Effect Of Eu Research Articles

Effect of Eu2+ doping on structural, optical, magnetic and photovoltaic properties of ZnS quantum dots

ZnS and Eu2+: ZnS QDs with different doping concentrations were prepared by co-precipitation method at room temperature. It was observed that all samples form in cubic structure. The Eu2+ (0.1%): ZnS, Eu2+ (0.3%): ZnS and Eu2+ (0.5%): ZnS QDs display broad photoluminescence emission peaks at 513.5 nm, 511. 7 nm and 510.6 nm, respectively, are related to the Eu2+ intra-ion transition of 4f6d1 – 4f7. The M-H measurements indicated that unlike ZnS QDs, Eu2+: ZnS QDs with different doping concentrations indicates ferromagnetic behavior at room temperature. The incident photon to electron conversion efficiency (IPCE) is improved with the Eu2+ doping, which proposes the QD solar cell efficiency is able to be boosted by Eu2+ doping by reason of broadened absorption spectra. Accordingly, the data point out that Eu2+: ZnS QDs with different doping concentrations are able to be appropriate materials for photovoltaic and spintronic applications.

Synthesis and photoluminescence of Eu3+ and O2- co-doped ZnS nanoparticles with yellow emission synthesized by a solid-state reaction

ZnS:Eu, O nanoparticles were synthesized by a solid-state reaction at 90°C for the first time. The effect of Eu3+ and O2- co-doping on the photoluminescence (PL) of the samples was researched. X-ray diffraction (XRD), transmission electron microscopy (TEM), energy-dispersive X-ray spectrum (EDS), ultraviolet-visible diffusion reflection spectra, and PL spectra were used to characterize their crystal structure, chemical compositions, diameter, and PL properties. The results showed that all nanoparticles had a cubic blende crystal structure and an average crystallite size of 3.3–4.0nm. Besides the emission from the ZnS host, typical luminescence of Eu3+ was all observed in the emission spectra of ZnS:Eu, O nanoparticles, and ZnS:Eu, O nanoparticles showed yellow emissions under 464nm excitation. The PL intensity remarkably increased with the increase of O2- concentration, and the maximum emission with correlated color temperature ~ 2419K was obtained in the ZnS:1% Eu, 5% O sample, and about 2.75 times stronger than the undoped ZnS nanoparticles. Mechanism for the enhanced luminescence was discussed. This work suggests that Eu3+ and O2- co-doped ZnS nanoparticles prepared by the low temperature solid-state reaction method can be used for Light-Emitting Diodes.

Synthesis and photoluminescence properties of Eu2+ activated CaO ceramic powders for near-ultraviolet chip based white light emitting diodes

In this paper, we synthesized series of Eu2+ activated CaO ceramic powders by conventional solid state reaction. Using NH4Cl as a reducing additives, the Eu3+ has been successfully reduced to Eu2+. An intense blue emission peaked at 460 nm from Eu2+ was observed. The luminescent intensity of the doping-optimized CaO:Eu2+ sample can be as high as 106% of commercial BAM blue phosphor under 400 nm near-ultraviolet (NUV) excitation. The effect of Eu2+ and NH4Cl contents on photoluminescence properties and crystal phase formation have been investigated, respectively. The thermal stable property which is an important performance for LED application has also been measured. The emission intensity at 120 °C can maintain 94% of that at room temperature. Our results suggest that CaO: Eu2+ ceramic powder could be used as a promising blue emitting phosphor for NUV chip based white LEDs.

Luminescent properties of single-phase Ba2P2O7:Tb3+, R (R = Eu2+, Ce3+) phosphors for white LED

The Ba2P2O7:Tb3+, R (R = Eu2+, Ce3+) phosphors were synthesized by use of a co-precipitation method. Crystal phase, excitation and emission spectra of sample phosphors are analyzed by means of XRD and FL, respectively. The emission spectra of Ba2P2O7:Ce3+, Tb3+ phosphors exhibit four linear peaks attributed to the 5D4 → 7FJ (J = 6–3) transition of Tb3+ while four broad emission bands are observed in the emission spectra of Ba2P2O7:Eu2+, Tb3+ phosphors. The effects of Eu2+ concentration on the luminescent properties of Ba2P2O7:Tb3+, R (R = Eu2+, Ce3+) are studied. Ce3+ affects the luminescent properties of Ba2P2O7:Ce3+, Tb3+ phosphors just as the sensitizer. However, Eu2+ is considered both as the sensitizer and the activator in Ba2P2O7:Eu2+, Tb3+ phosphors. The chromaticity coordinates of Eu2+ and Tb3+ co-doped phosphors gather around the white light field with the CCT approximate to 5000 K, indicating that the luminescent property of Ba2P2O7:Eu2+, Tb3+ phosphors may approach to a desired level needed for white LED application.

Influence of Eu substitution for Gd on the structure and photoluminescent properties of (Gd1−xEux)2Ti2O7 pyrochlore solid solutions

This paper presents a study of the synthesis and structural properties of the pyrochlore-type titanates (Gd1−xEux)2Ti2O7. Six compositions with 0≤x≤1 were prepared by solid-state reaction with thermal treatments at 1000 and 1200°C under atmospheric pressure conditions. All the products were systematically characterized by X-ray powder diffraction (XRD), Raman spectroscopy, photoluminescence (PL) and photoluminescent excitation spectra (PLE). Structural refinements of X-ray powder diffraction data using Rietveld method show that all compounds of the (Gd1−xEux)2Ti2O7 solid solution crystallize in a pyrochlore structure. The lattice parameters increase linearly with increasing Eu content in agreement with Vegard's rule. PL spectra show that the characteristic peaks correspond to the f–f transition 5D0–7FJ (J=1, 2, 3 and 4) of Eu3+. The effect of Eu3+ ions concentration on the optical properties, namely, photoluminescence emission, is measured and discussed. The oxides exhibit higher PL intensity with the Eu3+ ion concentration and strong orange emission at 589nm (5D0–7F1) corresponding to the magnetic dipole transition.

Yb3 +,Er3 +,Eu3 +-codoped YVO4 material for bioimaging with dual mode excitation

We propose an efficient bioimaging strategy using Yb3+,Er3+,Eu3+-triplet doped YVO4 nanoparticles which were synthesized with polymer as a template. The obtained particles possess nanoscale, uniform, and flexible excitation. The effect of Eu3+ ions on the luminescence properties of YVO4:Yb3+,Er3+,Eu3+ was investigated. The upconversion mechanism of the prepared material was also discussed. The structure and optical properties of the prepared material were characterized by using X-ray diffraction (XRD), Fourier-transform IR spectroscopy (FTIR), scanning electron microscopy (SEM), Transmission electron microscopy (TEM) upconversion and photoluminescence spectra. The Commission International de I′Eclairage (CIE) chromaticity coordinates was investigated to confirm the performance of color luminescent emission. The prepared YVO4:Yb3+,Er3+,Eu3+ nanoparticles could be easily dispersed in water by surface modification with cysteine (Cys) and glutathione (GSH). The aqueous dispersion of the modified YVO4:Yb3+,Er3+,Eu3+ exhibits bright upconversion and downconversion luminescence and has been applied for bioimaging of HeLa cells. Our developed material with dual excitation offers a promising advance in bioimaging.

Tuning of photoluminescence emission properties of Eu3+ doped Gd2O3 by different excitations

In this work, we investigated cubical particles of europium doped gadolinium oxide based material for colour tuning by different excitations. Structural properties of the material were studied by transmission electron microscopy and X-ray diffraction analysis. The Photo-luminescence (PL) technique was used to study luminescent properties of the material and its optical features were thoroughly investigated by calculating CIE chromaticity. Effect of Eu3+ concentration on emission spectra for three excitations was also recorded. The emission intensity for 613nm, 584nm and 467nm were recorded as the function of dopant ion concentration. It was observed that the blue emission quenched at 1mol% Eu3+ whereas red and green quenched after 2mol% of Eu3+.

Synthesis and optical properties of Eu3+‐substituted glaserite‐type orthovanadates CsK2Y[VO4]2

A new Eu3+ -substituted CsK2 Y[VO4 ]2 glaserite-type orthovanadate phosphor was synthesized by the conventional high temperature solid-state reaction method. The phase purity was confirmed by powder X-ray diffraction study and it reveals that all the compositions crystallize in the hexagonal structure. The morphology and elemental composition were measured by FE-SEM with Energy Dispersive Analysis Of X Rays (EDAX). The band gap is determined by diffuse reflectance spectra. The self-activated luminescence of the host and Eu3+ -substituted luminescence behaviours were studied in detail by photoluminescence spectra. The host CsK2 Y[VO4 ]2 shows green emission, whereas the Eu3+ -substituted compositions show red emission. Effect of Eu3+ concentrations on the photoluminescence behaviour were also been studied. The Eu3+ -doped samples show not only several sharp emission lines but also a broad emission band due to presence of the [VO4 ]3- in the host, which clearly indicates that there is incomplete energy transfer from (VO4 ) charge transfer band to Eu3+. The life time of the phosphors also been studied. The Commission Internationale de l'Eclairage (CIE) chromaticity colour coordinates were calculated and it is very much closer to the National Television Standard Committee (NTSC) standards. These investigations evidently reveal that the self-activated and Eu3+ -activated phosphors show a great potential applications as a red phosphor for solid-state lighting includes white light-emitting diodes (wLEDs).

Novel MgTiO3:Eu3+ Nanophosphor Its Photometric Analysis for Multifunctional Applications

MgTiO3:Eu3+ (1-11 mol%) nanophosphors were synthesized by a facile solution combustion process. PXRD studies confirm single phase rhombohedral structure with the space group R-3. The average crystallite size determined by TEM and Scherrer’s method was found to be in the range 20-50 nm. Effects of Eu3+ (1-11 mol%) cations on the luminescence properties of MgTiO3 nanoparticles exhibit intense red emission upon 415 nm near ultra violet (NUV) excitation. The characteristic emission peaks recorded in the range 500-700 nm may be attributed to the 4f–4f intra shell transitions (5D0→7Fj=0,1,2,3) of Eu3+ cations. The CIE chromaticity co-ordinates were calculated from emission spectra and the values (x, y) were very close to NTSC standard values for red emission. Therefore, the present phosphor may be highly useful for solid state display applications and for wLEDs.

Tailoring the structure and thermoelectric properties of BaTiO3via Eu2+ substitution.

A series of Ba1-xEuxTiO3-δ (0.1 ≤ x ≤ 0.9) phases with ∼40 nm particle size were synthesized via a Pechini method followed by annealing and sintering under a reducing atmosphere. The effects of Eu2+ substitution on the BaTiO3 crystal structure and the thermoelectric transport properties were systematically investigated. According to synchrotron X-ray diffraction data only cubic perovskite structures were observed. On the local scale below about 20 Å (equal to ∼5 unit cells) deviations from the cubic structure model (Pm3[combining macron]m) were detected by evaluation of the pair distribution function (PDF). These deviations cannot be explained by a simple symmetry breaking model like in EuTiO3-δ. The best fit was achieved in the space group Amm2 allowing for a movement of Ti and Ba/Eu along 〈110〉 of the parent unit cell as observed for BaTiO3. Density functional calculations delivered an insight into the electronic structure of Ba1-xEuxTiO3-δ. From the obtained density of states a significant reduction of the band gap by the presence of filled Eu2+ 4f states at the top of the valence band was observed. The physical property measurements revealed that barium-europium titanates exhibit n-type semiconducting behavior and at high temperature the electrical conductivity strongly depended on the Eu2+ content. Activation energies calculated from the electrical conductivity and Seebeck coefficient data indicate that at high temperatures (800 K < T < 1123 K) the conduction mechanism of Ba1-xEuxTiO3-δ (0.1 ≤ x ≤ 0.9) is a polaron hopping when 0 < x ≤ 0.6 and is a thermally activated process when 0.6 < x < 1. Besides, the thermal conductivity increases with increasing Eu2+ concentration. Due to a remarkable improvement of the power factor, Ba0.1Eu0.9TiO3-δ showed a ZT value of 0.24 at 1123 K.

Hydrothermal assisted synthesis and photoluminescence of (Y1-xEux)2WO6 red phosphors

Phase-pure (Y1-xEux)2WO6 (x = 0.2–0.11) red phosphors (average crystallite size ∼66 nm) in a monoclinic structure have been calcined at 1300 °C from their precursors autoclaved from the mixed solutions of rare-earth nitrate and sodium tungstate dihydrate (Na2WO4·2H2O) at 180 °C and pH∼10, instead of the commonly adopted pH values of 3–7, without the use of any surfactant. The materials were characterized in detail by the combined techniques of XRD, FT-IR, FE-SEM, TEM, EDS, and optical spectroscopy to reveal (1) the phase structure, morphology, and spatial cation distribution of the hydrothermal product, (2) the course of phase and morphology evolution that leads to the targeted tungstate phosphor, and (3) the effects of Eu3+ content on photoluminescence properties, including excitation/emission, asymmetry factor of luminescence (5D0→7F2/5D0→7F1 intensity ratio), fluorescence lifetime, and CIE chromaticity coordinates. Through energy transfer from the [WO6]6− ligands to Eu3+, the (Y1-xEux)2WO6 phosphors exhibit sharp 5D0→7FJ (J = 0–4) emissions upon UV excitation into the O2--W6+ charge transfer band peaked at 327 nm, with the red emission at 611 nm being the most prominent (5D0→7F2 transition of Eu3+). The optimal Eu3+ content was determined to be ∼9 at.% (x = 0.09), and concentration quenching of luminescence was analyzed to be owing to exchange interaction. The emission color moves closer to the red region in the CIE chromaticity diagram with increasing Eu3+ doping, while fluorescence lifetime of the 611 nm emission, analyzed to be around 1.05 ± 0.05 ms, shows weak dependence on the Eu3+ content.

Toward High Energy Resolution in CsSrI3/Eu2+ Scintillating Crystals: Effects of Off-Stoichiometry and Eu2+ Concentration

CsSrI3/Eu2+ has very promising scintillation properties for gamma-ray spectroscopy applications, but it has proven difficult to grow high quality single crystals in large sizes. This paper reports a composition-engineering strategy, in this case a combination of off-stoichiometric melts and Eu2+ concentration optimization, to obtain large-size CsSrI3/Eu2+ crystals with excellent energy resolution. Crystals of a series of off-stoichiometric compositions, Cs(1+x)(Sr,Eu)(1–x)I(3–x) (x = 0, 0.05, 0.06, and 0.1), were grown by the Bridgman method. The Cs1.06Sr0.94I2.94/Eu2+ single crystal has the highest optical transmittance between 450 and 800 nm. Cs1.06Sr0.94I2.94 single crystals doped with 0.5, 1, 3, 5, and 7 mol % Eu2+ ions were also grown by the Bridgman method. The effects of Eu2+ concentration on the phase purity and optical and scintillation properties were studied. X-ray diffraction patterns confirmed the phase purity of all samples with the exception of a hydrate phase formed during measurement. Inc...

Thermoluminescent response and kinetic parameters of Eu3+-doped LiF crystals exposed to X-rays

In the present work pure and Eu3+-doped LiF crystals were synthesized through co-precipitation method and the effect of Eu3+ concentration on the thermoluminescent (TL) response is reported. A cubic crystalline phase was determined by XRD for all synthesized samples. The photoluminescence spectra as well as UV–vis absorbance were also analyzed and four emissions bands centered at 592nm (5D0 → 7F1), 614nm (5D0 → 7F2), 652nm (5D0 → 7F3) and 698nm (5D0 → 7F4) have been observed. The TL response to X-ray irradiation was studied for an exposition of 43R during a total time of 52s. The presence of Eu3+ in the samples enhanced the TL signal, due to the Eu3+ ions that are incorporated into the LiF crystalline lattice which promotes the formation of defects in the unit cell. The kinetic parameters (E, b, s) were calculated using the glow-curve shape method. Energy traps around E=1eV and frequency factors on the order s=108s−1 were obtained on average, regardless of the Eu3+ concentration. The host of LiF showed the higher characteristic energies and frequency factors, respectively. The 1.0mol% Eu3+-doped sample was found to have a sensitivity 5 times greater than the host of LiF. The good TL sensitivity to X- ray exhibited by the Eu3+-doped LiF crystals synthesized in this work, suggests that this material should be further studied with respect to other characteristics before being used as a radiation dosimeter.

Concentration- and temperature-dependent fluorescent quenching and Judd–Ofelt analysis of Eu3+ in NaLaTi2O6 phosphors

A series of NaLaTi2O6: Eu3+ red phosphors with different Eu3+ ion concentrations were prepared via a high-temperature solid-state reaction technique. The effects of Eu3+ ion concentration and temperature on the fluorescent properties of NaLaTi2O6: Eu3+ phosphors were investigated. The XRD patterns revealed that the as-synthesized samples were single-phase NaLaTi2O6. Eu3+ ion concentration-dependent excitation and emission spectra showed that there was an efficient energy transfer from NaLaTi2O6 host to Eu3+ ions. Concentration quenching was observed and can be ascribed to exchange interaction between Eu3+ ions based on Van Uitert’s model. According to the temperature-dependent emission spectra and the fluorescence decay curves, crossover process was confirmed to be the main mechanism for the temperature-dependent fluorescence quenching behavior of 5D0 level of Eu3+ ions in NaLaTi2O6 phosphors. The activation energy was obtained to be 0.30 eV by Arrhenius model. Based on the emission spectra and Judd–Ofelt theory, the optical transition properties of Eu3+ ions in NaLaTi2O6 phosphors were studied.

Synthesis and characterization of Mg2SiO4:Tb3+, Eu3+ phosphors for white light generation

The effect of Eu3+ codoping on the structural, morphological, and optical properties of Mg2SiO4:Tb3+ was investigated. The phosphor powders were synthesized by changing the molar concentration of Eu3+ at a fixed Tb3+ content of 5 mol% by using a conventional solid-state reaction. The X-ray diffraction patterns revealed that the crystal structure of all the phosphors, irrespective of the Eu3+ and the Tb3+ contents, showed an orthorhombic structure, and the surface morphology exhibited pebble-like crystalline grains. The emission spectra of Eu3+ and Tb3+-codoped Mg2SiO4 phosphors under an ultraviolet excitation of 252 nm consisted of one intense red band at 619 nm and five weak bands at 448, 488, 598, 658, and 707 nm originating from the transitions of Eu3+, in addition to the several emission bands located at 492, 552, 592, and 628 nm arising from the transitions of Tb3+. As the Eu3+ content was increased, the intensity of the main green emission band at 552 nm decreased markedly and disappeared at 10 mol% Eu3+, when complete energy transfer from Tb3+ to Eu3+ was observed. The results suggest that the emission wavelength and the luminescent intensity of the phosphors can be tuned by modulating the Eu3+ and the Tb3+ contents incorporated into the host matrix.

Eu-doped Si-SiO2 core–shell nanowires for Si-compatible red emission

The indirect bandgap of single-crystalline silicon has so far precluded the full integration of silicon microelectronics with photonics—which is expected to allow the realization of low-cost, high-speed optical information processing and communication in the future. Here we report the growth of europium (Eu)-doped Si-SiO2 core–shell nanowires by an oxide-assisted chemical vapor deposition method. The Eu concentration in these nanowires is effectively improved by intentionally increasing the thickness of SiO2 shells. As a result, a strong Si-compatible red emission from Eu3+ ions was observed under laser illumination. The effect of Eu3+ concentration on the emission efficiency was comprehensively studied, with the highest efficiency at Eu content about 0.8 at%. The relaxation mechanism of this concentration dependent luminescence was further explored through lifetime measurements. In light of the strong characteristic red emission and nanoscale footprint, these nanowires are promising Si-compatible light emission materials for future integrated nanophotonics.

Usefulness of pancreaticoduodenectomy with splenic artery resection (PDSAR) for borderline resectable/locally unresectable pancreatic head carcinoma

We report here the effect of Eu2+ concentration in KCa0.8Sr0.2I3:Eu2+ single crystal scintillators. KCa0.8Sr0.2I3:Eu2+ single crystals doped with 0.5, 1, 3, 5, and 7 mol% Eu2+ were grown by the Bridgman method. The effects of varying Eu2+concentration and crystal volume on the scintillation properties, including light yield, energy resolution, nonproportionality, scintillation decay time and afterglow level, were systematically investigated. For 5 mm×5 mm×5 mm samples, the best light yield of 86,000±4000 photons/MeV was achieved with a content of 5 mol% Eu2+; its energy resolution of 2.5% at 662 keV was comparable to that of LaBr3:Ce3+ and SrI2:Eu2+. With larger samples of about 2.2 cm3, the best performances achieved were for 3 mol% Eu2+ concentration, i.e. a light yield of 76,000±4000 photons/MeV and an energy resolution of 3% at 662 keV. A direct correlation between nonproportionality and Eu2+ concentration was found. A continuous lengthening of scintillation decay time and x-ray induced afterglow level with increasing Eu2+ concentration was observed. The self-absorption effect was evaluated by using the Stokes shift and the temperature dependence of the photoluminescence decay (PL) of the Eu2+ centers. The sample with the highest dopant concentration had more severe temperature quenching of the Eu2+5d-4f emission than the sample with the lowest dopant concentration, which could be ascribed to the thermally activated concentration quenching.

Tailoring the luminescence of Eu3+ co-doped Dy3+ incorporated aluminofluoro-borophosphate glasses for white light applications

Co-doping of Eu3+ ions in Dy3+ single doped glasses improves white light emission. This manuscript reports correlation between the structural rearrangement and its effect on the optical properties of the title glasses. The nephelauxetic effect on absorption transitions have been used to elucidate the bonding nature of the RE3+ ions with their surrounding ligands. It reveals the predominant ionic nature of the dysprosium bonds while that of Eu ions exhibit covalent nature. Effect of Eu3+ ions on the symmetry of the ligand field around the Dy3+ ions have been predicted using JO theory and asymmetric (Y/B) intensity ratio. It is found that asymmetry around Dy3+ ions increases with Eu3+ ions concentration. Tuneable nature of the white light emission from the Eu3+/Dy3+ co-doped aluminofluoro-borophosphate glasses was confirmed through the CIE 1931 chromaticity coordinates for glasses containing different concentrations of europium. The energy transfer process takes place between Dy3+ and Eu3+ ions has also been confirmed through lifetime measurements. Fitting the decay curves using IH model thus reveal the dipole–dipole nature of interaction.

Photoluminescence properties of LiTi2 - x Eux (PO4 )3 phosphor.

A solid-state reaction route-based LiTi2 - x Eux (PO4 )3 was phosphor synthesized for the first time to evaluate its luminescence performance by excitation, emission and lifetime (τ) measurements. The LiTi2 - x Eux (PO4 )3 phosphor was excited at λexci. = 397 nm to give an intense orange-red (597 nm) emission attributed to the 5 D0 → 7 F1 magnetic dipole (ΔJ = ±1) transition and red (616 nm) emission (5 D0 → 7 F2 ), which is an electric dipole (ΔJ = ±2) transition of the Eu3+ ion. Beside this, excitation and emission spectra of host LiTi2 (PO4 )3 powder were also reported. The effect of Eu3+ concentration on luminescence characteristics was explained from emission and lifetime profiles. Concentration quenching in the LiTi2 - x Eux (PO4 )3 phosphor was studied from the Dexter's model. Dipole-quadrupole interaction is found to be responsible for energy transfer among Eu3+ ions in the host lattice. The LiTi2 - x Eux (PO4 )3 phosphor displayed a reddish-orange colour realized from a CIE chromaticity diagram. We therefore suggest that this new phosphor could be used as an optical material of technological importance in the field of display devices. Copyright © 2016 John Wiley & Sons, Ltd.

Strong red-emission of Eu3+:Li4Ti5O12 powders for phosphor applications

The synthesis and photoluminescence properties of trivalent europium doped lithium titanate (Eu3+:Li4Ti5O12) with different Eu3+ concentrations (0.1mol%, 0.3mol%, 1.0mol%, 3.0mol%) are reported and analyzed as a phosphor. Europium (III) nitrate (Eu(NO3)3) was employed as Eu3+ source, while lithium acetate dihydrate (CH3COOLi·2H2O) and titanium n-butoxide (Ti(OC4H9)4) were adopted as raw materials to synthesize the host lithium titanate with a Li:Ti stoichiometry of 4.5:1. Phase identification was performed using X-ray diffraction (XRD), and morphology was examined using scanning electron microscopy (SEM). Eu3+:Li4Ti5O12 powders showed strong red emission at 612nm, corresponding to the 5D0–7F2 transition, with the strongest excitation peak observed in the blue light region at 464nm. Decay time analyses revealed relatively short lifetimes accompanying typical exponential decay rates. The effect of Eu3+ concentration (0.1mol%, 0.3mol%, 1.0mol%, 3.0mol%) on photoluminescence intensity and decay time was explored, and is reported here. It was determined that the CIE color coordinates (0.66, 0.34) of the doped Li4Ti5O12 powders were independent of Eu3+ concentration, and that the coordinates are very similar to the ideal red chromaticity (0.67, 0.33) designated by the National Television Standard Committee (NTSC) system.