and 70% at site II. As a result, the complete description of the Eu3+ (5D0) decay and the energy transfer process from Eu3+ (site I)→Eu3+ (site II) were proposed.

Luminescent properties of Eu3+-doped glass ceramics containing BaGdF5 nanocrystals under NUV-excitation for W-LEDs

Eu3+ doped transparent glass ceramics containing BaGdF5 nanocrystals were successfully fabricated by melt-quenching technique, and their structural and luminous properties were investigated. X-ray diffraction (XRD) and transmission electron microscopy(TEM) proved the existence of BaGdF5 nanocrystals in the transparent glass ceramics, which plays an important role in improvement the luminescent properties. The excitation spectra showed that the glass and glass ceramics could be effectively excited by near ultraviolet (NUV) light. Intense red emission located at 611nm and longer lifetimes observed in glass ceramics are attributed to the incorporation of Eu3+ ions into BaGdF5 nanocrystals with lower phonon energy. The CIE chromaticity coordinates of glass ceramics (GC610) were calculated as (x=0.625, y=0.374), which was close to the NTSC standard values for red (x=0.67, y=0.33). The results suggest that the glass ceramics may be used as potential red phosphors under near ultraviolet (NUV) light excitation for white light-emitting diodes (W-LEDs).

Luminescence properties of Eu3+-doped SiO2–LiYF4 glass–ceramic microrods

Photoluminescence properties of the glass–ceramics microrods containing Eu3+-doped LiYF4 nanocrystals have been studied and characterized. Judd–Ofelt parameters and quantum efficiency has been computed from luminescence spectra and discussed by comparison to the glass ceramic bulk and pellet. The radiative decay rate Arad is higher in the glass ceramic rods (221s−1) than in the glass ceramic bulk (130s−1) but the quantum efficiency computed is very low (21%) compared to the glass–ceramic bulk (97%). There are effective non-radiative decay channels that might be related to an influence of the dimensional constraints imposed by the membrane pores during xerogel formation and subsequent glass ceramization.

Luminescence Properties of Eu2+/Eu3+ Activated Barium Aluminate Phosphors with Gd3+ Concentration Variation

BaAl2O4:Eu2+/Eu3+ (1 mol %) co-doped with varying concentrations of Gd3+ (1, 2, 5 and 10 mol%) were prepared by combustion synthesis method at 600°C. All the compositions were investigated for their structural and photoluminescence properties. Samples prepared in open atmosphere showed the presence of both Eu3+ and Eu2+ states which indicates the reduction of Eu3+ to Eu2+ during the preparation of these compounds. The prepared materials at 600°C showed high intense broad peaks around 498 nm corresponding to Eu2+ and small peaks in the red region which are attributed to the presence of Eu3+. In the 1000°C annealed compounds, the intensity of the peak at 498 nm got increased. The intensity of this broad band for BaAl2O4:Eu2+/Eu3+(1 mol%):Gd3+(1 mol%) was three times than that of BaAl2O4:Eu2+/Eu3+(1 mol%). Thus second rare earth ion (Gd3+) acted as a good sensitizer and enhanced the photoluminescence intensity. The XRD spectra revealed the presence of hexagonal phase of BaAl2O4 as main phase and a small amount of a mixed phase Ba O! 6.6 Al2O3. Doping of Eu3+, Gd3+ did not change the crystalline structure of barium aluminate (BaAl2O4).

Synthesis and luminescence properties of Eu3+-doped KLa(MoO4)2 red-emitting phosphor

Eu3+-doped KLa(MoO4)2 phosphors were synthesized by a simple hydrothermal method. X-ray diffraction (XRD) analysis demonstrated that the as-prepared products were pure monoclinic phase of KLa(MoO4)2. Field emission scanning electron microscopy (FE-SEM) images indicated that the morphology of the prepared phosphors evolved from uniform spherical-like to irregular elliposid-like with increase of the concentration. The photoluminescence (PL) spectra displayed that the phosphors show strong red light around 618nm, attributed to 5D0→7F2 transition of Eu3+ ion under 465nm excitation, and the optimal Eu3+ doping concentration was about 15mol.% based on the concentration dependent emission spectra. According to Dexter’s theory the electric dipole–dipole interaction (D–D) is the main mechanism for energy transfer between Eu3+ and Eu3+ ions. The CIE chromaticity (x, y) of the phosphors were about (0.65, 0.35) and it is close to the standard red chromaticity of NTSC. Therefore, the phosphors could be used as red phosphors for white light-emitting diodes.

Structural and luminescent properties of Eu2+ and Nd3+-doped mixed alkaline earth aluminates prepared by the sol-gel method.

Alkaline earth aluminates with the overall nominal compositions Mg0.5Sr0.5Al2O4 (MSA), Ca0.5Mg0.5Al2O4 (CMA) and Ca0.5Sr0.5Al2O4 (CSA) doped with 0.5 mol% of Eu2+ and 0.25 mol% of Nd3+ ions were obtained by a modified aqueous sol-gel method and annealed in a reducing atmosphere at 900, 1000, 1100 and 1300 °C. The sample structures were investigated by XRD. Solid solubility was only confirmed for the CSA samples. UV-excited luminescence was observed in the blue region (λ = 440 nm) in the samples of CMA containing the monoclinic CaAl2O4 phase and in the green region (λ = 512 nm) in the samples of MSA containing hexagonal or monoclinic phases of SrAl2O4. The CSA samples, besides the blue region, exhibited an extended shoulder in the green region, which proved the existence of some pure strontium phases. Co-doped Nd3+ ions did not affect the wavelength of the emitted light, but the persistent luminescence at room temperature was greatly extended with respect to the aluminates doped with Eu2+ ions only.

Structural and Luminescence Properties of Eu<sup>3+</sup> and Dy<sup>3+</sup> Doped Magnesium Tellurite Borophosphate Ceramic

Lately, researchers have been considering the miscellaneous in the borophosphate crystalline’s luminescence as one of the important properties in hunt of the new functional material. In this study we discus the structural and luminescence properties of Eu3+/Dy3+ co-doped borophosphate ceramic. A series of ceramic samples based on B2O3-(65-)P2O5-25MgO-10TeO2 where (065) mol has successfully been prepared using solid state reaction method and sintered at 900°C. The crystalline phase of the powder samples was characterized using X-ray diffraction pattern. The diffraction patterns analysis indicated that the prepared samples were polycrystalline phase of B(PO4), Mg(PO3)2and Mg(BO3)(PO4). The local structure network structure has been investigated using Infrared Spectroscopy using KBr method. The FT-Infrared spectra reveal the presence of B-O-B vibrations, BO3 and BO4 bridging oxygen and P-O stretching modes of P-O-P, P=O and PO4 unit in the ceramics sample. Meanwhile, the luminescence properties of doped sample were measured based on analysis of emission spectra of photoluminescence spectroscopy. The emission peaks of Eu3+ doped sample were located at 593 nm, 613 nm, 652 nm, 685 nm due to the assigned transition 5D0-7FJ( J = 1, 2, 3, 4 ). The Dy3+ emission is due to 4F9/2 -5H15/2 and 4F9/2-6H13/2 transition. For Eu3+/Dy3+ co-doped sample consists of peaks belonging to the 4F9/2-6H15/2 (482 nm) and 4F9/2-6H13/2 (573 nm) transition while red emission 5D0-7F2 transitions appears at 611 nm. Improvement in the optical properties due to co-doping may be useful to discover a new highly efficient luminescent material that are very useful in optical devices and solid-state lighting.

Effects of thermal treatment on the structure and luminescent properties of Eu3+ doped SiO2–PMMA hybrid nanocomposites prepared by a sol–gel process

Hybrid nanocomposites are multifunctional materials and their properties are the consequence of molecular interaction between inorganic and organic phases. These materials are interesting hosts for lanthanide ions, such as Eu3+. The purpose of this research was to synthesize Eu3+ doped SiO2–PMMA hybrid nanocomposites by a sol–gel process and to study the effects of thermal treatment on the structure and luminescent properties of the material. Structural characterization was carried out using the FTIR, TG and 29Si NMR techniques, however, the luminescence studies were more sensitive to detect the slight structural changes resulting from the thermal treatment. The Eu3+ ions inserted into the matrix behaved as a structural probe and make it possible to notice the symmetry change from Eu3+ site, the decrease in the number of hydroxyl coordinated groups and the improvement in quantum efficiency as a result of the thermal treatment. In addition, the Judd–Ofelt intensity parameters were obtained and supported the interaction between the rare earth and hybrid material. The hybrid was obtained as a stable material until 200°C and the high sensitivity of the Eu3+ ions in the system may be used in future applications as thermal sensors, for example.

Metal–organic frameworks assembled from lanthanide and 2,5-pyridinedicaboxylate with cubane-like [Ln4(OH)4] building units

Lanthanide–organic frameworks based on 2,5-pyridinedicaboxylate (25p) ligand, formulated as [Yb4(OH)4(25p)4(H2O)3]·H2O (25pYb), [Y4(OH)4(25p)4(H2O)3]·H2O (25pY-1) and [Y6(OH)8(25p)5(H2O)2] (25pY-2), have been obtained as single phases under hydrothermal conditions. 25pYb and 25pY-1 are isostructural, and crystallize in the triclinic space group, P-1, with a=8.6075(5)Å, b=14.8478(7)Å, c=15.9164(9)Å, α=86.277(4)°, β=80.196(5)°, γ=81.785(4)°, and a=8.7166(6)Å, b=14.966(1)Å, c=15.966(1)Å, α=86.260(6)°, β=80.036(6)°, γ=81.599(6)°, respectively. 25pY-2 crystallizes in the monoclinic space group, P21/c, with a=24.9117(17)Å, b=13.7340(8)Å, c=14.3385(10)Å, β=100.551(7)°. 25pYb and 25pY-2 have been structurally characterized by single-crystal X-ray diffraction. The 25pYb structure is based on tetranuclear cubane-like [Yb4(OH)4]8+ clusters, which are interconnected to eight neighbouring clusters through teen surrounding 25p ligands leading to neutral 3D framework, while the structure of 25pY-2 is based on two independent cuban-like [Y4(OH)4]8+ clusters, which are joined together through Y1 cation leading to the formation of hexanuclear [Y6(OH)8]10+ clusters, which in turn are joined via Y2 cation resulting in infinite inorganic chain extending along c-axis, and each chain is interconnected to six adjacent chains through 25p ligands leading finally to 3D framework. The luminescence properties of Eu3+ and Tb3+ doped 25pY-1 and 25pY-2 compounds have also been investigated. All materials has been characterized by powder X-ray diffraction, thermal analyses (TG–SDTA–MS), FTIR spectroscopy, C–H–N elemental analysis, scanning electron microscopy (SEM-EDX), and powder X-ray thermodiffraction.

Eu3+ luminescence properties of Eu- and Mg-codoped AlGaN

We investigated the effect of Mg codoping on luminescence properties of AlGaN:Eu to improve emission through synergy effect between an increase in bandgap by AlGaN and the Mg codoping technique. The luminescence properties of AlGaN:(Eu, Mg) are strongly influenced by the Mg concentration and Al composition. Mg codoping in AlGaN was observed to contribute to increasing photoluminescence (PL) integrated intensity and to improve thermal quenching from 7.3% to 60% while the dominant optical site remained site B (622.3-nm peak) with low excitation cross section. The total concentration of optically activated Eu at 25K was a constant at for either optical site, indicating that Mg codoping did not affect the formation of optical sites. The PL decay times at room temperature (RT) increased with Mg concentration because of suppression of the back-transfer process. For optimized Mg concentration, an increase in the Al composition contributed to the total activated Eu concentration and changed the dominant optical site from A (620.3-nm peak) to B. The activation energy Ea, which is the difference in energy between the 5D0 energy level and the trap level in the host material, was estimated from temperature dependence of PL decay time. The Ea for site A was larger than that for site B, suggesting that the back-transfer rate for site A was less than that for site B.

Electrospinning preparation, thermal, and luminescence properties of Eu2(BTP)3(Phen)2 complex doped in PMMA

Different concentrations of bis-β-diketonate complex Eu2(BTP)3(Phen)2 (BTP = 1,3-bis(4,4,4-trifluoro-1,3-dioxobutyl)-phenyl and Phen = 1,10-phenanthroline) were doped into the poly(methylmethacrylate) (PMMA), forming a series of red Eu/PMMA luminescent nanofibers, via electrospinning technology. Various characterization techniques were employed to reveal the effect of Eu2(BTP)3(Phen)2 on the morphology, thermal stability, and luminescence of composite nanofibers. FT-IR spectra show the Eu2(BTP)3(Phen)2 complex was successfully doped into PMMA. The luminescent spectra of the composite nanofibers show strong characteristic emission of Eu3+ ions. Simultaneously, in comparison with the precursor complex Eu2(BTP)3(Phen)2, the Eu/PMMA nanofibers has a great improvement in thermal stability. Furthermore, the Judd-Ofelt theory and simulative constructions of the complex are employed to explain the effect of the dispersion of Eu2(BTP)3(Phen)2 and the interactions between the Eu2(BTP)3(Phen)2 complex and neighboring chain segments of PMMA.

Synthesis and luminescent properties of Eu3+-doped ZnO phosphors

Eu3+-doped ZnO phosphors were prepared with different concentrations of Eu3+ ions by using a solid-state reaction method. The synthesized samples were systematically characterized by using X-ray diffraction (XRD), scanning electron microscopy, and photoluminescence spectroscopy. The XRD patterns indicate that the intensity of the ZnO (101) peak gradually increases with increasing concentration of Eu3+ ions, with an additional Eu2O3 (222) diffraction peak appearing in samples with Eu3+ concentrations above 2 wt%. All of the phosphor samples, irrespective of the concentration of Eu3+ ion, show a dominant red emission centered at 612 nm, which originates from the 5D0 → 7F2 electric dipole transition of the Eu3+ ion. This suggests that the Eu3+ ions are mainly situated in the asymmetry centers of the host lattice.