J. Phys. Chem. C 2009, 113, 10767–10772
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Luminescent Properties of Y2(MoO4)3:Eu3+ Red Phosphors with Flowerlike Shape Prepared via Coprecipitation Method Yue Tian,†,‡ Xiaohui Qi,† Xiaowei Wu,† Ruinian Hua,*,† and Baojiu Chen*,‡ College of Life Science, Dalian Nationalities UniVersity, Dalian, 116600, China, and Department of Physics, Dalian Maritime UniVersity, Dalian, 116026, China ReceiVed: February 5, 2009; ReVised Manuscript ReceiVed: April 9, 2009
Novel Y2(MoO4)3:Eu3+ red phosphors were synthesized through a simple coprecipitation process and characterized by using X-ray diffraction (XRD), field emission scanning electron microscopy (FE-SEM), and fluorescent spectrophotometry. The results of XRD and FE-SEM show that resultant samples are single phase and have flowerlike shape. In the excitation spectra of Y2(MoO4)3:Eu3+ phosphors, by monitoring 616 nm, the charge transfer bands (CTB) of Eu3+fO2- and Mo6+fO2- centering at around 264 and 310 nm can be observed, respectively. Moreover, the intensity ratio of charge transfer band between Eu3+fO2- and Mo6+fO2increases with increasing Eu3+ ions doping concentration. The characteristic red emission at around 616 nm of Eu3+ ions is also observed, ascribed to the 5D0f7F2 transition of Eu3+ ions, and the optimal doping concentration is 12 mol %. Finally, the Ωλ (λ ) 2 and 4) intensity parameters and Huang-Rhys factor were also calculated according to Judd-Ofelt theory and multiphonon relaxation theory, respectively. 1. Introduction Rare earth (RE) ion doped phosphors have attracted great interest during the past several decades due to their unique physical and chemical properties.1-3 RE ions can display many significative properties in optics, electronics, and magnetics, originating from f-f electronic transitions within the 4f shell. Among these RE ions, the Eu3+ ion is an important activator that can emit red fluorescence centered at around 612 nm, corresponding to the 5D0f7F2 transition, while located in a noncentrosymmetric site. Thus, many materials doped with Eu3+ can be used as red phosphors and have potential application in color television displays.4 Molybdates are important inorganic compounds and display some excellent performance in the field of catalysis, lasers, and ionic conductors.5-7 Lately, many works focused on luminescence properties research of molybdates doped with rare earth ions also have been carried out.8-11 The optical properties of molybdates are structure-dependent. In addition, molybdates can exist in different crystal phases composed of the same or different valences of molybdenum element. The formation of different phase structures depends on the preparation approach, the pH value of the reaction system, and the stoichiometric ratio of starting materials. Nowadays, many methods also have been developed to synthesize molybdates, for example, a hightemperature solid-state reaction,8 a sol-gel process,11 a freezedried precursor method,7 and a hydrothermal process.9 However, to our best knowledge, there is no report on preparing molybdates using a coprecipitation method. The coprecipitation method is a simple method and has been widely used to prepare luminescent materials. It has many advantages over other methods, such as simple equipment, short time period, and simple operation. Recently, molybdates also have been widely studied as host candidates for white-light-emitting diodes (LEDs) * Corresponding author. Tel. +86-411-87633470. Fax: +86-41187656217. E-mail:
[email protected]. † Dalian Nationalities University. ‡ Dalian Maritime University.
because of some special properties of the MoO42- group.8 Having many advantages over the traditional incandescent and fluorescent lights in light efficiency, energy consumption, service longevity, and environmental conservation, white LEDs are considered the next generation lighting resource and have evoked much attention since the first white LEDs had become commercially available in 1997 by combining a blue-lightemitting GaN chip with yellow YAG:Ce3+ phosphors.12 Nowadays, most commercially available white LEDs are produced on the basis of the combination of yellow phosphor and blue GaN chip. However, the YAG:Ce3+ yellow phosphors lack a sufficient red emission component. Therefore, the obtained white light displays a poor color rendering index (CRI) and the efficiency of light conversion is also low. As may be expected, the CRI and light conversion can be greatly improved by combining a small amount of red phosphors with YAG:Ce3+. Accordingly, it is an attractive and challenging research task to develop novel, stable, and inorganic RE ions doped red phosphors that can be excited effectively by the near UV or blue LEDs. On the basis of the above reasons, in this work, we synthesized Eu3+ ion doped Y2(MoO4)3 phosphors using a coprecipitation method for the first time and studied their photoluminescence properties. Furthermore, we calculated Ωλ (λ ) 2, 4) intensity parameters and the quantum efficiency of the 5D0 level according to Judd-Ofelt (J-O) theory. Simultaneously, a phonon sideband was also observed in the phosphors. The chromaticity coordinates (x, y) at room temperature for Y2(MoO4)3:Eu3+ phosphors are x ) 0.656 and y ) 0.344, suggesting that it has high color saturation. Therefore, Y2(MoO4)3: Eu3+ phosphors may become a potential red phosphors for white LEDs. 2. Experimental Section 2.1. Synthesis. All reagents used in this work are analytical grade without any further purification except for Eu2O3 and Y2O3 (spectrographically pure). Eu(NO3)3 · 6H2O and Y(NO3)3 · 6H2O were prepared through dissolving Eu2O3 and Y2O3 in nitrate acid
10.1021/jp901053q CCC: $40.75 2009 American Chemical Society Published on Web 05/27/2009
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Figure 1. The XRD patterns of (a) Y2(MoO4)3:12 mol % Eu3+ and (b) Y2(MoO4)3:30 mol % Eu3+ phosphors.
(the volume ratio between nitrate acid and water is 1:1). Then, the resultant solutions were recrystallized three times. Lastly, the Eu(NO3)3 · 6H2O and Y(NO3)3 · 6H2O were obtained when white multicrystal powders were well dried in vacuum at 90 °C for 12 h. Y2(MoO4)3:Eu3+ red phosphors were synthesized via a simple coprecipitation method. The detailed process was as follows: First, 0.001 mol (0.3863 g) of Y(NO3)3 · 6H2O, 5 × 10-5mol (0.0223 g, 5.0 mol % Eu3+) of Eu(NO3)3 · 6H2O, and 0.0015 mol (0.3279 g) of Na2MoO4 · 2H2O were dissolved in 20 and 50 mL of distilled water and were labeled as A and B solution, respectively. Second, A solution was dropped in B solution slowly under magnetic stirring, and then a white precipitate formed at once. After reacting for 30 min, the precursor solution was centrifuged at 4500 rpm for 20 min. The resultant white precipitate was washed three times with distilled water and dried at 80 °C. Finally, the Y2(MoO4)3: Eu3+ red phosphors were obtained when resultant precursors were calcined at 900 °C for 1 h. 2.2. Characterization. The phase purity and crystallinity of the samples were examined by using powder X-ray diffraction (XRD) performed on an XRD-6000 (Shimadzu) diffractometer by using Cu KR1 radiation (λ ) 0.154 06 nm). The XRD data were collected by using a scanning mode in the 2θ range from 10° to 70° with a scanning step of 0.02° and a scanning rate of 2.0° min-1. Silicon was used as an internal standard. The particle size, shape, and morphology were examined by using field emission scanning electron microscopy (FE-SEM) (Hitachi S-4800) with accelerating voltage of 10 kV. Photoluminescence (PL) emission, excitation spectra were recorded with a Hitachi F-4600 spectrophotometer equipped with a 150 W xenon lamp as excitation source. All measurements were carried out at room temperature.
Tian et al. 3. Results and discussion 3.1. Structural and Morphology Characterization of the Products. In order to characterize the phase purity and crystallinity of the samples, the XRD patterns for all products were measured. Among these samples, the XRD patterns of Y2(MoO4)3:xEu3+ phosphors with x ) 12 and 30 mol % are shown in Figure 1 as representatives. All the samples doped with low Eu3+ concentration display the same diffraction patterns, which appeared in JCPDS card No. 28-1451, corresponding to the intrinsic diffraction patterns of Y2(MoO4)3. In addition, no peaks of impure phases are observed. This fact suggests that the resultant powders are pure and single phase. However, the diffraction patterns of Eu2(MoO4)3 are detected when the Eu3+ ion doping concentration in Y2(MoO4)3 matrix exceeds 30 mol % (Figure 1b). Figure 2 exhibits the FE-SEM images for Y2(MoO4)3:Eu3+ phosphors doped with 5 and 12 mol % Eu3+ concentration as representatives. It can be found that each phosphor particle has regular morphology and flowerlike shape. The phosphor particles are composed of a large number of flakes. The thickness of the flakes is estimated to be 30 nm, and the average size of two large surfaces is around 4 µm. Each phosphor particle is built by the flakes intersected each other. 3.2. Photoluminescent Properties. The excitation spectrum of Eu3+ ion doped Y2(MoO4)3 phosphor while monitoring 616 nm emission corresponding to the 5D0f7F2 transition is shown in Figure 3. It can be seen that the excitation spectrum consists of two parts: one is an intense, broad band from 230 to 350 nm, another is sharp lines from 350 to 500 nm. The intense, broad band can be decomposed into two Guassian components, A and B. The location of peak A is around 264 nm, which is assigned to the charge transfer (CT) band of Eu3+fO2-. While that of peak B is around 310 nm, corresponding to the CT band of Mo6+fO2-. The broad bands in the UV region may contain the charge transfer excitation of Eu3+ ions and the energy-transfer transition from molybdate groups to Eu3+ ions. In most of the literature, the contribution of the two components cannot be distinguished due to spectral overlap.13,14 The CT band corresponds to the electronic transition from the 2p orbital of O2- to the 4f orbital of Eu3+, and it is related closely to the covalency between O2- and Eu3+ and coordination environment around Eu3+. The decrease in energy for electron transfer in O2- to Eu3+ represents the increase in the covalency and the decrease in ionicity between oxygen and Eu3+. The sharp lines correspond to the characteristic fff transitions of Eu3+ ions within its 4f6 configuration. They are ascribed to 7 F0f5D4, 7F0f5GJ,5L7, 7F0f5L6, 7F0f5D3, and 7F0f5D2 transitions of Eu3+ ion, respectively. Figure 4 shows the excitation spectra of Y2(MoO4)3 powders doped with different Eu3+ ion concentrations. It can be seen that the relative contribution of the two components, peaks A and B, has remarkable variation as the concentrations of
Figure 2. The FE-SEM images of Y2(MoO4)3:5 mol % Eu3+ and (a) and Y2(MoO4)3:12 mol % Eu3+ phosphors.
Luminescent Properties of Y2(MoO4)3:Eu3+
Figure 3. The excitation spectrum of Y2(MoO4)3:12 mol % Eu3+ phosphors (λem ) 616 nm).
Figure 4. Excitation spectra of Y2(MoO4)3 doped with different Eu3+ ion concentrations (λem ) 616 nm): (a) 1 mol %, (b) 10 mol %, (c) 17 mol %, and (d) 25 mol %.
Figure 5. The emission spectrum of Y2(MoO4)3:12 mol % Eu3+ phosphors (λex ) 394 nm). The insert shows the 5D1f7FJ (J ) 0-2) transition of Eu3+ ion.
Eu3+ ions varies. The higher concentration of europium leads the relative contribution at shorter wavelength to increase. As a result, the excitation maximum shifts to blue with the increasing europium concentration. Figure 5 displays the emission spectrum of Eu3+ ion doped Y2(MoO4)3 phosphors excited under 395 nm near UV light. As can be seen, the emission spectrum essentially consists
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Figure 6. The relationship of between Eu3+ ion concentration and emission intensity of the Y2(MoO4)3:Eu3+ phosphors under 394 nm excitation.
of intense and sharp lines ranging from 570 to 750 nm, which are attributed to the 5D0f7FJ (J ) 0-4) transitions. Although no emission corresponding to molybdate is observed, the presence of an absorption band originating from the molybdate group is detected in the excitation spectrum when monitoring 616 nm emission. This fact suggests that the energy absorbed by the MoO42- group is transferred to Eu3+ ions levels nonradiatively. That is, the emission corresponding to Eu3+ ions has been observed under excitation of the CT band of the MoO42- group. This process has been known as host-sensitized energy transfer.1 However, the intensity of Eu3+ emission is stronger with CT band excitation when compared to that due to Eu3+ ion excitation. This fact reveals that the energy transfer from the MoO42- group is very efficient. The electric dipole allowed transition would be dominant when Eu3+ ion occupied the lattice site of noncentrosymmetric environment in the scheelite phases according to electronic transition selection rules.2 For this reason, the intensity of 5D0f7F2 (electric dipole transition) was found to be much stronger than that of 5D0f7F1 (magnetic dipole transition). The major emission of Y2(MoO4)3:Eu3+ phosphors is located at 616 nm, which is red. Moreover, the O/R ratio (emission intensity ratio of 5D0f7F1 to 5D0f7F2) was calculated by deconvoluting the emission spectra using a linear combination of multiple Guessian functions. The ratio is found to be 0.12. Compared with YBO3:Eu3+ phosphors, the smaller ratio also implies that Eu3+ ions are located at a noninversion symmetry site.15,16 In addition, other emission of Eu3+ ions correspond to the transitions from excited state 5 D1 to the states 7FJ, which are located in the region 500-570 nm (seen in Figure 5 as an inset). 3.3. Concentration Quenching and Energy Transfer. The doping concentration of luminescent centers is an important factor influencing the phosphor performance.16 Therefore, it is necessary to confirm the optimum doping concentration. The integrated emission intensities of 5D0f7FJ (J ) 0-4) transitions of Y2(MoO4)3 phosphors doped with various Eu3+ ion concentrations were calculated, and the dependence of the emission intensity from the 5D0f7F2 hypersensitive transition of Eu3+ ion doped Y2(MoO4)3 phosphor is shown in Figure 6. The intensity enhances with the increase of doping concentration and reaches a maximum at 12 mol % Eu3+ ion doping concentration. The concentration quenching occurs at a higher concentration. Blasse et al. proposed that the quenching mechanism was associated with the exchange interaction, which
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Figure 7. The relation of the concentration of Eu3+ ions (log C) and the log(I/C) for the 5D0f7F2 transition in Y2(MoO4)3 phosphors.
results in the energy transfer and ultimately quenches the emission from the 5D0 level of the Eu3+ ion.17,18 In this work, we also calculated to prove the energy transfer type of Eu3+ ions in Y2(MoO4)3 phosphors. Huang’s previous study has developed a theoretical description for the relationship between the luminescent intensity and the doping concentration.19 Recent experimental results by Ou-Yang,20 Li,21 and Meng22 have shown an agreement with the theoretical description. According to the Huang’s results, the relationship between luminescent intensity I and doping concentration C could be expressed as
I ∝ a(1-s/d)Γ(1 + s/d)
(1)
a ) CΓ(1 - d/s)[X0(1 + A/γ)]d/s
(2)
where γ is the intrinsic transition probability of sensitizer, s is index of electric multipole, for electric dipole-electric dipole, electricdipole-electricquadrupole,andelectricquadrupole-electric quadrupole interaction; s ) 6, 8, 10, respectively. If s ) 3, the interaction type is an exchange interaction. d is a dimension of the sample; here d ) 3, since the energy transfer between Eu3+ ions inside the particles is considered. A and X0 are constants, and Γ(1 + s/d) is a Γ function. From eqs 1 and 2 it can be derived that
( CI ) ) - ds log C + log f
log
(3)
where f is independent of the doping concentration. Figure 7 shows the log(I/C)-log(C) plots for the 5D0f7F2 transition of Eu3+ ions in the Y2(MoO4)3 phosphors. According to eq 3, using linear fittings to deal with the experimental data in the region of high concentrations, the values of the slope parameter -s/d were obtained to be -1.3 (close to 1), corresponding to s ) 3. This means that the exchange interaction mechanism is dominant for the energy transfer among Eu3+ ions in the Y2(MoO4)3 phosphors. 3.4. Calculation of Ωλ Parameters and Quantum Efficiency of the 5D0 Level. To understand the effect of chemical environment on luminescent properties of Eu3+ ions better, J-O theory was utilized to analyze the transition intensity parameter of Eu3+ ions. In the case of Eu3+ ions, it is possible to determine
Figure 8. Room temperature fluorescence decay curve of Y2(MoO4)3: Eu3+ phosphors (λex ) 394 nm, λem ) 616 nm).
the Ωλ (λ ) 2, 4, 6) parameters from emission spectra. The magnetic dipole transition rate of the 5D0f7F1 can be expressed as
Amd )
64π4kmd3
3h(2J + 1)
n3Smd
(4)
where kmd is the transition energy of the 5D0f7F1 transitions in wavenumber and h is Planck’s constant, 6.626 × 10-27. The factor n is the refractive index of host, and an average index of n equal to 1.5 is used.23 2J′ + 1 is the degeneracy of the initial state (1 for 5D0), and Smd is a constant independent of the host; here it is 7.83 × 10-42.24 The 5D0f7FJ (J ) 2, 4, 6) transition are an electric dipole transition; therefore, the radiation rate can be written as25,26
AJ )
64π4e2k3 n(n2 + 2)2 Ωλ〈ψJ|Uλ |ψJ〉2 9 3h(2J + 1) λ)2,4,6
∑
(5) where e is the electric charge, k is the transition energy of electric dipole transitions in cm-1, Ωλ is the intensity parameter, and ΨJ |Uλ|Ψ′J ′2 values are the squared reduced matrix elements, whose values are 0.0032 and 0.0023 for J′ ) 2 and 4, respectively.27,28 All parameters are used in equations with Gaussian units for convenient calculation. Therefore, eq 5 also can be described by
AJ )
64π4e2k3 n(n2 + 2)2 Ωλ〈ΨJ|Uλ |Ψ′J′〉2 3h(2J′ + 1) 9
(6)
The transition intensity ratio between electronic dipole and magnetic dipole can be expressed by
∫ IJ(k) dk AJ e2kJ3 (n2 + 2)2 ) Ω〈ψJ|Uλ |ψJ〉2 ) 3 2 A k 9n md md ∫ Imd(k) dk (7) The value of (∫IJ(k) dk)/(∫Imd(k) dk) can be gained from the integral area of the emission spectra. So Ωλ can be calculated
Luminescent Properties of Y2(MoO4)3:Eu3+
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TABLE 1: J-O Parameters for Y2(MoO4)3:Eu3+ and CaMoO4:Eu3+ Phosphors compds Y2(MoO4)3:Eu CaMoO4:Eu3+
3+
AR (s-1)
ANR (s-1)
Ω2 (10-20 cm2)
Ω4 (10-20 cm2)
τ (ms)
η
ref
406.9 258.6
1141.2 1766.4
8.90 4.55
0.54 0.78
0.55 0.494
22.38 12.78
this work 9
on the basis of the analysis of the emission spectra. However, the Ω6 intensity parameter is not included in this calculation, since the 5D0f7F6 transition could not be observed. The fluorescent decay curve of the 5D0 level of Eu3+ ions in Y2(MoO4)3:Eu3+ phosphors obtained by monitoring the 5D0f7F2 transition is shown in Figure 8. The typical decay curve of Y2(MoO4)3:Eu3+ phosphors can be fitted using the single exponential method, and the equation can be described as
I(t) ) I0e-t/τ
(8)
The fluorescence lifetime τ of Y2(MoO4)3:Eu3+ phosphors is about 0.55 ms. Further, the emission quantum efficiency of the 5 D0 level of Eu3+ ions in Y2(MoO4)3:Eu3+ phosphors can be determined on the basis of the emission spectra and lifetimes of the 5D0 emitting level. The lifetime (τ), radiative (AR), and nonradiative (ANR) rates are related through the equation
1 ) AR + ANR τ
(9)
Eu3+ phosphors (η ) 12.78%), which is due to appreciably decrease in nonradiative decay rates from the 5D0 level. 3.5. Phonon Sideband Spectrum and Calculation of Huang-Rhys Factor. The phonon sideband spectrum (PSB) that monitored the 5D0f7F2 emission at 616 nm is shown in Figure 9. It can be clearly observed that the PSB ranging from 420 to 480 nm is associated with the 7F0f5D2 transition. Previously, two peaks, centered at around 427 and 447 nm with phonon energy at 1867 and 819 cm-1, were observed. They are attributed to the O-Mo-O and Mo-O vibration. Therefore, it can be concluded that Y2(MoO4)3 host has higher phonon energy than other some oxides, such as Y2O3. In addition, the Huang-Rhys factor can be calculated according to eq 11.
{
I1P W1(S, 〈m〉) W1(S, 〈1 + m〉) p g 0 ) ) W0(S, 〈m〉) p Ω4 parameters (Table 1), this suggests that the coordination geometry is such that the higher rank components of these interactions have lesser values than the lower rank ones. Therefore, this might suggest that the site symmetry occupied by the Eu3+ ions in molybdates systems do not have the character of a centrosymmetric chemical environment and this result agrees with the O/R ratio obtained from emission spectrum. It is important to consider that the 5D0f7F2 transition is formally forbidden by electric dipole selection rules and the band related to this hypersensitive transition (∆J ) 2) is absent when the Eu3+ ion lies on a center of inversion. Moreover, the higher emission quantum efficiency is obtained from the Y2(MoO4)3:Eu3+ phosphors (η ) 22.38%) than in CaMoO4:
Figure 9. Phonon sideband spectrum of Y2(MoO4)3:Eu3+ phosphor monitoring the 5D0f7F1 emission at 616 nm.
Figure 10. CIE chromaticity coordinates of YAG:Ce3+, Y2O2S:Eu3+, and Y2(MoO4)3:12 mol % Eu3+ phosphors.
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transition selection rules,25,29 and the multiphonon sideband locates at a higher energy side than the zero-phonon line and it is a process that can produce a phonon. Therefore, p g 0 in eq 11. Raman scattering spectra of sample have a similar spectral profile with phonon sideband spectra, so IPSB ) I1P. In addition, 〈1 + m〉 can also be approximatively treated as 1 because of higher phonon energy at room temperature. Therefore, the Huang-Rhys factor can also be expressed as
S ) IPSB /IZP
(12)
fore, the Y2(MoO4)3:Eu3+ red phosphors may have a potential application for white light emitting diodes. Acknowledgment. This work was partially supported by NSFC (National Natural Science Foundation of China, grant No. 50572102), the Postdoctoral Fund of Dalian Nationalities University (20056110), Joint Program of NSFC-GACAC (General Administration of Civil Aviation of China, Grant No. 60776814), and Natural Science Foundation of Liaoning Province (grant No. 20082139) and Outstanding Young People Foundation of Jilin Province (Grant No. 20040113). References and Notes
where IPSB and IZP are integral intensity of the one-phonon line and zero-phonon line, respectively. So the calculation result shows that the Huang-Rhys factor equals 0.074 based on eq 12. 3.6. Calculation of Color Coordinate. The Commission International del’Eclairage (CIE) chromaticity coordinates of the Y2(MoO4)3 with 12 mol % Eu3+ doping concentration are shown in Figure 10. The chromaticity coordinates (x, y) of Y2(MoO4)3:Eu3+ phosphors are (0.656, 0.344) for the optimum Eu3+ ion doping concentration. In comparison, the chromaticity coordinates of yellow-emitting YAG:Ce3+ phosphors with (0.461, 0.525) are also introduced. The characteristic index shows that the red emitting Y2(MoO4)3:Eu3+ phosphors have higher color saturation, and these chromaticity coordinates also are better than the commercially available Y2O2S:Eu3+ red phosphor used for cathode ray tube (x ) 0.64, y ) 0.34).3 Furthermore, according to its excitation spectrum, the Y2(MoO4)3: Eu3+ phosphors can absorb not only the emission of UV-LEDs (350-410 nm) but also that of blue LEDs (430-470 nm). Thus, it can be used to compensate the red color deficiency of YAG: Ce3+ based white LEDs or create white light by combining with a blue chip and another green phosphor. So, as a red phosphor, Y2(MoO4)3:Eu3+ phosphors may have a potential application for white LEDs. 4. Conclusion In summary, novel Y2(MoO4)3:Eu3+ red phosphors with flowerlike shape were synthesized through a simple coprecipitation process for the first time. The resultant powders were characterized using XRD, FE-SEM, and fluorescence photometry. The charge transfer band intensity ratio between Eu3+fO2and Mo6+fO2- increases with increasing Eu3+ ion doping concentration. Moreover, the efficient red fluorescence, corresponding to the 5D0f7F2 transition of Eu3+ ion, is observed under 394 nm near-UV light excitation. The optimum Eu3+ ion doping concentration is 12 mol % and the energy transfer type among Eu3+ ions in Y2(MoO4)3 phosphors is exchange interaction by theoretical calculation. In addition, the higher Ω2 intensity parameters were obtained on the basis of the emission spectra, suggesting that the Y system is in a more polarizable chemical environment and the metal-donor interaction has stronger covalent character. The photon sideband was also observed, which indicates that Y2(MoO4)3 phosphors have higher phonon energy. The emission quantum efficiency of the 5D0 level of Eu3+ ion in phosphor is 22.38% and the CIE indices are x ) 0.656 and y ) 0.344, which reveal that, as a red phosphor, Y2(MoO4)3:Eu3+ has excellent performance. There-
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