Transition Of Eu Research Articles

Preparation and fluorescence properties of Zn2SnO4:Eu3+ orange emitting afterglow phosphor

In this study, an orange emitting afterglow phosphor of Zn2SnO4:Eu3+ was fabricated using the co-precipitation & hydrothermal method, and then annealed in Ar atmosphere at 1000 °C. X-ray diffraction, Raman spectra, EDX, fluorescence spectrometer, SEM and TEM were performed to characterize the target products. As revealed from the XRD analysis results, the fabricated product was the cubic inverse spinel structure Zn2SnO4 (JCPDS 24–1470) exhibiting high crystallinity. As confirmed by Raman and EDX spectra, the target product was Zn2SnO4:Eu3+. As Zn2SnO4:Eu3+ was excited at 347 nm, its fluorescence spectra showed the magnetic dipole emission at 589 nm and the electric dipole transition at 610 nm, complying with the transitions of Eu3+ ions from 5D0→7F1 and 5D0→7F2. Meantime, Zn2SnO4:Eu3+ phosphors displayed an orange afterglow, and its attenuating characteristics met the exponential equation. Moreover, the optimal doping amount of Eu3+ ions was 15 mol%, and the concentration quenching took place by the cross relaxation. The color coordinate of the product (x = 0.15) was determined as (0.522, 0.4635), and the color purity reached 98.3%.

Photoluminescence of Zn1 – х – yCuxEuyS/EuL3 Quantum Dots in a Polyacrylate Matrix

Zinc sulfide is one of the most popular luminescent semiconductors of the А(II)B(VI) group. Doping of ZnS quantum dots (QDs) with Ln3+ ions makes it possible to form in a semiconductor matrix nanosized structures containing isolated narrowband luminescence centers. Incorporation of QDs into ac-rylate matrices additionally stabilized particles and allows formation of their morphology. The Zn1 ‒ x ‒ yCuxEuyS/EuL3 nanosized structures, where L is a trifluoroacetate anion, are synthesized in situ in methylmethacrylate (MMA) by the method of appearing reagents. Doping of ZnS was performed by introduction of soluble zinc sulfide precursors simultaneously with copper and europium trifluoroacetates into the acrylate reaction mixture. The optically transparent polymer composites PММА/Zn1 – x – yCuxEuyS/EuL3 were obtained by radical casting polymerization of MMA. The excitation of luminescence in the composites is related to electronic interband transitions in ZnS, to the system of levels formed by dopant ions in the ZnS band gap, and to the intrinsic energy absorption by Eu3+ ions. The broadband luminescence of the composites is caused by intracrystalline defects formed in ZnS upon doping. The narrowband luminescence results from the 5D0 → 7Fj electronic transitions of Eu3+ ions bound to QDs and existing in the polymer matrix independently of them. The energy transfer from the donor levels of the semiconductor matrix to the levels of Eu3+ with subsequent luminescence is confirmed by the overlap of the absorption bands of doped ZnS and the luminescence excitation bands of the composites, as well as by an increase in the intensity of the narrowband luminescence of Eu3+ simultaneously with a decrease in the intensity of the broadband recombination luminescence of doped ZnS. The decrease in the intensity of the recombination luminescence of ZnS with increasing concentration of Eu3+ to >1.0 × 10–3 mol/L is also related to the formation of a layer of europium complex compounds on the surface of particles, which hinders the propagation of exciting radiation to the particle core.

Magnetism and Afterglow United: Synthesis of Novel Double Core-Shell Eu2+ -Doped Bifunctional Nanoparticles.

Afterglow–magnetic nanoparticles (NPs) offer enormous potential for bioimaging applications, as they can be manipulated by a magnetic field, as well as emitting light after irradiation with an excitation source, thus distinguishing themselves from fluorescent living cells. In this work, a novel double core–shell strategy is presented, uniting co‐precipitation with combustion synthesis routes to combine an Fe3O4 magnetic core (≈15 nm) with an afterglow SrAl2O4:Eu2+,Dy3+ outer coat (≈10 nm), and applying a SiO2 protective middle layer (≈16 nm) to reduce the luminescence quenching caused by the Fe core ions. The resulting Fe3O4@SiO2@SrAl2O4:Eu2+,Dy3+ NPs emit green light attributed to the 4f65d1→4f7(8S7/2) transition of Eu2+ under UV radiation and for a few seconds afterwards. This bifunctional nanocomposite can potentially be applied for the detection and separation of cells or diagnostically relevant molecules.

Enhanced Eu3+ emission in Ca2LaTaO6:Eu3+ phosphors by codoping Bi3+

The Bi3+/Eu3+ singly and codoped double perovskite Ca2LaTaO6 phosphors were made via solid-phase sintering with the addition of H3BO3. X-ray powder diffraction patterns, morphology, particle size, and photoluminescence properties of them were researched. All of Bi3+/Eu3+ singly and codoped Ca2LaTaO6 phosphors have the same phase with pure Ca2LaTaO6. And all of phosphors have similar morphology and particle size. Exciting at 275 nm, Ca2La1−xEuxTaO6 (x = 0.1, 0.2, 0.3, 0.4, and 0.5) phosphors exhibit bands resulting from 5D0 → 7FJ (J = 0, 1, 2, 3, and 4) transitions of Eu3+. It is found that the critical doping concentration of Eu3+ in Ca2LaTaO6 is about 0.4. Exciting at 272 nm, Ca2La1−yBiyTaO6 (y = 0.05, 0.1, and 0.15) phosphors exhibit emission bands corresponding to the 3P1 → 1S0 transition of Bi3+. There is the occurrence of energy transfer in Bi3+/Eu3+ codoped Ca2LaTaO6 phosphors, which benefits to the enhancement of Eu3+ emission intensity.

Spectral response characteristics of Eu3+ doped YAG-Al2O3 composite nanofibers reinforced aluminum matrix composites

Stress and strain in the deformation zone have very important impact on the performance of fiber reinforced aluminum matrix composites, but it is still difficult to detect and analyze the stress-strain intuitively. In this paper, the rare-earth ion Eu3+ as a luminous center was doped into the YAG-Al2O3 composite short-nanofibers by an electrospinning method, and afterwards these luminescent fibers were compounded with aluminum alloy powders and sintered to form fiber-reinforced composites. The changes of emission spectrum of the fiber-reinforced aluminum matrix composites under different tensile stresses were studied by the spectral response. Results showed that the Eu3+ doped YAG-Al2O3 composite short-nanofibers prepared by electrospinning had a stress-luminescence property and can effectively improve the mechanical property of the aluminum matrix composites (Eu3+ doped YAG-Al2O3 composite short-nanofibers are abbreviated as (YAG:Eu3+-Al2O3)csf in the following description). The excitation spectra of (YAG:Eu3+-Al2O3)csf showed a charge transfer belt in the range of 350–390 nm and its emission spectra exhibited the 5D0-7Fj (j=0, 1, 2, 3, 4) transitions of Eu3+. The ultimate tensile strength (UST) of (YAG:Eu3+-Al2O3)csf reinforced Al matrix composites reached 300.1 MPa with the content of (YAG:Eu3+-Al2O3)csf was 1 wt% ((YAG:Eu3+-Al2O3)csf reinforced Al matrix composites are abbreviated as (YAG:Eu3+-Al2O3)csf/Al composites in the following description). Under the action of applied load, the tensile stress was linearly related to the barycenter wavelength of fluorescence emission spectrum in the deformation region of (YAG:Eu3+-Al2O3)csf/Al composites.

Synthesis and photoluminescence properties of novel red-emitting KBaLu(MoO4)3:Eu3+ phosphors with high thermal stability and high color purity

In this paper, we reported on the photoluminescence properties of novel Eu3+-activated KBaLu(MoO4)3 red-emitting phosphors. Under 395 and 465 nm excitations, the as-prepared samples gave bright sharp red emissions around 592, 615, 655, and 701 nm, corresponding to 5D0→7FJ (J = 1, 2, 3, and 4) transitions of Eu3+ ions. The 615 nm red emission due to the 5D0→7F2 transition was dominant in the emission spectra, indicating the Eu3+ ions occupied non-inversion centrosymmetric sites in KBaLu(MoO4)3 host lattice. Eu3+ doping concentration dependent luminescence properties were studied, and the KBaLu(MoO4)3:0.8Eu3+ sample exhibited the strongest emission intensity. The CIE color coordinates and color purity of the optimal KBaLu(MoO4)3:0.8Eu3+ sample were determined to be (0.6655, 0.3311) and 96.7%, respectively. Besides, temperature-dependent emission spectra demonstrated that the KBaLu(MoO4)3:0.8Eu3+ phosphors also exhibited excellent thermal stability (I423k/I303k = 88%) with activation energy △E of 0.204 eV. These obtained results indicated that the newly discovered KBaLu(MoO4)3:Eu3+ red phosphors were promising color converters for application in white light-emitting diodes and display devices.

Cost-effective ZnO–Eu3+ films with efficient energy transfer between host and dopant

The present work focuses on the deposition of Europium (Eu3+) incorporated zinc oxide (ZnO) film by a cost effective chemical solution deposition method. ZnO film with varying concentration of Eu3+ ions (2, 3 and 4 atomic percent) were deposited and characterized using different techniques like X-ray diffractogram (XRD), scanning electron microscopy. XRD studies revealed that highly c-axis oriented ZnO films without showing any segregation of europium oxide were obtained at 650 °C. The optical properties were determined using UV–visible spectrophotometry and photoluminescence measurements. UB-visible spectroscopy revealed that Eu3+ doping shifted optical band gap with increase in transparency of the films. The Eu3+ doped film showed intense emission at 614 nm which was attributed to the defect emission from ZnO that gets trapped by Eu3+ ions ultimately leading to 7F2 to 5D0 transition in Eu3+.

Synthesis and optical studies of nanocrystalline Eu2+-doped and RE3+(Nd3+, Dy3+)-codoped Ba4Al14O25 materials for UV-LEDs

Green emitting Ba4Al14O25:Eu2+ and Ba4Al14O25:Eu2+,RE3+ (RE3+ = Nd3+, Dy3+) phosphors for ultraviolet light emitting diodes (UV-LEDs) were prepared via combustion technique at 600 °C. The as-prepared samples were reheated at 1150 (2 h) and 1350 °C (6 h) in a tube furnace under reducing condition (95 % dinitrogen and 5 % dihydrogen). The photoluminescence emission (PL) spectra were recorded to examine the effect of temperature and presence of codopants on the luminescence properties of materials. On excitation at 362 nm, PL spectra of these phosphors exhibited intense band at 480−520 nm due to spin-allowed 4f65d1→4f7 transition in Eu2+. The luminescence intensity and persistence behaviour of materials was improved in presence of Nd3+ and Dy3+ ions as codopants. The diffraction analysis confirmed the synthesis of lattice having orthorhombic structure with Pmma symmetry. The crystalline nature of samples was found to be increased at higher temperature. Transmission electron microscope (TEM) images exhibited that the prepared materials have nearly spherical shape in nano-range. The structure and chemical bonding of materials were supported by Fourier transform infrared (FTIR) spectra.

Implanting bismuth in color-tunable emitting microspheres of (Y, Tb, Eu)BO3 to generate excitation-dependent and greatly enhanced luminescence for anti-counterfeiting applications

ABSTRACT To prevent counterfeiting, a lot of advanced security technologies have been developed, including luminescent printing. Therefore, the pigments with advanced security features are urgently pursued for luminescence printing-based anti-counterfeiting technology. Here, micron-sized spheres of hexagonal-structured and color-tunable emitting (Y, Tb, Eu, Bi)BO3 have been rapidly synthesized by microwave processing, followed by a proper annealing. Incorporation of Bi3+ greatly enhances the emission intensity of Eu3+ and of Tb3+. Under the excitation at 260 nm, the spheres exhibit UV emission at 330 nm (3P1→1S0 transition of Bi3+), green emission at 546 nm (5D4→7F5 transition of Tb3+) and orange-red emission at 592 nm (5D0→7F1 transition of Eu3+), mainly due to the three energy transfer processes of Bi3+→Tb3+, Bi3+→Eu3+, and Tb3+→Eu3+. However, under the excitation at 230 nm, the Tb3+→Eu3+ energy transfer contributes to the orange-red emission of Eu3+ and the green emission of Tb3+, in the absence of Bi3+ emission. The maximum energy transfer efficiency of Bi3+→ “Eu3+ and Tb3+” and Tb3+→ Eu3+ is 63% and 50% for (Y0.883Tb0.02Eu0.09Bi0.007)BO3. The (Y0.963Tb0.02Eu0.01Bi0.007)BO3 spheres exhibit a distinct excitation-dependent luminescence behavior. Facile switching the excitation wavelength from 260 nm to 230 nm yields emission color changing from orange to green yellow, which possesses the advanced security feature.

Europium Doped Magnesium Zinc Sulfophosphate Glass as Potential Red Laser Host

Demand for rare earth ions (REIs) doped inorganic glasses have been ever-increasing for diverse photonic applications. Synthesis of these glasses needs the appropriate choice of suitable host matrices, modifiers, and REIs as dopants to improve their spectroscopic traits. In this realization, a new series of magnesium-zinc-sulfophosphate glasses were prepared with varied europium ions (Eu3+) doping contents (0 to 2.0 mol%). Such melt-quench synthesized glasses were characterized at room temperature by diverse analytical techniques to determine their physical and optical properties. XRD pattern of as-quenched samples confirmed their amorphous nature. Densities of the glass system were observed to increase from 2.540 to 2.788 g.cm−3 with the increase in Eu3+ doping contents from 0 to 2.0 mol% which were attributed to the generation of more bridging oxygen atoms and enhanced network compactness. Photoluminescence (PL) emission spectra of glasses exhibited four characteristic peaks positioned at 593, 613, 654 and 701 nm assigned to corresponding 5D0→7F0, 5D0→7F2, 5D0→7F3, and 5D0→7F4 transitions in Eu3+, in which the intensity of the peak at 613 nm (red) was highest. Emission intensities of all peaks were enhanced with the rise in Eu3+ content up to 1.5 mol% and quenched thereafter. It was affirmed that the physical and optical traits of these glass compositions can be improved by adjusting the Eu3+ doping contents. The proposed glass compositions may be potential for the development of varied photonic devices especially for eye safe solid-state red laser and fibre sensors.

Synthesis of novel Eu2+ activated K3Ca2(SO4)3F down-conversion phosphor for near UV excited white light emitting diode

In the present paper, we have successfully synthesized Eu2+ activated K3Ca2(SO4)3F phosphor by two-step solid-state reaction method at high temperature (800 °C). Pure crystalline formation, morphological behavior, and their vibration bonds of synthesized Eu2+ activated K3Ca2(SO4)3F phosphor were verified by the X-ray diffraction (XRD), Scanning Electron Microscopy (SEM) and Fourier transform Infrared Spectrum (FT-IR). The photoluminescence (PL) spectrum and CIE coordinate with color purity also characterized. In PL emission spectra clearly represented that broad excitation band from 250 nm to 400 nm ranged. The center of this PL excitation spectra observe at 326 nm, but some parts of these spectra lies to 350 nm–400 nm. This excitation wavelength is very useful for the generation of white light because it may be used as near UV light. PL emission represents broad emission spectra from 400 nm to 550 nm centred at 440 nm. Most part of these PL emission spectra lies in the blue region of the spectrum. PL spectra arise from the transitions between the 5d and 4f orbital’s transition of Eu2+ ions. EVI parameters such as Stokes Shift (ΔEs), the Huang-Rhys factor (S),effective phonon energy (ħω) and the Zero-phonon line (ZPL) are calculated. In our present work, we are calculated that the value of Huang–Rhys factor constant (S) is 3.74 that means coupling is intermediately strong. CIE chromaticity coordinate of K3Ca2(SO4)3F:xmol%Eu2+[x = 0.5, 2.0, 3.0, 5.0, 7.0, 10mol%] phosphor were also calculated by using OSRAM SYLVANIA color calculator 1931. By using these CIE chromaticity coordinate was calculated the value of color purity for each concentration of Eu2+ ions. After seeing all results of synthesized phosphor material we are concluded that it may be a better option used as commercial phosphor for obtaining white light. So it may be a promising candidate for NUV WLEDs.

Europium-doped boro-telluro-dolomite glasses for red laser applications: Basic insight into spectroscopic traits

Naturally abundant minerals and lanthanide-doped synthetic boro-tellurite networks have become prospective efficient laser hosts because of the synergy between them. Driven by this idea, Eu3+-doped boro-telluro-dolomite (BTD) glasses were prepared via the melt-quenching method. The spectroscopic traits of as-quenched samples were analyzed though experimental and theoretical studies. The result from the derivation of absorption spectral fitting (DASF) model demonstrated the direct allowed transition in the glasses. Moreover, the photoluminescence spectra of the sample containing 1.0 mol% of Eu3+ (BTD1.0Eu glass) revealed a prominent red peak at 611 nm (assigned to 5D0 → 7F2 transition in Eu3+ ion) with a large stimulated emission cross section (7.15×10−22cm2) and a high luminescence branching ratio (61.5%). Furthermore, the attained CIE color coordinates (0.637, 0.363), which lie near the standard red hue (0.67, 0.33), together with high quantum efficiency (92.7%) affirmed the effectiveness of BTD1.0Eu glass as a potential red laser host.

Phase transition and fluorescence regulation of BaAl2Si2O8:Eu using Ba source

In this investigation, BaAl2Si2O8 (BAS):Eu2+ (BaF2-derived BAS:Eu and BaCO3-derived BAS:Eu) series of blue phosphor samples were synthesized through high-temperature solid-phase method, and their structure and luminescence properties were examined. In the case of BaF2-derived BAS:Eu, hexagonal feldspar (BaAl2Si2O8) was obtained, which exhibited a UV region (λem = 372 nm) fluorescence at 300 nm excitation. In the case of BaCO3-derived BAS:Eu, a monoclinic feldspar (BaAl2Si2O8) was obtained, which exhibited a blue region (λem = 428 nm) fluorescence at 300 nm excitation. The luminescence mechanism was the f-d transition of Eu2+, and the Eu2+ underwent different degrees of 5 d energy level splitting in different crystal field environments. This accounted for the UV region and blue region fluorescence. Considering that the phase transition between the hexagonal and monocline phases is a slow process, fluorescence emissions in UV and blue regions were generated during the two-phase transition period. As a result, phosphor exhibited a controllable spectrum from UV region (λem = 372 nm) to blue region (λem = 428 nm). Furthermore, based on the crystal field splitting formula, the blue-shift phenomenon of the spectrum was shown to occur in the monoclinic phase. Finally, the crystal distortion index of the environment of Eu2+ was calculated.

Luminescence properties of novel red-emitting phosphors Ba3B6Si2O16: Eu3+ for near-UV excited LED

A novel Eu3+ doped Ba3B6Si2O16 red-emitting phosphor was synthesized by a high temperature solid state reaction and its luminescence properties were investigated. All the phosphors are pure phase of triclinic Ba3B6Si2O16 in structure. Under 393 nm excitation, Ba3B6Si2O16: Eu3+ phosphor exhibits intense red emissions due to the characteristic f–f transitions of Eu3+ with the strongest emission peaks at 613 nm. The optimum doping concentration of Eu3+ is 0.09 and the corresponding critical distance is estimated to be 23.9 Å. The emission intensity decreases with increase of Eu3+ ion concentration(x>0.09) due to dipole-dipole interactions among Eu3+. Ba3B6Si2O16: Eu3+ phosphor exhibits high color purity (92 %), good thermal stability (the activation energy of 0.2121 eV) and high quantum efficiency (36.5 %) with CIE chromaticity coordinates of (0.6460, 0.3534). These results indicate that Ba3B6Si2O16: Eu3+ phosphor can be anticipated as a red emitting phosphor for near-UV pumped white LEDs.

Synthesis of mesoporous core-shell structured GdPO4:Eu@SiO2@mSiO2 nanorods for drug delivery and cell imaging applications

Mesoporous GdPO4:Eu@SiO2@mSiO2 core-shell nanorods (NRs) were prepared by a facile two-step method. First, the monodispersed GdPO4:Eu NRs were obtained on a large scale via a facile precipitation method, then mesoporous silica was wrapped onto their surface through hydrolysis of tetraethylorthosilicate (TEOS). The XRD result indicates that the as-prepared GdPO4:Eu NRs core has hexagonal phase. The FTIR and the N2 adsorption/desorption isotherm analysis confirm the successful coating of mesoporous silica. The TEM images show that the obtained GdPO4:Eu@SiO2@mSiO2 NRs exhibit uniform monodisperse core-shell structure with a nanorod core (length of 200 nm; width of 20 nm), and mesoporous silica shell of 15 nm. Under excitation of 274 nm, GdPO4:Eu@SiO2@mSiO2 NRs show strong red luminescence from 5D0 →7FJ (J = 1, 2, 3 and 4) transitions of Eu3+. Furthermore, the GdPO4:Eu@SiO2@mSiO2 NRs exhibit obvious T1 enhancement effect due to paramagnetism of Gd3+. The drug loading capacity and pH-sensitive releasing behavior of the as-prepared GdPO4:Eu@SiO2@mSiO2 NRs were studied by using doxorubicin (DOX) as model drug. The excellent biocompatibility of GdPO4:Eu@SiO2@mSiO2 NRs was demonstrated by MTT assay. Taken together, the mesoporous GdPO4:Eu@SiO2@mSiO2 NRs may be potentially applied in fields of drug delivery and dual-modal imaging.

Characterization, packaging, and optical model of single-primary color phosphor thin films and LEDs

Blue, green, and red phosphor thin films (PTFs) used for NUV LED were prepared by hot pressing method. The excitation spectrums of PTFs have broadband absorption characteristics owing to the 4f7 → 4f65d transition of Eu2+; the emission peaks are 445 nm, 520 nm, and 627 nm, respectively. The phosphor conversion efficiency (PCE) gradually increases and finally remains unchanged with phosphor mass fractions because of absorption saturation effect. Different color LEDs are packaged by NUV chips and PTFs; spectral decomposition and data fitting methods are used to achieve the fitting of the relationship between the phosphor mass fraction and the emission light intensity of the NUV chip and phosphor. The double Gaussian model is used to express the spectral power distribution (SPD) of a single-primary color LED and compare it with the measured results. White LEDs (WLEDs) were prepared by two methods, the first is the combination of multi-LEDs, the second is NUV chip pumps three-color-mixed phosphor directly. Experimental results showed that the WLEDs prepared by first method with the light color parameters of CCT = 5342 K, LER = 274 lm/W, show small parameter difference of ΔCCT = 24 K, ΔLER = 15 lm/W, NCC = 98.94% compared with the calculated results. The WLEDs prepared by second method with the light color parameters of CCT = 5292 K, LER = 263 lm/W shows a 4.0% decrease in LER.

Spectroscopic analysis of alkaline-earth metal (Mg, Ca, Sr and Ba) co-doped Gd2O3:Eu phosphors synthesized via co-precipitation route.

This paper reports the effect of alkaline earth metals (AEM=Mg2+, Ca2+, Sr2+, Ba2+) co-doping on the structural, morphological and luminescent properties of Gd2O3:Eu phosphors. The concentration of the Eu3+ ions was fixed 4mol% to avoid the chances of the concentration quenching. AEM co-doped Gd2O3:Eu XRD profile confirmed the synthesis of cubic-phase of all the co-doped samples. FESEM micrographs exhibited the rod like morphology of the synthesized phosphors. All the samples were irradiated under UV excitation and exhibited intense, sharp and narrow emission spectra corresponding to the characteristic transitions (5D0→7F1,2,3,4) transitions of Eu3+ ions. The photometric parameters such as CIE coordinates, CCT and color purity are calculated. In order to probe the further luminescent properties and influence of the of alkaline earth metals on the local environment of the Eu ions in the host lattice, spectral parameters are calculated from Judd Ofelt theory from emission spectra. The obtained results suggest that AEM can be effectively utilized to enhance the luminescence intensity even after concentration quenching. The as-synthesized phosphors can be used in various solid state lighting devices and bio-sensors.

Фотолюминесценция квантовых точек Zn-=SUB=-1-x-y-=/SUB=-Cu-=SUB=-x-=/SUB=-Eu-=SUB=-y-=/SUB=-S/EuL-=SUB=-3-=/SUB=- в полиакрилатной матрице

Zinc sulfide is one of the most popular luminescent semiconductors of group A(II)B(VI). Doping ZnS quantum dots with Ln3+ ions makes it possible to form nanoscale structures in a semiconductor matrix containing isolated centers of narrow-band luminescence. The introduction of quantum dots into the acrylate matrix further stabilizes the particles and allows them to form their morphology. Nanoscale structures of Zn1-x-yCuxEuyS/EuL3, where L − trifluoroacetate are anions, were synthesized by the method of emerging reagents in situ in the medium of methyl methacrylate (MMA). ZnS doping was performed by simultaneous introduction of soluble precursors of zinc sulfide, as well as copper and europium trifluoroacetates into the acrylate reaction mixture. Polymer optically transparent compositions of PMMA/Zn1-x-yCuxEuyS/EuL3 were obtained by radical polymerization of MMA in the block. The excitation of luminescence of compositions is associated with Interzone electron transitions in ZnS, with a system of levels that form alloying ions in the forbidden zone of ZnS, as well as with their own energy absorption by Eu3+ ions. Broadband luminescence of compositions is caused by intracrystalline defects formed in ZnS during doping. Narrow-band luminescence occurs as a result OF 5D0→7Fj electronic transitions in Eu3+ ions associated with quantum dots, as well as being in the polymer matrix independently of them. The transfer of energy from the donor levels of the semiconductor matrix to the levels of Eu3+ ions, followed by its release in the form of luminescence, was confirmed by the imposition of absorption bands doped with ZnS and excitation bands of luminescence compositions, as well as an increase in the intensity of narrow-band luminescence of Eu3+ ions while reducing the intensity of a wide band of recombination luminescence of doped ZnS. A decrease in the intensity of the ZnS recombination luminescence band with an increase in the concentration of Eu3+ >1.0∙10-3 mol/L ions is also associated with the formation of a layer of complex europium compounds on the particle surface that prevent the passage of exciting radiation to the particle core.

Influence of Al3+ co-doping on the spectral properties of europium doped Ca9Y(PO4)7.

A series of luminescent materials based on a calcium yttrium phosphate matrix doped with europium and different concentrations of aluminum ions (0, 5, 10% of mole) was synthesized using the Pechini method. A two-step strategy of synthesis was applied. Phase composition analysis and spectroscopic measurements were performed to characterize the obtained phosphors. The XRD patterns show that in all cases the obtained materials consist of a pure phase of Ca9Y(PO4)7. Emission spectra of the materials obtained after the first step of the synthesis consist of narrow bands attributed to 5D0–7FJ transitions in Eu3+ ions. Independently of the aluminum concentration, europium ions are incorporated into at least two different cationic sites. Considering the asymmetric ratio (R), the sites are characterized by the presence/absence of inversion symmetry. The emission intensity of Eu3+ introduced into the more symmetric site decreases with increasing aluminum concentration. The emission spectra of the materials after the reduction process are characterized by intensive broad bands located at 420 and 488 nm attributed to the d–f transitions in Eu2+; however, the line shape of the spectra depends on the aluminum concentration. Moreover, incorporation of aluminum ions causes the stabilization of the Eu3+ ions under a reductive atmosphere.

Novel red-emitting Lu3Te2Li3O12: Eu3+ phosphor with high color purity for n-UV WLEDs

In this work, a series of red emitting Lu3Te2Li3O12: Eu3+ phosphors were synthesized for the first time by high temperature solid state reaction. The structure was characterized by X-ray diffraction. The excitation spectra, emission spectra and CIE chromaticity coordinate were studied. The phosphors show strong red emission at 611 nm due to the 5D0-7F2 transition of Eu3+ ions. The optimal doping concentration of Eu3+ in LTL host is x = 0.5 due to the concentration quenching mechanism of dipole-dipole interaction. The CIE chromaticity coordinates of the LTL: 0.5Eu3++ phosphor is (0.644,0.355), and the purity of the color is up to 93.61%. The phosphor can be considered as a potential red-emitting candidate for near UV WLEDs.