MoO6 Groups Research Articles

Direct mechanochemical synthesis of CaMoO4 and Dy3+ doped CaMoO4 nanoparticles and their photoluminescent properties

Calcium molybdate (CaMoO4) and Dy3+ doped CaMoO4 (Dy3+ = 0.5, 1, 1.5, 2 and 2.5 at.%) nanoparticles were successfully obtained by mechanochemical approach. The influence of Dy3+ ion concentration on the structure, morphology, and photoluminescent properties were investigated. The CaMoO4 and Dy3+ doped CaMoO4 phases with tetragonal structure were completely prepared after 30 min milling time with applied milling speed of 850 rpm. TEM analysis shows that the synthesized samples consist of mainly spherical particles with narrow particle size distribution. According to both XRD and TEM analysis, the average particles size is below 40 nm. The UV–vis absorption spectra show one peak at 240–245 nm. The calculated optical band gap of pure CaMoO4 is 3.96 eV and it decreases to 3.65 eV with increasing the concentration of Dy3+ ion up to 2.5 at %. The excitation spectra of the Dy3+-doped CaMoO4 samples contain absorption peaks corresponding to the MoO4 group and to the Dy3+ ion. The green and blue light emissions were observed for pure CaMoO4 and Dy3+ doped CaMoO4 samples under different wavelengths excitation (250 and 350 nm) typical for absorption of the host matrix. Emission spectra of all doped powders consist of the characteristic peaks of Dy3+ in the blue (∼480 nm) and yellow (∼575 nm) regions which are assigned to the 4F9/2 → 6H15/2 and 4F9/2 → 6H13/2 transitions, respectively. The weak peak at 660 nm also is observed due to 4F9/2 → 6H11/2 transition of Dy3+ ion. The highest photoluminescence emission intensity was detected when the sample is doped with 1.5 at.% Dy3+ concentration. It was found that the color coordinates (x and y) of 1.5 at.% and 2 at.% Dy3+-doped CaMoO4 fall close to the white light region in the CIE diagram. The results indicate that the mechanochemically obtained Dy3+ doped CaMoO4 nanoparticles can find application in different optical instruments.

NaFe2PO4(MoO4)2: A Promising NASICON-Type Electrode Material for Sodium-Ion Batteries.

Searching for polyanionic electrode materials with high Na+ and electronic conductivity is pivotal to realize high-performance sodium-ion batteries. Here, we report a novel polyanionic-based NASICON-type compound, NaFe2PO4(MoO4)2 (NFPM), that does not crystallize in the common space group R-3c or C2/c but in the rare P2/c. The studies on bond valence sum maps show that NFPM has high Na+ conductivity because the large volumes of MoO4 groups make the interstitial channels wider, thus making the energy barrier of Na+ diffusion decrease along these channels. Density functional theory calculations demonstrate that NFPM has high electronic conductivity because the contribution of Mo 4d orbitals on the formation of the bottom of the conduction band makes the connected MoO4 groups take part in electron transport. Electrochemical tests exhibit that NFPM can deliver a capacity of ∼80 mAh g-1 with good reversible cyclability utilizing the Fe3+/Fe2+ redox couple. In situ X-ray diffraction measurements indicate that NFPM undergoes one-phase reaction mechanism in the process of charge and discharge.

Origin of luminescence in ZnMoO4 crystals: Insights from spectroscopic studies and electronic structure calculations

Abstract A set of ZnMoO4 polycrystalline samples was synthesized by solid state reaction method and characterized by XRD structural analysis, ICP elemental analysis, SEM-EDX analysis, UV–Vis diffuse reflectance spectroscopy. The photoluminescence (PL) properties of ZnMoO4 samples were studied in 8–300 K temperature range with use of synchrotron radiation as an excitation source. The geometry-optimized electronic structure calculations of perfect and defective ZnMoO4 crystals were carried out by the DFT-based band-structure methods, plane-wave pseudo-potential (CASTEP program package) and FP-LAPW (Wien2k package). A number of point defects which can influence the luminescence properties of ZnMoO4 was considered in calculations, namely the oxygen vacancy Vo, compensated vacancies Vo + VZn, tungsten impurity WMo and the MoO3-deficient phase Zn3Mo2O9. Comparative analysis of experimental data and calculation results allowed explanation of the origin of the red and blue-green luminescence emission bands of ZnMoO4 as well as formation of their excitation spectra. It is assumed that the green component of ZnMoO4 luminescence emission, like in other molybdates of MIIMoO4 family (MII = Ca, Sr, Cd, Pb) originates from radiative annihilation of excitons self-trapped on regular MoO4 groups. The Red component of ZnMoO4 emission has a defect-related origin and it originates from radiative transitions in MoO4 groups located near oxygen vacancies.

Transition mixed-metal molybdates (MnMoO4) as an electrode for energy storage applications

MnMoO4 nanoparticles were synthesized by employing solvothermal method at optimized experimental condition to explore their electrochemical properties. The fundamental characterization studies such as X-ray diffraction, Raman spectroscopy, and Fourier transform infrared spectra confirmed the formation of pure phase of monoclinic crystal structure with C2/m space group. X-ray photoelectron spectroscopy studies revealed that the core-level Mn-2p spectrum peaks observed at 641.2 eV can be attributed to Mn-2p3/2 and that at 654.1 eV can be indexed to the binding energy of Mn-2p5/2. Major infrared peaks observed at 725, 800, 867, and 946 cm−1 could be designated to the characteristics bands of tetrahedral MoO4 groups in MnMoO4 nanoparticles. Raman peaks observed at 351, 823, 886, and 932 cm−1 corresponded to characteristics bands for MnMoO4 nanoparticles. The cyclic voltammetry studies at different scan rates (i.e., 10, 20, 30, 50, 80, and 100 mV s−1) were performed for all three MnMoO4 nanoparticles and displayed similar redox peaks in the positive and negative current regions, reflecting the pseudocapacitive nature. From galvanostatic charge–discharge profiles, it was found that MnMoO4 nanorods (R2) show high- capacitance of 697.4 F g−1 at 0.5 A g−1 current density and 40% increment in specific capacitance than other nanoparticles and can be considered as suitable nanomaterials as electrode for energy storage applications.

Multi-color luminescence evolution of La2Zr3(MoO4)9:Ln3+ (Ln3+ = Dy3+ and/or Eu3+) nanocrystalline phosphors for UV-pumped white light-emitting devices

Here, we demonstrate a new recreating blue-purple luminescence of La2Zr3(MoO4)9 and host sensitized luminescence in La2Zr3(MoO4)9:Ln3+ (Ln3+ = Dy3+ and/or Eu3+) nanocrystalline phosphors with multi-color luminescence evolution in response to UV light excitation. A series of La2Zr3(MoO4)9 and La2Zr3(MoO4)9:Ln3+ (Ln3+ = Dy3+ and/or Eu3+) nanocrystalline phosphors were synthesized via a citrate sol-gel method. X-ray diffractometer, FE-SEM, HRTEM, diffuse reflection spectra, photoluminescence spectra, and fluorescent decay lifetimes were utilized to characterize the prepared phosphors. The XRD results reveal that the prepared La2Zr3(MoO4)9 and La2Zr3(MoO4)9:Ln3+ (Ln3+ = Dy3+ and/or Eu3+) nanocrystalline phosphors present a single-phased trigonal crystal structure. FE-SEM and HRTEM images indicate that the prepared La2Zr3(MoO4)9:Ln3+ phosphors consist of fine and spherical grains in size of around 35–60 nm in diameter. Under the excitation of ultraviolet light, the La2Zr3(MoO4)9 presents a characteristic broad band emission of MoO4 group from 300 to 550 nm peaking at 399 nm, and the La2Zr3(MoO4)9:Ln3+ (Ln3+ = Dy3+ and/or Eu3+) phosphors show the characteristic emissions of Dy3+ (4F9/2→6H15/2 and 4F9/2→6H13/2 transitions) and Eu3+ (5D0→7FJ transitions, J = 1, 2, 3, and 4), respectively. There exists an energy transfer from La2Zr3(MoO4)9 host lattice to Dy3+ and Eu3+ ions in La2Zr3(MoO4)9:Ln3+ (Ln3+ = Dy3+ and/or Eu3+) phosphor. The luminescence color of La2Zr3(MoO4)9:Ln3+ (Ln3+ = Dy3+ and/or Eu3+) can be tuned from blue-white, white to orange-red by adjusting the doping concentration and the relative ratio of Dy3+ to Eu3+ in La2Zr3(MoO4)9 host lattice. A single-phase white-light-luminescence with high color purity has been realized in La2Zr3(MoO4)9:Dy3+,Eu3+ phosphor. The obtained La2Zr3(MoO4)9:Dy3+,Eu3+ phosphor has potential application in area of UV-pumped white light-emitting devices.

Microwave synthesis and spectroscopic properties of ternary scheelite-type molybdate phosphors NaSrLa(MoO4)3:Er3+,Yb3+

Ternary scheelite-type molybdate NaSrLa(1-x-y)(MoO4)3:xEr3+,yYb3+ (x = y = 0, x = 0.1 and y = 0.2, x = 0.05 and y = 0.45, x = 0.2 and y = 0) phosphors were successfully synthesized by the microwave sol-gel method for the first time. Well-crystallized particles formed after the heat-treatment at 900 °C for 16 h showed a fine and homogeneous morphology with a particle size of 2–3 μm. The crystal structures were refined by the Rietveld method in space group I41/a. The optical properties were examined comparatively using photoluminescence emission and Raman spectroscopy. Under the excitation at 980 nm, the NaSrLa0.7(MoO4)3:0.1Er3+,0.2Yb3+ and NaSrLa0.5(MoO4)3:0.05Er3+,0.45Yb3+ particles exhibited a strong 525-nm emission band, a weaker 550-nm emission band in the green region and weak 655-nm, 490-nm and 410-nm emission bands in the red, blue and violet regions. The pump power dependence and Commission Internationale de L'Eclairage chromaticity of the upconversion emission intensity were evaluated in detail. The presence of Sr in NaSrLa(MoO4)3, in comparison with NaCaLa(MoO4)3 compound, leads to frequency shift mainly in the low region of Raman spectra. The MoO4 bending vibrations are most susceptible to changes in the distance between the nearest oxygen atoms in the nearest neighboring MoO4 groups.

The impact of local structure variation on thermal quenching of luminescence in Ca3MoxW1−xO6:Eu3+ solid solution phosphors

Near-ultraviolet (NUV, 365–410 nm) excitable white light emitting diodes require intense absorption in the NUV region for the tri-color phosphors (red, green, and blue). Optional red phosphor Ca3MoO6:Eu3+ meets the requirement of NUV absorption but suffers from severe quenching, while Ca3WO6:Eu3+ has good resistance to thermal quenching but could not absorb NUV light efficiently. It is requisite to investigate the candidate Ca3MoxW1−xO6:Eu3+ to balance the both effects. Results indicate that thermal quenching turns to be worse with an increase in Mo contents in the solid solutions with inevitable distortions or defects, especially when exciting the charge transfer band of WO6 and MoO6 groups. Temperature-dependent Raman spectroscopy is utilized to reveal the impact of structural variation in the quenching process since the variations influence the energy transfer between WO6/MoO6 groups and Eu3+ ions or among Eu3+ ions. Results show that the tilting or distortion of the Ca/W/MoO6 octahedral framework and weakened Eu3+-O bonds have large impacts on thermal quenching performance of Eu3+ luminescence in the solid solutions. The research would benefit the design of novel red phosphors.

Enhanced frequency upconversion in Ho3+/Yb3+/Li+:YMoO4 nanophosphors for photonic and security ink applications

The YMoO4 nanophosphors codoped with Ho3+/Yb3+/Li+ ions synthesized by the chemical coprecipitation method have been structurally characterized by using X-Ray Diffraction (XRD), Field Emission Scanning Electron Microscopy (FESEM), and Transmission Electron Microscopy (TEM) techniques. The TEM bright field imaging shows that the developed nanophosphors are crystalline in nature with particle size ∼45 nm. The upconversion (UC) emission spectra upon excitation at 980 nm of the nanophosphors at low pump power (<900 mW) show the emission peaks in the UV, green, and red regions, whereas at high pump power (≥900 mW) an intense broad band ranging from 400–900 nm along with a UV band has been observed. The enhancement of about ∼104 times corresponding to the green band in the Ho3+-Yb3+-Li+ codoped nanophosphors compared to that of the Ho3+ singly doped nanophosphors has been observed. This enhancement is caused by the energy transfer from the Yb3+ to Ho3+ ions and modified the local crystal field developed around the rare earth ions. A higher value of the slope (i.e., n ∼ 6.38) for broad band emission within the 944 mW-1200 mW pump power region in the Ho3+-Yb3+-Li+ codoped nanophosphors is found to be due to the involvement of the photon avalanche population process but it is not related to the black body radiation. The intense peak at ∼564 nm and ∼648 nm for the broad band emission is attributed to the charge transfer luminescence of codoped nanophosphors, which is related to the oxygen ion present in the MoO4 group and Yb3+ ion. The observations described in this paper may be of significant interest for developing the visible upconverters, security ink, and novel devices for displays in the low and high pump power region.

Cd3(MoO4)(TeO3)2: A Polar 3D Compound Containing d10-d0 SCALP-Effect Cations.

The new polar 3D cadmium molybdotellurite Cd3(MoO4)(TeO3)2 was obtained by means of a high-temperature solid-state method. Cd3(MoO4)(TeO3)2 is a monoclinic crystal system, and it exhibits the polar space group P21 (No. 4). The structure of Cd3(MoO4)(TeO3)2 can be viewed as a complicated 3D architecture that is composed of distorted CdOn (n = 6, 7) polyhedra, TeO3 trigonal pyramids, and MoO4 polyhedra. The compound features the first 3D NCS cadmium molybdotellurite with 1D 4- and 6-MR channels and a polar structure originating from the TeO3 groups, MoO4 groups, and displacements of d10 Cd2+ cations. The results were further confirmed by calculations of the net polarization. The UV-vis spectrum and thermal properties indicate that Cd3(MoO4)(TeO3)2 exhibits a broad transparent region and excellent thermal stability. SHG tests of Cd3(MoO4)(TeO3)2 revealed that its response is approximately the same as that of KH2PO4 at the same grain size between 105 and 150 μm and that it is phase-matchable.

High-temperature Raman spectroscopy of the Cs2O–B2O3–MoO3 system for CsB3O5 crystal growth

Raman spectroscopy at high temperature has been applied to study in situ the microstructure of the solution in a Cs2O–B2O3–MoO3 growth system. A crystal–solution interface was observed. The BO groups consist of spiral chains based on B3O4Ø2 rings in the solution (Ø is a bridging O atom). The Raman spectrum of the solution indicates that MoO4 tetrahedra existed in the growth system. The nonbridging O atoms of the chains combined with the MoO4 groups, which decreased the viscosity. The Raman spectra near the interface show that at the boundary an isomerization reaction from three- to four-coordinated boron occurred. The formation of B3Ø7 triborate groups occurred. The morphology of the CsB3O5 crystal resulting from spontaneous crystallization was observed to correspond to our expectations.

Luminescent properties and energy transfer of Sm3+ doped Sr2CaMo1-xWxO6 as a potential phosphor for white LEDs

A series of Sm3+ doped Sr2CaMo1-xWxO6 phosphors were synthesized through solid state reaction process and their luminescent properties have been investigated. They presented excitation bands in UV, near UV and blue regions, originating from charge transfer transitions within Mo(W)O6 or Sm3+ f–f transitions. Concentration quenching still occurs among MoO6 groups even when Mo concentration is very low, however, if there is no Mo content in Sr2CaMo1-xWxO6 phosphors, absorption in near UV region cannot happen. It was found there is a big difference between the calculated optical band gap of Sr2CaMo0.02W0.98O6: 2% Sm3+ and that of Sr2CaMo0.01W0.99O6: 2% Sm3+. Band structure and density of state of Sr2CaMo0.5W0.5O6 were examined to explore the origination of charge transfer transition. Site occupation of Sm3+ in host lattice was discussed based on Raman spectra and group theory analysis. There are two kinds of luminescence centers in Sm3+ doped Sr2CaMo1-xWxO6 (x > 0) phosphors. When 98% Mo were substituted by W, the excitation band at 350 nm by monitoring 608 nm emission in Sr2CaMo0.02W0.98O6: 2%Sm3+ is about 8.5 times stronger than that in Sr2CaMoO6: 2%Sm3+. Energy transfer process was also discussed considering the overlap between the emission spectrum of Mo(W)O6 groups and the absorption spectrum of Sm3+, as well as the atom arrays of Mo6+(W6+), O2− and Sm3+.

Effect of Crystallite Size and Crystallinity on Photoluminescence Properties and Energy Transfer of Y6MoO12:Eu

The phosphors Y6MoO12:Eu3+ have been synthesized via citrate complexation method at different calcination temperatures. The evolutions of the crystal structure and the photoluminescence (PL) properties were characterized by means of powder X‐ray diffraction (XRD), Raman and PL spectra, respectively. It was revealed that a red emission could be obtained via three excitation channels, namely f–f transition of Eu3+ ions, charge‐transfer transition from O2 to Eu3+, and interband transition (IBT) of MoO6 groups. The PL spectra and their temporal decay character of Eu3+ ions depended on both crystal structure and excitation channel. The emission reduced with the crystallite size when Eu3+ ions were excited directly, but the emission evolved in a different model with the host lattices were excited. The effect of grain boundary and other lattice defect on the energy transfer and dissipation within the phosphors were discussed.

Synthesis, Crystal Structure, and Properties of the Sodium Molybdate Fluoride Na3MoO4F

AbstractThe compound Na3MoO4F was synthesized by high temperature solution methods. Single‐crystal X‐ray diffraction analysis reveals that Na3MoO4F crystallizes in the orthorhombic space group Pnma (No. 62) with lattice constants a = 5.588(2) Å, b = 7.515(3) Å, c = 12.876(5) Å, and Z = 4. The crystal structure consists of isolated MoO4 groups and [FNa3]∞ chains, which are connected by Na–O bonds to form a three‐dimensional framework. A detailed structure comparison between Na3MoO4F and NaMoO3F was carried out. IR spectroscopy and bond valence sum analysis of Na3MoO4F indicate that the structure is reasonable. In addition, the electronic structure was investigated by the first‐principles method.

Changes of birefringence and fine structure tensor in KSc(MoO4)2 induced by ferroelastic phase transitions

Phase transitions in KSc(MoO4)2 doped with Cr3+ are studied by the electron paramagnetic resonance and birefringence techniques in the temperature range covering the three ferroelastic phases. The study is aimed at showing in what way a morphic birefringence in the ferroelastic phases in KSc(MoO4)2 may relate to the deformation of the coordination surroundings of Sc3+ ion seen in this crystal via changes of the fine structure tensor D. Based on the motion of oxygen atoms of the MoO4 groups constituting the environment of Sc3+ions, a new model of the crystal structure deformation on transition from the ferroelastic phase II to the phase III is built. This model accounts for the morphic birefringence and changes in the orientation of the optical indicatrix axes in KSc(MoO4)2.

Gd3B(W,Mo)O9: Eu3+ red phosphor: From structure design to photoluminescence behavior and near-UV white-LEDs performance

The photoluminescence behavior of a high efficient red phosphor Gd3B(W,Mo)O9:Eu3+ designed according to crystal structure and electronic structure is presented in detail. The substitution of isolated WO6 group by MoO6 makes the absorption band edge extend from 360nm to 440nm, as designed to fit the excitation of near ultraviolet (NUV) LED chip, which could be interpreted by the density functional theory calculations. The extreme low symmetry (C1) of Eu3+(Gd3+) site enables Eu3+ ion to show dominant electronic dipole transition 5D0→7F2 (∼616nm) with five apparent splitting peaks according to group theory, which is almost 10 times stronger than that of commercial Y2O2S:Eu3+ upon ∼385nm excitation. The outstanding thermal stability of photoluminescence of this phosphor up to 523K may probably be owed to the energy transfer from isolated MoO6 groups to the well-dispersed Eu3+ ion separated by BO3 groups. The performance of NUV white-LEDs package fabricated with a blue, green and this red phosphor is also demonstrated. It shows high color stability of the white light (CIE coordinate (0.320, 0.349), CCT 6031K, at 20mA) under the DC drive current varied from 20mA to 350mA, verifying the potential application of the red phosphor in tri-color phosphors coated white-LEDs.

A narrow red-emitting phosphor of NaLa_4[Mo_3O_15]F:Eu^3+ with broad excitation band extending in blue wavelength region

Abstract: Eu3+-doped NaLa4Mo3O15F was prepared by solid-state method and characterized by X-ray powder diffraction (XRD) and scanning electron microscope (SEM). The luminescence properties such as the excitation and emission spectra, the internal quantum efficiency (QE) and the thermal stability were investigated. The optimal level of Eu3+-doping was determined by the luminescence intensities and QEs. The phosphor exhibits a bright red luminescence at 615 nm corresponding to the electric dipole transition 5D0→7F2, which is more efficient than the commercial phosphor of Y2O2S:Eu3+. With the increase of Eu3+-doping the charge transfer band (CTB) shows an obvious red-shift, which presents a longer wavelength than any other reported Eu3+-doped molydates with non-cubic structures. NaLa4Mo3O15F:Eu3+ has excellent properties such as the high quantum efficiency excited in near-UV and blue wavelength, the high thermal stability, etc. This is benefited from its structural characteristics: the cubic crystalline phase with MoO6 groups and the incorporation of F- ions in the host lattices.

How Strain Affects the Reactivity of Surface Metal Oxide Catalysts

Highly dispersed molybdenum oxide supported on mesoporous silica SBA-15 has been prepared by anion exchange resulting in a series of catalysts with changing Mo densities (0.2-2.5 Mo atoms nm(-2) ). X-ray absorption, UV/Vis, Raman, and IR spectroscopy indicate that doubly anchored tetrahedral dioxo MoO4 units are the major surface species at all loadings. Higher reducibility at loadings close to the monolayer measured by temperature-programmed reduction and a steep increase in the catalytic activity observed in metathesis of propene and oxidative dehydrogenation of propane at 8 % of Mo loading are attributed to frustration of Mo oxide surface species and lateral interactions. Based on DFT calculations, NEXAFS spectra at the O-K-edge at high Mo loadings are explained by distorted MoO4 complexes. Limited availability of anchor silanol groups at high loadings forces the MoO4 groups to form more strained configurations. The occurrence of strain is linked to the increase in reactivity.

Y2MoSe3O12 and Y2MoTe3O12: Solid-state synthesis, structure determination, and characterization of two new quaternary mixed metal oxides containing asymmetric coordination environment

Two new quaternary yttrium molybdenum selenium/tellurium oxides, Y2MoSe3O12 and Y2MoTe3O12 have been prepared by standard solid-state reactions using Y2O3, MoO3, and SeO2 (or TeO2) as reagents. Single-crystal X-ray diffraction was used to determine the crystal structures of the reported materials. Although both of the materials contain second-order Jahn–Teller (SOJT) distortive cations and are stoichiometrically similar, they reveal different structural features: while Y2MoSe3O12 shows a three-dimensional framework consisting of YO8, MoO6, and SeO3 groups, Y2MoTe3O12 exhibits a layered structure composed of YO8, MoO4, TeO3, and TeO4 polyhedra. With the Mo6+ cations in Y2MoSe3O12, a C3-type intraoctahedral distortion toward a face is observed, in which the direction of the out-of-center distortion for Mo6+ is away from the oxide ligand linked to a Se4+ cation. The Se4+ and Te4+ cations in both materials are in asymmetric coordination environment attributed to the lone pairs. Elemental analyses, infrared spectroscopy, thermal analyses, intraoctahedral distortions, and dipole moment calculations for the compounds are also presented.

Synthesis, crystal structure and photoluminescent properties of Eu3+ ion-activated R4MoO9 (R = Y, Gd, and Lu)

Rare earth molybdates R4MoO9 (R = Y, Gd, and Lu) with Eu3+ ion-doped were synthesized by solid-state reaction. The phase structure, optical absorption and photoluminescence properties of the as-prepared powder samples were studied. The powder X-ray diffraction patterns indicated that all the compounds crystallized in a hexagonal structure, and the lattice parameters reduced in the order of the ionic radii of R. The UV–visible diffuse reflectance spectra revealed that the compounds had a strong absorption of near-UV light due to the excitation of MoO6 groups in the host lattices. The energy absorbed by the host lattices could then be transferred to doped Eu3+ ions, resulting in red emission due to the f–f transitions of Eu3+ ions. The optical absorption and photoluminescence properties of the compounds indicated that they might be candidates as the color-conversion red phosphors for solid-state lighting.

Anomalous upconversion emission of Eu3+–Yb3+–MoO6 in double perovskites induced by a laser

The anomalous upconversion (UC) emission of Eu3+–Yb3+–MoO6 in Sr2Ca(Mo,W)O6 double perovskites is presented in detail and the proper theoretical interpretation is proposed. The relative intensity ratios of the magnetic dipole transition 5D0 → 7F1 at ∼594 nm to the electric dipole transition 5D0 → 7F2 at ∼615 nm of Eu3+ are changed for both A-site (Sr, C1 symmetry) and B-site (Ca, Ci symmetry) substitution by Eu3+ in Sr2Ca(Mo,W)O6 when comparing the UC emission spectra with the Stokes luminescence spectra, which may be due to the difference in energy transfer efficiency between Yb3+–Yb3+ to Eu3+ and (Mo,W)O6 to Eu3+. Another remarkable phenomenon is the emission peak at ∼700 nm, ascribed to the 5D0 → 7F4 transition, which is observed in the UC spectra for the samples with Mo while it is absent in the Stokes luminescence spectra. Furthermore, this peak almost disappears for those samples without Mo in the UC spectra. Theoretical analysis and Raman spectra are utilized to interpret these phenomena, which can probably be accounted for by the polarizability variation of MoO6 groups induced by a 976 nm laser beam.