La Lu Research Articles

Hydrothermal mineral replacement of bastnäsite by rhabdophane and monazite: effects of temperature on mineralogy, REE immobilisation, and fractionation

The rare-earth elements (REEs, La–Lu, Y) are essential for the development of renewable technologies. Bastnäsite (REECO3F) is a common REE ore mineral that is often subject to hydrothermal alteration at all crustal levels. Mechanisms of hydrothermal bastnäsite alteration therefore govern the evolution of REE deposits, though these mechanisms remain poorly understood. This experimental work investigates the hydrothermal replacement of bastnäsite by rhabdophane (REEPO4∙xH2O, x = 0–1) and monazite (REEPO4) in phosphatic fluids. Two temperature-dependent alteration pathways were identified; both follow the coupled dissolution-reprecipitation (CDR) mechanism. At 90 °C, bastnäsite was replaced by highly-porous metastable rhabdophane which was then replaced by monazite, forming an inner layer of rhabdophane and an outer layer of monazite. At 220 °C, bastnäsite was replaced directly by monazite. Although replacement initiated more quickly at 220 °C, greater overall replacement occurred at 90 °C (~ 61 wt.% after 500 h, compared to ~ 13 wt.% at 220 °C) due to surface passivation by monazite at 220 °C. Geochemical analyses showed REE fractionation during bastnäsite alteration. At 90 °C, rhabdophane was enriched in heavy REEs (Eu–Lu, Y), likely due to the evolving fluid chemistry, while at 220 °C secondary monazite was enriched in Sm and Ho compared to bastnäsite. These results indicate that: 1) the hydrothermal alteration of bastnäsite by rhabdophane and monazite in ore deposits leads to REE immobilisation, with little net loss of REEs to solution; 2) rhabdophane is metastable relative to monazite at 90 °C, and; 3) variable temperatures can cause different mineral textures and REE fractionation trends during hydrothermal alteration and mineral replacement.

Exploring high-performance environmental barrier coatings for rare earth silicates: A combined approach of first principles calculations and machine learning

RE2Si2O7 is promising materials for environmental barrier coating (EBC), but the vast phase space poses challenges for the screening of RE2Si2O7. It follows that a combined approach of first principles calculations and machine learning is proposed for this problem, with establishing a comprehensive database comprising β-, γ- and δ-RE2Si2O7 (RE=La–Lu, Y, Sc) and correlating their mechanical/thermal properties on structural characteristics. It is revealed the [O3Si–O–SiO3] structure and polyhedron distortion affect mechanical properties of RE2Si2O7, while criteria for selecting RE2Si2O7 with low thermal conductivity are identified, including complex crystal structures, chemical bond inhomogeneity, and strong non-harmonic lattice vibrations. Also, the machine learning model accurately predicts the coefficient of thermal expansion (CTE) and minimum thermal conductivity (λmin) of RE2Si2O7, with volume and mass variations identified as critical factors, respectively. This integrated approach efficiently screens RE2Si2O7 for EBC application and enables rapid assessments of their thermal properties.

SYNTHESIS OF SODIUM HETEROPOLY DECATUNGSTOEUROPATE(III) WITH PLATE-LIKE SURFACE MICROMORPHOLOGY

In order to develop an express procedure for the synthesis of the Eu(III)-containing heteropoly compound Na9[Eu(W5O18)2]·35H2O, a study of the interaction in an aqueous solution of the Na2WO4 – HNO3 – Eu(NO3)3 – H2O system acidified to an acidity of Z = ν(H+)/ν(WO42–) = 0.80 was carried. A procedure for obtaining a single-phase sample of Na9[Eu(W5O18)2]·35H2O is proposed, which is performed by a simple technique in a short time, which does not exceed 5 days from the addition of reactants to obtaining the target product with a yield of more than 90%. It was established that during salting out, the addition of an organic solvent (propan-2-one) results in the crystallization of Na9[Eu(W5O18)2]·35H2O normal salt with plate-like surface micromorphology. The set of oscillations characteristic for the heteropoly tungstate anion with the Peacock–Weakley type of structure, [Eu(W5O18)2]9–, was established by the methods of FT-IR spectroscopy and FT-Raman spectroscopy. By the method of FT-IR spectroscopy the absence of organic solvent molecules (propan-2-one) in the composition of the crystalline product was established. The revealed set of vibrations in the FT-IR and Raman spectra of the isolated salt (the most intense valence vibrations at 710, 797, 849, and 935 cm-1 in the FT-IR spectrum; intense bands in the region of 930–980 cm-1 in the Raman spectrum) is characteristic of the site group of the heteropoly anion [Ln(W5O18)2]9– (Ln = La–Lu) and is identical to the FT-IR and Raman spectra of salts, the crystal structure of which has been reliably established by single crystal X-ray diffraction analysis. By the method of scanning electron microscopy, it was shown that the grain size of Na9[Eu(W5O18)2]·35H2O powder is up to 500 nm. The single phase of the salt was confirmed by the uniform surface contrast in the backscattered electron imaging (BEI) mode and by the uniform distribution of Eu, Na, W, and O during the scanning of the surface in the characteristic X-ray radiation.

Regularity of thermal characteristics, thermoelectric properties of EuLnCuSe3 compounds (Ln = La–Lu)

Regularity of thermal characteristics, thermoelectric properties of EuLnCuSe3 compounds (Ln = La–Lu)

Discovering the ultralow thermal conductive A2B2O7-type high-entropy oxides through the hybrid knowledge-assisted data-driven machine learning

Lattice engineering and distortion have been considered one kind of effective strategies for discovering advanced materials. The instinct chemical flexibility of high-entropy oxides (HEOs) motivates/accelerates to tailor the target properties through phase transformations and lattice distortion. Here, a hybrid knowledge-assisted data-driven machine learning (ML) strategy is utilized to discover the A2B2O7-type HEOs with low thermal conductivity (κ) through 17 rare-earth (RE = Sc, Y, La–Lu) solutes optimized A-site. A designing routine integrating the ML and high throughput first principles has been proposed to predict the key physical parameter (KPPs) correlated to the targeted κ of advanced HEOs. Among the smart-designed 6188 (5RE0.2)2Zr2O7 HEOs, the best candidates are addressed and validated by the principles of severe lattice distortion and local phase transformation, which effectively reduce κ by the strong multi-phonon scattering and weak interatomic interactions. Particularly, (Sc0.2Y0.2La0.2Ce0.2Pr0.2)2Zr2O7 with predicted κ below 1.59 Wm−1 K−1 is selected to be verified, which matches well with the experimental κ = 1.69 Wm−1 K−1 at 300 K and could be further decreased to 0.14 Wm−1 K−1 at 1473 K. Moreover, the coupling effects of lattice vibrations and charges on heat transfer are revealed by the cross-validations of various models, indicating that the weak bonds with low electronegativity and few bonding charge density and the lattice distortion (r*) identified by cation radius ratio (rA/rB) should be the KPPs to decrease κ efficiently. This work supports an intelligent designing strategy with limited atomic and electronic KPPs to accelerate the development of advanced multi-component HEOs with properties/performance at multi-scales.

Thermodynamics of phase stability and disorder in Inter-Lanthanide ternary ABO3 oxides from first principles

Inter-lanthanide ternary oxides (IL-ABO3) find application in various technological fields due to their diverse properties and flexible chemistries that are readily synthesizable in multiple crystal structures. Here, we investigate the chemistry-dependent thermodynamic formability and the tendency to disorder for IL-ABO3 (A, B = La–Lu) compounds having different structures using density functional theory. We reproduce the previously observed relationship between the IL-ABO3 crystal structure and difference in the A and B ionic radii. We investigate the formation of metastable phases, finding a region of IL-ABO3 chemistries with rich metastability in a small energy interval. We analyze the influence of disordering on the stability of the ground state structures, correlating the propensity for disorder with the energy difference between different cation orderings. Our results provide fundamental insights into the phase stability of IL-ABO3, the energetics of their metastable structures, and their tendency to disorder, paving the way towards their broader technological applicability.

Adsorption of rare earth elements in carboxylated mesoporous carbon

The separation of Rare Earth Elements (REEs) from various non-conventional sources is critically important to maintain the supply–demand balance of REEs in the western world. In this research, we have investigated coal Fly Ash (CFA) as the non-conventional source of REEs. In order to recover REEs, we have synthesized carboxylate-functionalized mesoporous carbon (CMC) to harness the chelation-induced adsorption of REEs. These adsorbents were characterized with pore textural properties, FTIR spectroscopy, and SEM-EDX mapping. In the initial study with single-component La(III) Dy(III) and Lu(III), it was revealed that CMC can adsorb those REEs 2–4 times more than that of pristine mesoporous carbon confirming the effective role of the carboxylate group in the REE separation. Furthermore, the affiliation of the carboxylate group towards heavier REEs (Lu > Dy > La, when present is equal amounts) provides an added benefit of this adsorbent owing to the high demand for heavier REEs in the technology sectors. The leachate solution produced from CFA contained sixteen REEs in the range of 50–200 ppb for most of the REEs. It was revealed that CMC can extract 80–90% of all the REEs thereby further confirming the success of the CMC as an effective REE sorbent. Three successive cycles of adsorption and desorption of REEs with the same CMC revealed the consistent adsorption capacity of REEs. In-situ X-ray Absorption Near Edge Spectroscopy (XANES) analysis confirmed the + 3 oxidation states of La, Dy, and Lu within CMC. In-situ Extended X-ray Absorption Fine Structure (EXAFS) analysis revealed the shortening of mean La-O, Dy-O, and Lu-O bond distance by 0.03–0.05 Å thereby confirming the coordination of these REEs with carboxylate groups present on CMC.

On the Crystal Chemistry of RE2Si2O7: Revisited Structures, Group–Subgroup Relationship, and Insights of Ce3+-Activated Radioluminescence

Polymorphic rare-earth disilicates RE2Si2O7 (RE = La–Lu, Y, and Sc) are attractive materials as thermal barrier coatings and scintillators; however, the orthorhombic E(δ)-type (RE = Eu–Ho and Y) and the triclinic F-type (RE = Sm and Eu) remain structurally controversial hitherto. In this work, we revisit the crystal structures of E(δ)-RE2Si2O7 (Pnma), F-RE2Si2O7 (P1̅), and the monoclinic G-La2Si2O7 (P21/n) by X-ray single-crystal/powder diffraction. The second-harmonic generation (SHG) and/or the local-structure-sensitive VUV–UV–vis luminescence of Ce3+/Eu3+ validate the structure determination. E(δ)-RE2Si2O7 (RE = Eu–Ho) crystallizes in the centrosymmetric Pnma instead of the previous noncentrosymmetric Pna21 (a subgroup of Pnma). Increasing the RE3+ radius results in structural transformations of the reconstructive-type E(δ) ↔ F and translationengleiche subgroup–group relationship F ↔ G (RE = La–Nd). More importantly, we perform a complete survey of 17 structure-types over 63 compounds of RE2Si2O7 and their related transformations depending on the radius of RE3+. On the basis of these studies, one could (i) predict the potential polymorphs of RE2Si2O7, including the high-pressure phase and the RE2Si2O7 solid solutions; (ii) correlate the coefficient of thermal expansion (CTE) with the crystal structure, and (iii) understand the unusual radioluminescence of (Gd,La)2Si2O7:Ce3+ high-temperature scintillators.

Особенности синтетических подходов к получению станнатов со структурой пирохлора и изучение их термодинамических свойств

The paper discusses synthetic approaches to the preparation of compounds with a pyrochlore structure using the example of compounds of composition Ln2Sn2O7 (Ln = La–Lu). Optimal temperature-time schemes for synthesis of single-phase samples were established and crystallographic parameters of compounds were determined.Morphology of samples obtained at different conditions was determined. Heat capacity measured and calculated thermodynamic functions in a wide temperature range (2.5–1300 K).

Systematic Crystallization of NH4Ln(MoO4)2 as a Family of Layered Compounds (Ln = La-Lu and Y), Derivation of Ln2Mo4O15, Crystal Structure, and Photoluminescence.

NH4Ln(MoO4)2 (Ln = La-Lu lanthanide, Y) was crystallized via hydrothermal reaction as a new family of layered materials, from which phase-pure Ln2Mo4O15 was successfully derived via subsequent annealing at 700 °C for the series of Ln elements excluding Ce and Lu. Detailed structure analysis revealed that the ionic size of Ln3+ decisively determined the crystal structure and Mo/Ln coordination for the two families of compounds. NH4Ln(MoO4)2 was analyzed to be orthorhombic (Pbcn space group, no. 60) and monoclinic (P2/c, no. 13) for the larger and smaller Ln3+ of Ln = La-Gd and Ln = Tb-Lu (including Y), respectively, where both the crystal structures have a layered topology featured by the alternative stacking of a [Ln(MoO4)2]- three-tier infinite anionic layer and interlayer NH4+. Four types of crystal structures were found for the Ln2Mo4O15 series, which are monoclinic (P21/a, no. 14) for Ln = La, triclinic (P1̅, no. 2) for Ln = Pr-Sm, triclinic (P1̅, no. 2) for Ln = Eu and Gd, and monoclinic (P21/c, no. 14) for Ln = Tb-Yb (including Y). The photoluminescence of NH4Ln(MoO4)2 (Ln = Eu, Tb) and Ln2Mo4O15:Eu3+ (Ln = La, Gd, Y) was thoroughly investigated in terms of spectral features, quantum efficiency, fluorescence decay, and CIE chromaticity. The thermal stability of luminescence was also studied for Ln2Mo4O15:Eu3+, and the observed charge-transfer excitation components were successfully correlated with the features of the Mo-O polyhedron/unit.

Nucleation and growth of L12-Al3RE particles in aluminum alloys: A first-principles study

The internal mechanisms of nucleation and growth of L12-Al3RE (RE = Sc, Y, La–Lu) second phases in Al alloys were investigated by combining first-principles calculations with quasi-harmonic approximation (QHA). The calculated results show that the diffusion rate Ds and chemical potential ΔGV increase with the increase of temperature. With the increase of atomic number, the Ds and the strain energy ΔECS increase firstly from Sc to La, and then decreases, while the calculated interface energy γα/β and ΔGV show opposite tendency. Based on above calculated results, the critical nucleation radius R∗ and coarsening rate KLSW are obtained from the classical nucleation theory (CNT) and LSW model of the Ostwald ripening of particles, respectively. With the increase of atomic number, the R∗ increases firstly, and then decreases for all planes at finite temperatures. Whereas the KLSW shows opposite variation to the R∗. From this point of view, it is reasonably speculated that Y and later RE elements can replace the expensive Sc for heat-resistance Al alloys. The solubility c∞ of particles is usually very small at low temperature, and there is obvious solubility only when the temperature reaches 600 K. The surface energies Esur of Al3RE compounds and Al solid solution are respectively larger and smaller than that of pure Al, respectively, except for the surface (001) and (110) of Al3La. For all planes, with the increase of atomic number of RE, Esur decreases firstly from Sc to La, and then increases linearly to Lu. These results are helpful for designing high performance heat-resistance Al alloys.

Chemical stability of rare-earth elements’ uranyl arsenates with general formula MIII(AsUO6)3·16H2O (MIII–La–Lu) in aqueous solution

Chemical stability of rare-earth elements’ uranyl arsenates with general formula MIII(AsUO6)3·16H2O (MIII–La–Lu) in aqueous solution

Enrichment characteristics and sources of the critical metal yttrium in Zhijin rare earth-containing phosphorites, Guizhou Province, China

Yttrium (Y) is a critical metallic element that is used widely in modern scientific, technological, and industrial applications. Phosphorites in the Zhijin area of Guizhou Province, China, are famous for Y enrichment, but the enrichment characteristics and sources remain unclear. Previous studies suggested that the sources of rare earth elements (REEs, La–Lu) and Y (REYs, La–Lu+Y) were related to hydrothermal deposition. However, this study presents evidence refuting that hypothesis, with major and trace elemental data collected with quadrupole–inductively coupled plasma–mass spectrometry (Q–ICP–MS) analysis. These data show that Y in Zhijin REYs-containing phosphorites has a normal distribution and is particularly enriched relative to other REYs. The Y enrichment degree is different at different ∑REY intervals. Specifically, the Y enrichment degree is higher at lower ∑REY values and lower at higher ∑REY values. The REYs-containing phosphorites show features of primary phosphorites. Both REEs and Y have good correlations with P2O5 in the phosphorites with low REYs contents (total REYs < 535 ppm), whereas at high REYs contents (total REYs ≥ 535 ppm), REEs have a good correlation with P2O5 but Y does not. Inconsistent enrichment processes of REYs are suggestive of complex sources of Y. Thus, seafloor hydrothermal fluids were not the direct source of Y. Normal seawater mixed with terrestrial sources might have contributed to the origin of Y here. This study could lead to improvements in Y mineral resource explorations and the situation involving the global REYs supply crisis.

A new method for identifying the role of marital preferences at shaping marriage patterns

AbstractWe develop a method which assumes that marital preferences are characterized either by the scalar-valued measure proposed by Liu and Lu, or by the matrix-valued generalized Liu–Lu measure. The new method transforms an observed contingency table into a counterfactual table while preserving its (generalized) Liu–Lu value. After exploring some analytical properties of the new method, we illustrate its application by decomposing changes in the prevalence of homogamy in the US between 1980 and 2010. We perform this decomposition with two alternative transformation methods as well where both methods capture preferences differently from Liu and Lu. Finally, we use survey evidence to support our claim that out of the three considered methods, the new transformation method is the most suitable for identifying the role of marital preferences at shaping marriage patterns. These data are also in favor of measuring assortativity in preferences à la Liu and Lu.

KLn(MoO4)2 micro/nanocrystals (Ln = La-Lu, Y): systematic hydrothermal crystallization, structure, and the performance of doped Eu3+ for optical thermometry.

Systematic crystallization of KLn(MoO4)2 double molybdate micro/nanocrystals was achieved in this work for the family of lanthanide elements (excluding Pm) and Y via hydrothermal reaction under the optimized conditions of pH = 7, Mo/Ln molar ratio R = 5 and 200 °C, with which the intrinsic influence of lanthanide contraction on phase preference, crystallite morphology (size/shape) and crystal structure was clearly revealed. Extended synthesis also produced KLa1-xEux(MoO4)2 (KLM:xEu) and KY1-yEuy(MoO4)2 (KYM:yEu) red phosphors, and detailed spectral analysis found that the layered structure of orthorhombic KYM allows Eu3+ to have a high quenching content of ∼70 at% (y = 0.7) and higher quantum efficiency and thermal stability of luminescence. Application also indicated that the KYM:0.7Eu optimal phosphor has the potential for optical temperature sensing with the thermally coupled 5D0 and 5D1 energy levels of Eu3+.

Tolerance Factor for Huntite-Family Compounds

85 RM3(BO3)4 (R is the rare-earth element (Y, La–Lu) and M = Al, Sc, Cr, Fe, or Ga) compounds with the huntite structure have been analyzed. The analysis of the structures has made it possible to determine critical atomic displacements during the phase transition R32 ↔ P3121 and establish how these critical displacements can be controlled by varying the ionic radii. A tolerance factor has been derived and its threshold value below which the structure is stable in the R32 phase and above it, in the distorted P3121 phase, has been found. The formula has been tested on more than 30 huntite-family compounds and good agreement has been obtained. Therefore, it can be used with confidence to predict new compounds. At the moment, the tolerance factor has allowed us to establish previously unknown regularities in huntites.

Averaged Scale in Electronegativity Joined to Physicochemical Perturbations. Consequences of Periodicity.

In this work, we propose a new representative electronegativity scale χDC based on a statistical analysis of 11 electronegativity scales associated with electric ionic resonance energy, ionization potential, electron affinity, polarizability, electric force, average orbital energy, chemical potential, electrochemical reduction potential, and electric potential energy. Among these scales, it is the new PE° electronegativity scale, which relates the reduction potential E° to Pauling’s electronegativity scale. The scale χDC gives more weight to the physicochemical factors, which influence the electronegativity, but this scale is not necessarily the best electronegativity scale for the element. This scale is based on (1) the average of the experimental electronegativity values; (2) the proximity of an experimental value to the average given by the difference and the ratio to this average; (3) in critical cases, the periodicity network of the periods and the groups; and (4) the periodicity of the sequence of the ratios of the experimental electronegativity values to the best-selected electronegativity value. We have also taken as probe scales Nagle’s, Allred and Rochow’s, Allen’s (Hoffman’s and Politzer’s), PE°, Gordy’s, and Ghosh’s electronegativity scales in order to investigate the trend of the physicochemical factors which influence the electronegativity. With this trend, we have determined zones where a physicochemical property influences the electronegativity more. We have also found that physicochemical perturbations such as the orbital overlap, the stable configurations, the nephelauxetic effect, the width of the band gap, the ligand field stabilization energy, the penetration of the orbitals, and the lattice energy influence the electronegativity. Besides, we have analyzed the exactness of the electronegativity of the scales through the periodical ranking, the chemical tripartite separation among ionic, covalent, or metallic bond (taking into account the amplitude of the metalloid band), and the physicochemical property of bond force. The representative χDC electronegativity scale is the best in periodicity, followed by Batsanov’s and Pauling’s scales. In the type of chemical bond, the ranking depends on the number and kind of compounds in the sample, but in general, Pauling’s, the ARS, and Batsanov’s electronegativity scales are the best with a confidence interval of 95%. On the other hand, in the physical bond force, Batsanov’s, Pauling’s, Mulliken’s, Nagle’s, Allen’s, the ARS, and the χDC electronegativity scales are the best scales. Also, we have considered the free atom and the in situ hypotheses of electronegativity and used the low and high oxidation states to verify these hypotheses. Besides, as an example of the utility of this ranking of scales, we have analyzed the relation of lanthanum La and lutetium Lu to Group 3, lanthanides, and hafnium Hf. We also analyze the vertical, horizontal, Knight’s move, and isodiagonal periodicity of the electronegativity and associate this periodicity to a similar chemical–physical behavior of elements or ions.

Lanthanide Contraction in Action: Structural Variations in 13 Lanthanide(III) Thiophene-2,5-dicarboxylate Coordination Polymers (Ln = La–Lu, Except Pm and Tm) Featuring Magnetocaloric Effect, Slow Magnetic Relaxation, and Luminescence-Lifetime-based Thermometry

Thirteen new three-dimensional lanthanide(III)-2,5-thiophenedicarboxylate coordination polymers (Ln-CPs) with general formulas of [Ln2(2,5-TDA)3(DMA)2(H2O)]n (Ln-CPs 1–4) and [Ln2(2,5-TDA)3(DMA)2]n...

Library of UV-Visible Absorption Spectra of Rare Earth Orthophosphates, LnPO4 (Ln = La-Lu, except Pm)

In recent times, rare earth orthophosphates ( L n PO 4 ) have shown great potential as efficient optical materials. They possess either m o n a z i t e or x e n o t i m e –type structures. These light or heavy rare earth bearing orthophosphates also exhibit an extraordinary stability over geological time scale in nature, ∼10 9 years. In the present contribution, we measure, collect, and present a library of absorption spectra of all the L n PO 4 hosts ( L n = La–Lu, except Pm) using their single crystal samples, to conclude that the observed spectral features for wavelengths longer than 200 nm were attributable to either Ln- or defect related centers, which corroborate the fact that they have a bandgap higher than 8.0 eV. The absorption band around wavelength, 275 nm, corresponds to defect absorption related to PO 3 centers and/or oxygen vacancies. The hosts can potentially be used to study and interpret unperturbed rare earth emissions due to absence of host related absorption above 300 nm. The information presented herein is expected to serve as a library of absorption spectra for geologists, physicists, material scientists, and chemists working in the field of rare earths.

Generalized synthesis of NaLn(MoO4)2 nano/microcrystals (Ln = La–Lu and Y): The effects of lanthanide contraction, structure, and down-/up-conversion luminescence

Systematic synthesis of scheelite-type double molybdate nano-/microcrystals NaLn (MoO4)2 (Ln = La–Lu lanthanides and Y) was successfully carried out via hydrothermal reaction at 180 °C without using any organic additive, and the intrinsic effects of lanthanide contraction on phase preference and crystallite morphology were unambiguously observed. It was shown that the products of larger Ln3+ (Ln = La–Dy) and smaller Ln3+ (Ln = Ho–Lu and Y) elements crystallized as tetragonal NaLn (MoO4)2 and new orthorhombic NaLnMo2O8·2H2O structures, respectively, with the latter being able to dehydrate to tetragonal NaLn (MoO4)2 upon calcination at ∼300 °C. Y was found to be a demarcation point for the two structures, and phase preference was shown to be influenced by solution pH and MoO42−/Y3+ molar ratio. With Eu3+ as a downconversion (DC) luminescence probe, the effects of Ln type (Ln = La, Gd, Y and Lu) and crystal structure were manifested. Furthermore, the upconversion (UC) luminescence of Yb3+/Ho3+ and Yb3+/Er3+ pairs in NaLu(MoO4)2 was studied for the first time, and strong red and green UC emissions were observed under the 978 nm laser excitation. Besides, the processes/mechanisms of UC were studied via varying the excitation power and were discussed with Yb3+-MoO42- dimer sensitizer.