Structural and spectroscopic properties of Eu3+-doped zinc fluorophosphate glasses (original) (raw)

Characterization of Eu3+-doped fluorophosphate glasses for red emission

Journal of Non-Crystalline Solids, 2007

Fluorescence spectra and decay curves of the 5 D 0 level for different concentrations of Eu 3+ (4f 6) ions in K-Ba-Al fluorophosphate glasses have been measured at room temperature and are analyzed. The Judd-Ofelt intensity parameters X 2 and X 4 have been determined from the intensity ratios of emission peaks corresponding to 5 D 0 ! 7 F J (J = 2 and 4) to 5 D 0 ! 7 F 1 transitions for 1.0 mol% glass. The intensity parameters thus obtained are in turn used to calculate the radiative properties of the fluorescent levels of Eu 3+ ions. Second and fourth rank crystal-field parameters have been evaluated by assuming a C 2V site symmetry for the local environment of Eu 3+ ions to estimate the crystal-field strength experienced by Eu 3+ ions in the present host. The decay profiles of the 5 D 0 ! 7 F 2 transition of Eu 3+ ions in the present glasses are found to be single exponential for all the studied Eu 3+ ion concentrations. A marginal increase in lifetime of the 5 D 0 level has been noticed with Eu 3+ ion concentration up to 2.0 mol% and then the lifetime marginally decreases for higher Eu 3+ ion concentrations.

Influence of the Structure on the Properties of Na x Eu y (MoO 4 ) z Red Phosphors

Chemistry of Materials, 2014

Scheelite related compounds (A′,A″) n [(B′,B″)O 4 ] m with B′, B″ = W and/or Mo are promising new materials for red phosphors in pc-WLEDs (phosphor-converted white-light-emittingdiode) and solid-state lasers. Cation substitution in CaMoO 4 of Ca 2+ by the combination of Na + and Eu 3+ , with the creation of A cation vacancies, has been investigated as a factor for controlling the scheelite-type structure and the luminescent properties. Na 5 Eu(MoO 4 ) 4 and Na x Eu 3+

Synthesis and Photoluminescence Properties of the High-Brightness EU3+

2017

Eu3+ doped red phosphors Li0.5Al0.5Mg2 (MoO4)3 were prepared by the combustion method, and their luminescent properties were studied. Under the excitation of nearUV 395 nm, the phosphors show intense red emission with the peaks located at 615 and 595 nm. The influence of Eu3+ concentration on the luminescent properties of Eu3+ doped Li0.5Al0.5Mg2(MoO4)3 was investigated and the 3% (mole fraction) was the appropriate molar concentration. By sintering Li0.5Al0.5Mg2(MoO4)3:xEu3+ phosphor at 750°C, PL intensity has a maximum value at 615 nm with Commision Internationale de I’Eclairage 1931 (CIE 1931) chromaticity coordinates (0.6616, 0.3336) . The phosphor could be suitable for the application of white light-emitting diodes.

Structure and spectroscopic properties of (Y, Eu)(PO3)3 polyphosphate red phosphors

Solid State Sciences, 2016

A series of orange-red emitting phosphor Y(PO 3) 3 : xEu 3þ (x ¼ 0.1e1.0) was prepared by a solid-state reaction route. The phosphors were characterized by X-ray diffraction (XRD) and photoluminescence (PL) as well as decay lifetimes. Studies revealed the phase transfer from monoclinic to orthorhombic when Y 3þ is totally replaced by Eu 3þ , and expansion of the unit cell occurs with increasing Eu 3þ doped content. The PL spectra show that the phosphors Y(PO 3) 3 : xEu 3þ can be effectively excited by near ultraviolet (n-UV) light, and exhibit strong red-orange emission with no concentration quenching. The profile of PL spectra changes significantly at high Eu 3þ content (x ! 0.80), which is due to the variation of preference for substitution of Eu 3þ. The luminescence due to the 5 D 0 / 7 F J (J ¼ 1, 2) transitions at 77 K exhibits its own spectral features for different crystallographic site. It is found that Eu 3þ ions occupy the centers of octahedral polyhedron and form C i /C 1 point group in Y(PO 3) 3 .

Investigations on the luminescence properties of Na0.34Ca0.66Al1.66Si2.34O8:Eu2+/Eu3+/Sm3+ phosphors

Solid State Sciences, 2015

Rare Earth doped-phosphate glasses have received a great deal of attention on research because of their applications in biomaterial engineering, however, little to no attention has been given to potential luminescent properties from "heating" these materials when exposed to ionizing radiation. This paper aims to presents results on investigations of Thermoluminescent (TL) and Optically Stimulated Luminescence (OSL) properties of the Er 3+-doped phosphate glasses produced at the Physics Department of Federal University of Juiz de Fora on a characterization for beta radiation dosimetry. It was used a RISØ TL/OSL reader and its coupled 90 Sr/ 90 Y beta source. The experimental findings indicate that the mate bands on 350-380nm from Er 3+. Further investigations are being carried out on its applications to other types and qualities of radiation.

Luminescence and luminescence quenching of highly efficient Y2Mo4O15:Eu3+ phosphors and ceramics

Scientific Reports, 2016

A good LED phosphor must possess strong enough absorption, high quantum yields, colour purity, and quenching temperatures. Our synthesized Y 2 Mo 4 O 15 :Eu 3+ phosphors possess all of these properties. Excitation of these materials with near-UV or blue radiation yields bright red emission and the colour coordinates are relatively stable upon temperature increase. Furthermore, samples doped with 50% Eu 3+ showed quantum yields up to 85%, what is suitable for commercial application. Temperature dependent emission spectra revealed that heavily Eu 3+ doped phosphors possess stable emission up to 400 K and lose half of the efficiency only at 515 K. In addition, ceramic disks of Y 2 Mo 4 O 15 :75%Eu 3+ phosphor with thickness of 0.71 and 0.98 mm were prepared and it turned out that they efficiently convert radiation of 375 and 400 nm LEDs to the red light, whereas combination with 455 nm LED yields purple colour. Solid state light sources based on the blue emitting InGaN semiconductor chips became a revolution in lighting industry after the discovery of efficient blue emitting diode by S. Nakamura in 1991 1. However, the blend of the blue light emitted by diode and yellow emitted by a Y 3 Al 5 O 12 :Ce 3+ (YAG:Ce) phosphor usually yields a cold white light due to deficiency of the red component in the spectrum. To overcome this issue some red phosphors are added to the light source. Frequently used nitride based red phosphors are very expensive and require complicated synthesis techniques. Another way to produce solid state white light sources is to employ near UV emitting LED chip and coat it with red, green and blue phosphor. The advantage of such approach is much broader phosphor selection than for blue LED excitation. Inorganic materials doped with rare earth ions are mostly used as activators in the mentioned phosphors. Since there are some efficient blue (BaMgAl 10 O 17 :Eu 2+) and green (SrSi 2 O 2 N 2 :Eu 2+ , Ba 2 SiO 4 :Eu 2+) 2,3 phosphors, the main problems arise with finding a suitable and relatively inexpensive red-emitting phosphor. Moreover, the requirements for LED phosphors are also high, for instance, strong absorption of LED radiation, high thermal quenching temperature, high quantum yield, excellent chemical and thermal stability and absence of emission saturation at high fluxes 4. Unfortunately, it is very hard to find materials that meet all the aforementioned criteria and, therefore, the reports of efficient Eu 3+ doped phosphors with high thermal stability is scarce. Trivalent europium doped materials are usually considered as good red-emitting phosphor candidates for LEDs. On the other hand, Eu 3+ ions typically possess rather low absorption strength due to the spin and parity forbidden nature of their intraconfigurational [Xe]4f 6 → [Xe]4f 6 transitions 5. However, in molybdates, tungstates, niobates and vanadates these transitions, especially at shorter wavelengths (< 400 nm), become rather strong due to admixing with low lying charge transfer (CT) band 6-8. The position of the CT band depends on the host material as do the emission spectra of Eu 3+ ions. Thus by selecting the appropriate host material one should be able to obtain a desired absorption strength and emission profile.

Effect of Eu3+ Concentration on Luminescence Studies of Y4Al2O9 Phosphor

Indian Journal of Materials Science, 2014

The present paper reports the effect of europium concentration on photoluminescence (PL) and thermoluminescence (TL) studies of Eu3+ doped Y4Al2O9 phosphor using inorganic materials like yttrium oxide (Y2O3), aluminium oxide (Al2O3), boric acid (H3BO3) as a flux, and europium oxide (Eu2O3). The sample was prepared by the modified solid state reaction method, which is the most suitable for large-scale production. The prepared phosphor sample was characterized using X-ray diffraction (XRD), field emission gun scanning electron microscopy (FEGSEM), Fourier transform infrared spectroscopy (FTIR), photoluminescence (PL), thermoluminescence (TL), and CIE techniques. The PL emission was observed in the range of 467, 535, 591, 611, 625, and 629 nm for the Y4Al2O9 phosphor doped with Eu3+ (0.1 mol% to 2.5 mol%). Excitation spectrum was found at 237 and 268 nm. Sharp peaks were found around 591, 611, and 625 nm with high intensity. From the XRD data, using Scherer’s formula, the calculated av...

Eu 2 + luminescence in the EuAl 2 O 4 concentrated phosphor

Radiation Measurements, 2007

Powder samples of EuAl 2 O 4 and (Eu, Sr)Al 2 O 4 with a quantum efficiency (QE) of the Eu 2+ emission more than 0.30 were synthesized. A modified method of QE determination is described and results of the QE measurements for EuAl 2 O 4 , (Eu 0.8 Sr 0.2 )Al 2 O 4 , (Eu 0.65 Sr 0.35 )Al 2 O 4 , and a diluted sample (Sr 0.98 Eu 0.02 )Al 2 O 4 are presented. Excitation and emission spectra as well as decay behaviour of the Eu 2+ luminescence in (Eu 1−x Sr x )Al 2 O 4 in the temperature region of 20-300 K are studied. It is concluded that the main reason for the high QE is a pronounced relaxation of the crystal lattice after excitation of the Eu 2+ ions resulting in an emission with a large Stokes shift and, therefore, in a restriction of energy migration. Eu ions occupying the crystallographic sites with the higher coordination number (Eu II ) are supposed to be the luminescence centres in (EuSr)Al 2 O 4 lattice.

Red phosphor based on Eu3+-doped Y2(MoO4)3 incorporated with Au NPs synthesized via Pechini's method

Optical Materials, 2018

Structural, morphological and spectroscopic characterization of the Eu 3+-doped Y 2 (MoO 4) 3 red phosphor incorporated with Au nanoparticles (Au NPs) synthesized via Pechini's method is reported in the present study. In order to evaluate the Au NPs and Eu 3+ ions influence on the molybdate structure, the Y 2 (MoO 4) 3 , Y 2 (MoO 4) 3 :Eu 3+ , Y 2 (MoO 4) 3 /Au and Y 2 (MoO 4) 3 :Eu 3+ /Au samples were produced and fully investigated. All samples obtained at relatively low temperature, i.e., 650°C, show molybdate as the unique phase with high crystallinity assisted by both Eu 3+ ions and Au NPs. Water molecules detected in the molybdate structure probably are distorting MoO 4 , YO 6 and EuO 6 polyhedra similarly to the Au NPs incorporated in the same lattice. These Au NPs are spherical-shaped with a diameter near to 46 nm and they are located on the molybdate particle surface. The Eu 3+-doped phosphors, with or without the presence of Au NPs, exhibit intense red luminescence characteristic of the Eu 3+ ion inserted in low-symmetry sites. However, the Au NPs increase the radiative emission rate and absolute quantum yield of the Eu 3+ 5 D 0 emitter state due to the excitation field enhancement caused by the local surface plasmon resonance absorption effect of gold nanoparticles, which was confirmed by diffuse reflectance measurements. Finally, the Eu 3+ quantum efficiency enhancement to 92% played by the gold nanoparticles and the high red color purity qualify the obtained phosphor for photonic applications.