Synthesis and thermal expansion behaviors of spin-coated Sc2Mo3O12 thin films

Orthorhombic Sc₂Mo₃O₁₂ films have been successfully prepared via spin coating technique followed by annealing at 500–750 °C. The phase composition, microstructure, morphology and negative thermal behavior of the synthesized Sc₂Mo₃O₁₂ films were investigated. XRD and XPS analysis indicate that as-deposited film is amorphous. Orthorhombic Sc₂Mo₃O₁₂ films can be prepared after post-annealing at 500–750 °C for 1 h. The crystallinity of Sc₂Mo₃O₁₂ films gradually improved with the increase of post-annealing temperature. SEM analysis shows as-deposited film is smooth and compact, and the grain size of Sc₂Mo₃O₁₂ film grows up as the post-annealing temperature increases. Variable temperature XRD analysis demonstrates that the synthesized orthorhombic Sc₂Mo₃O₁₂ films show stable thermo-chemical and anisotropic NTE property in 25–700 °C. The corresponding coefficients of thermal expansion (CTEs) of the orthorhombic Sc₂Mo₃O₁₂ film in a, b and c directions are ?6.68 × 10^?6 °C^?1, 5.08 × 10^?6 °C^?1 and ?4.76 × 10^?6 °C^?1, respectively. The whole unit cell of the orthorhombic Sc₂Mo₃O₁₂ film shrinks and the volumetric CTE of the Sc₂Mo₃O₁₂ thin film is ?6.36 × 10^?6 °C^?1, and the linear CTE is about ?2.12 × 10^?6 °C^?1 (α_v = 3α_l).     

Preparation of In0.5Sc1.5Mo3O12 nanofibers and its negative thermal expansion property

Orthorhombic In_0.5Sc_1.5Mo₃O₁₂ nanofibers were prepared by electrospinning followed by a heat treatment. The effects of post-annealing temperatures on the phase composition, microstructure and morphology were investigated by XRD, SEM, HRTEM and XPS. Negative thermal expansion (NTE) behaviors of the In_0.5Sc_1.5Mo₃O₁₂ nanofibers were analyzed by high-temperature XRD. Results indicate that the as-prepared In_0.5Sc_1.5Mo₃O₁₂ nanofibers show an amorphous structure with smooth and homogeneous shape. The average diameter of the as-prepared In_0.5Sc_1.5Mo₃O₁₂ nanofibers is around 515 nm. Well crystallized orthorhombic In_0.5Sc_1.5Mo₃O₁₂ nanofibers could be prepared after post-annealing at 550 °C for 2 h with an average diameter of about 192 nm. The crystallinity of In_0.5Sc_1.5Mo₃O₁₂ nanofibers gradually improved with the increase of annealing temperature. However, too high post-annealing temperature leads to a damage of sample's fiber structure. The high-temperature XRD results reveal that In_0.5Sc_1.5Mo₃O₁₂ nanofibers show an anisotropic NTE, and the coefficients of thermal expansion (CTEs) along a-axis and c-axis were −5.95 × 10⁻⁶ °C⁻¹ and -3.54 × 10⁻⁶ °C⁻¹, while the one along b-axis is 5.61 × 10⁻⁶ °C⁻¹. The volumetric CTE of In_0.5Sc_1.5Mo₃O₁₂ nanofibers is −3.90 × 10⁻⁶ °C⁻¹ and the linear one is 1.3 × 10⁻⁶ °C⁻¹ in 25–700 °C.     

Tuning the phase transition temperature of Cr2(MoO4)3 by A-site substitution of scandium

A series of Cr_2-xSc_x(MoO₄)₃ solid solutions with tunable monoclinic-to-orthorhombic phase transition temperature have been synthesized via solid-state reaction. X-ray diffraction (XRD), transmission electron microscopy (TEM) and X-ray photoelectron spectroscopy (XPS) results show that all synthesized Cr_2-xSc_x(MoO₄)₃ (0?< x?≤?1.4) solid solutions are single phased with no impurities identified, which reveals that Cr³⁺ has been substituted by Sc³⁺ in Cr₂(MoO₄)₃. Monoclinic to orthorhombic phase transition temperature of Cr_2-xSc_x(MoO₄)₃ can be effectively tuned from 372?°C to room temperature as the substituted Sc³⁺-content (x) varies from 0 to 1.4. The synthesized Cr_0.6Sc_1.4(MoO₄)₃ crystalizes in an orthorhombic structure at room temperature, exhibiting anisotropic negative thermal expansion throughout the testing temperature range. The coefficient of thermal expansion measured by thermal mechanical analyzer (TMA) for Cr_0.6Sc_1.4(MoO₄)₃ is ?11.17?×?10^?6 °C^?1 in the testing temperature range of 30–600?°C. Moreover, the crystallization, micromorphology, density and coefficient of thermal expansion of Cr_0.6Sc_1.4(MoO₄)₃ are obviously sensitive to the twice sintering temperature, whereas none of such sensitivity is found for the phase transition temperature.     

Phase transition and negative thermal expansion properties in isovalently substituted In2−xScx(MoO4)3 ceramics

Sc-substituted In_2−xSc_x(MoO₄)₃ (0 ≤ x ≤ 2) ceramics were successfully synthesized by the solid state reaction method with the goal of tuning the phase transition temperature. Effects of Sc³⁺ substitution on the phase composition, microstructure, phase transition temperature and thermal expansion behavior of the In_2−xSc_x(MoO₄)₃ (0 ≤ x ≤ 2) ceramics were investigated using XRD, FESEM, EDX, XPS and TMA, respectively. The results indicate that all samples are single phase. The relative densities of the In_2−xSc_x(MoO₄)₃ ceramics increased gradually with increasing Sc³⁺ content. Investigations on thermal expansion properties of the In_2−xSc_x(MoO₄)₃ ceramics reveal that the temperature-induced phase transition from monoclinic to orthorhombic symmetry is strongly correlated to the Sc³⁺ content. The obtained In₂(MoO₄)₃ ceramics undergoes a structural phase transition from monoclinic to orthorhombic around 355.3 °C. The phase transition temperature can be significantly shifted from 355.3 °C (x = 0) to 31.9 °C (x = 1.5) by partially replacing In³⁺ cations with less electronegative Sc³⁺ cations. All In_2−xSc_x(MoO₄)₃ (0 ≤ x ≤ 2) ceramics exhibit strong negative thermal expansion above the phase transition temperature. In_0.5Sc_1.5(MoO₄)₃ exhibits linear NTE over the 100–700 °C temperature range with a linear coefficient of thermal expansion of −3.99 × 10⁻⁶ °C ⁻¹.     

Improving room temperature negative thermal expansion performance of Fe2-xScx(MoO4)3

Negative thermal expansion (NTE) performance of Fe₂(MoO₄)₃ is only found in a high-temperature range due to its monoclinic-to-orthorhombic (M-O) phase transformation temperature (PTT) at 503.5°C. To stabilize the orthorhombic phase of Fe₂(MoO₄)₃ at room temperature, a series of Fe_2-xSc_x(MoO₄)₃ (0≤x≤1.5) (abbreviated as F_2-xS_xM) were fabricated via solid-state reaction. Results indicate that the M-O PTT of Fe₂(MoO₄)₃ is successfully reduced from 503.5°C to 34.5°C by A-site cation substitution of Sc³⁺. The regulation mechanism is considered to be the decrease in electronegativity of (Fe_2-xSc_x)⁶⁺ in F_2-xS_xM. Both variable temperature X-ray diffraction (XRD) and thermal mechanical analysis (TMA) analysis results indicate that F_0.5S_1.5 M exhibits anisotropic NTE in 100–700°C. The results indicate that it can effectively improve the densification of Sc-substituted F_0.5S_1.5 M ceramics by two-step calcination process. Furthermore, higher second-step calcination temperature is beneficial for the formation of single-phased orthorhombic F_0.5S_1.5 M. The NTE response temperature range of F_0.5S_1.5 M ceramics second-step sintered at 1000°C is broadened to 30–600°C, and the corresponding coefficient of thermal expansion is -5.74 × 10⁻⁶°C⁻¹. The ease in the proposed design and preparation method makes NTE F_0.5S_1.5 M potential for a wide range of applications in precision mechanical, electronic, optical, and communication instruments.     

Negative thermal expansion coefficient of Sc-doped indium tungstate ceramics synthesized by co-precipitation

Co-precipitation was successfully applied to synthesize the Sc³⁺ doped In_2-xSc_x (WO₄)₃ (x = 0, 0.3, 0.6, 0.9 and 1.2) compounds. The composition- and temperature-induced structural phase transition and thermal expansion behaviors of Sc³⁺ doped In₂(WO₄)₃ were investigated. Results indicate that In_2-xSc_x (WO₄)₃ crystalizes in a monoclinic structure at 300 °C for x ≤ 0.3 and changes into hexagonal structure for x ≥ 0.6. Hexagonal In_1.1Sc_0.9(WO₄)₃ displays negative thermal expansion (NTE) with an average linear coefficient of thermal expansion (CTE) of −1.85 × 10⁻⁶ °C ⁻¹. After sintering at 700 °C and above, a phase transition from hexagonal to orthorhombic phase was observed in In_2-xSc_x (WO₄)₃ (x ≥ 0.6). Sc³⁺ doping successfully reduce the temperature-induced phase transition temperature of In_2-xSc_x (WO₄)₃ ceramics from 250 °C (x = 0) to room temperature (x = 0.9). When x = 0.9 and 1.2, the average linear CTEs of In_2-xSc_x (WO₄)₃ ceramics are −5.45 × 10⁻⁶ °C⁻¹ and -4.43 × 10⁻⁶ °C⁻¹ in a wider temperature range of 25–700 °C, respectively.     

New La3+ doped TiO2 nanofibers for photocatalytic degradation of organic pollutants: Effects of thermal treatment and doping loadings

The pure TiO₂ and lanthanum (La³⁺)-doped titanium dioxide (TiO₂) nanofibers were synthesized by electrospinning method followed via calcination at different temperatures (from 400 °C to 700 °C). Structures of the nanofibers were characterized by X-ray diffraction, scanning electron microscopy, TEM images and diffuse reflectance spectroscopy. The size of the nanofiber diameters was determined to be 129 and 101 nm, for pure TiO₂ and (0.1%)La³⁺:TiO₂ materials, respectively. The prepared nanofibers possess a crystalline structure, and wide distribution of the band-gaps, in the 2.867–3.210 eV range. Effects of La³⁺-dopant content, calcination temperature, and different doses of photocatalysts on the photodegradation efficiency were studied. The optimal level of La³⁺ and the optimal temperature of calcination were 0.1% La³⁺ and 600 °C, respectively. The photocatalytic degradation of methylene blue (91%, with a rate constant of 2.179 × 10^?2 min^?1) and ciprofloxacin (CIP) (99.5%, with a rate constant of 1.981 × 10^?2 min^?1) pollutants was highest on the (0.1%)La³⁺:TiO₂ annealed at 600 °C, after 300 min irradiation under visible light. This photocatalyst displayed sustainable efficiency for CIP degradation up to five consecutive uses.     

Microwave dielectric properties and thermal conductivities of low-temperature sintered (Na1-xKx)2MoO4 (x ≤ 0.2) ceramics

The Mo-based glass-free spinel-type structure of the (Na_1-xK_x)₂MoO₄ (x = 0.0, 0.1, and 0.2) ceramic series was prepared using the traditional solid-state method at the low sintering temperature (<650 °C). The microwave dielectric properties of the (Na_1-xK_x)₂MoO₄ series were determined in terms of phase compositions, crystal structure (via XRD), and microstructure analysis (via FE-SEM and EDS). The results revealed that the double-phase (cubic and orthorhombic) formation plays a significant role in the entire (Na_1-xK_x)₂MoO₄ series. It exhibits excellent dielectric properties: dielectric constant ε_r = 4 (1 GHz)/3.77 (15 GHz), tangent loss tan δ = 8.3 × 10^?2 (1 GHz)/7 × 10^?3 (15 GHz; Q × f = 2143 GHz), temperature coefficient of frequency (TCF) τ_f = ?6.45 ppm/°C, and room temperature thermal conductivity (κ) = 1.76 W/(m.K) for x = 0.1 at a sintering temperature of 575 °C. These make the (Na_1-xK_x)₂MoO₄ ceramic series a potential candidate for low-temperature co-fired ceramic (LTCC) substrate applications (as used in antennas) for high-speed data communications.     

Low-loss and ultra-low temperature sintering microwave dielectrics of pure and Ag-modified K2Mg2(MoO4)3 ceramics

Novel K_2–2xAg_2xMg₂(MoO₄)₃ (x = 0–0.09) ceramics were synthesized by conventional solid-state sintering method. Based on the X-ray diffraction (XRD) patterns, all samples were identified to belong to an orthorhombic structure with a space group of P212121(19). The pure phase K₂Mg₂(MoO₄)₃ specimen when sintered at 590 °C revealed the favorable microwave dielectric properties: ε_r of 6.91, Q×f of 21,900 GHz and τ_f of ?164 ppm/°C. The substitution of Ag⁺ for K⁺ in K_2–2xAg_2xMg₂(MoO₄)₃ (x = 0.01–0.09) ceramics led to the more stable structure and dramatically enhanced the Q×f to a value of 54,900 GHz at 500 °C. The microwave dielectric properties were related to the relative density, microstructure, ionic polarization, lattice energy, packing fraction, and bond valence of the ceramics. It was suggested that for ultra-low temperature co-fired ceramic (ULTCC) applications, K_1.86Ag_0.14Mg₂(MoO₄)₃ ceramic could be sintered at 500 °C, which revealed an excellent combination of microwave dielectric properties (ε_r =7.34, Q×f =54,900 GHz and τ_f =–156 ppm/°C) and good chemical compatibility with aluminum electrodes.     

Flower-like Sc2Mo3O12 nanosheet clusters: Synthesis,thermal expansion and photocatalytic properties

In this work, Sc₂Mo₃O₁₂ has been synthesized via one-pot hydrothermal reaction. The effects of process conditions on the crystal structure, morphology, photocatalytic activity and negative thermal expansion (NTE) behaviors of flower-like Sc₂Mo₃O₁₂ were systematically investigated. Results indicate that orthorhombic flower-like Sc₂Mo₃O₁₂ assembled by nano-size flaky crystal grains can be synthesized by one-pot hydrothermal reaction at a temperature as low as 120 °C for 2 h. The hydrothermal reaction temperature and time have no obvious effects on the crystal structure and morphology. However, the photocatalytic property of synthesized Sc₂Mo₃O₁₂ is sensitive to the above parameters. The sample synthesized at 200 °C for 2 h shows the best photocatalytic degradation of methyl orange, and the degradation rate is 73.32% in 2 h ¹The coefficient of thermal expansion (CTE) of Sc₂Mo₃O₁₂ is ?1.99 × 10^?6 °C^?1 in 50–500 °C tested using TMA. The high-temperature XRD analysis reveals that Sc₂Mo₃O₁₂ exhibits anisotropic NTE and the intrinsic CTE is measured to be ?2.09 × 10^?6 °C^?1 in 25–800 °C.     

Bond characteristics,sintering behavior and microwave dielectric properties of Ce2[Zr1−x(Ca1/3Sb2/3)x]3(MoO4)9 ceramics

Ce₂[Zr_1?x(Ca_1/3Sb_2/3)_x]₃(MoO₄)₉ (CZ_1?x(CS)_xM) (x = 0.02–0.10) ceramics were prepared by the conventional solid-state reaction method. The correlations between the chemical bond parameters and microwave dielectric properties were calculated and analyzed by using the Phillips–Van Vechten–Levine (P–V–L) theory. Phase composition and microstructures were evaluated by scanning electron microscopy and X-ray diffraction patterns. Lattice parameters were obtained by Rietveld refinements based on XRD data. Excellent properties for Ce₂[Zr_0.96(Ca_1/3Sb_2/3)_0.04]₃(MoO₄)₉ ceramic sintered at 775 °C: ε_r = 10.68, Q×f = 85,336 GHz and τ_f = ?7.58 ppm/°C were achieved.     

Effect of MgO and PVA on the Synthesis and Properties of Negative Thermal Expansion Ceramics of Zr2(WO4)(PO4)2

A green synthesis of Zr₂(WO₄)(PO₄)₂ ceramics from ZrO₂, WO₃ and P₂O₅ is presented. It is shown that the ceramics can be synthesized by one‐step sintering within 60 min. The relative density of the ceramics can be enhanced from about 75% without sintering additives to 99.8% of the theoretical value with 1.0 wt% MgO and 2.0 wt% polyvinyl alcohol. The grain sizes of the ceramics are smaller and more uniform with MgO added in the raw materials than with MgO added in the Zr₂(WO₄)(PO₄)₂ powder. The coefficients of thermal expansion are about ?2.325 × 10^?6, ?1.406 × 10^?6, ?1.509 × 10^?6 and ?1.384 × 10^?6°C^?1 for the samples without MgO, with MgO added in the raw materials, with MgO added in the Zr₂(WO₄)(PO₄)₂ powder and with MgO and PVA added in the raw materials, respectively.     

Thermal and magnetic properties of new scheelite type Cd1−3x□xGd2xMoO4 ceramic materials

The limited scheelite type Cd_1−3x□_xGd_2xMoO₄ solid solution, where 0 < x ≤ 0.25 and □ are cationic vacancies have been successfully synthesized by high-temperature annealing of CdMoO₄/Gd₂(MoO₄)₃ mixtures composed of 50.00 mol.% and less of Gd₂(MoO₄)₃. The obtained materials as well as CdMoO₄ and Gd₂(MoO₄)₃ were characterized by powder XRD, DTA–TG, DSC, and SEM techniques. A phase diagram of the pseudobinary CdMoO₄–Gd₂(MoO₄)₃ system was constructed. The eutectic point corresponds to 1350 ± 5 K and ∼70.00 mol.% of Gd₂(MoO₄)₃ in an initial CdMoO₄/Gd₂(MoO₄)₃ mixture. With decreasing of Gd³⁺ amount in the crystal lattice of CdMoO₄, a melting point of the Cd_1−3x□_xGd_2xMoO₄ solid solution increases from 1351 (x = 0.25) to 1408 K (x = 0). EPR method was used to identify the paramagnetic Gd³⁺centers in Cd_1−3x□_xGd_2xMoO₄ for different values of x parameter as well as to select biphasic samples containing both Cd_0.2500□_0.2500Gd_0.5000MoO₄ and Gd₂(MoO₄)₃.     

Investigation of the Ga-Sb-S chalcogenide glass with low thermo-optic coefficient as an acousto-optic material

In this study, two series of Ga_xSb_40-xS₆₀ (x = 4, 6, 8, 10 mol%) and Ga_ySb₃₆S_64-y (y = 3, 5, 6 mol%) glasses were prepared and the relationship between their compositional and acousto-optic (AO) properties was investigated systematically for the first time. In the Ga_ySb₃₆S_64-y system, the AO figure of merit (M₂) increased as the Ga increased, and the maximum M₂ of the Ga₆Sb₃₆S₅₈ glass was 455.78 × 10^?18 s³/g, which is ～301 times greater than that of fused silica and ～2.5 times greater than that of As₂S₃ chalcogenide (ChG) glass at 1550 nm. However, its thermo-optic coefficients (dn/dT) varied greatly (32.1 × 10^?6 °C^?1–57.2 × 10^?6 °C^?1), and acoustic attenuations (α) at 10 MHz were high, from 5.446 dB/cm to 7.274 dB/cm. In the Ga_xSb_40-xS₆₀ glass system, the M₂ value and α at different ultrasonic frequencies gradually decreased with the improvement of Ga. Compared with the Ga_ySb₃₆S_64-y system, the Ga_xSb_40-xS₆₀ glass system had lower α (at 10 MHz) and dn/dT, which are 5.001 dB/cm–5.563 dB/cm and 17.3 × 10^?6 °C^?1–55.6 × 10^?6 °C^?1, respectively. These results provide a significant reference for the further development of novel ChG glasses and help expand their application fields.     

Crystal structure,infrared-reflectivity spectra,and microwave dielectric properties of novel Ce2(MoO4)2(Mo2O7) ceramics

Novel Ce₂(MoO₄)₂(Mo₂O₇) (CMO) ceramics were prepared by a conventional solid-state method, and the microwave dielectric properties were investigated. X-ray diffraction results illustrated that pure Ce₂(MoO₄)₂(Mo₂O₇) structure formed upon sintering at 600 °C-725 °C. [CeO₇], [CeO₈], [MoO₄], and [MoO₆] polyhedra were connected to form a three-dimensional structure of CMO ceramics. Analysis based on chemical bond theory indicated that the Mo–O bond critically affected the ceramics’ performance. Furthermore, infrared-reflectivity spectra analysis revealed that the primary polarisation contribution was from ionic polarisation. Notably, the optimum microwave dielectric properties of ε_r = 10.69, Q·f = 49,440 GHz (@ 9.29 GHz), and τ_f = −30.4 ppm/°C were obtained in CMO ceramics sintered at 700 °C.     

High-entropy rare-earth disilicate (Lu0.2Yb0.2Er0.2Tm0.2Sc0.2)2Si2O7: A potential environmental barrier coating material

A new high-entropy ceramic (Lu_0.2Yb_0.2Er_0.2Tm_0.2Sc_0.2)₂Si₂O₇ ((5RE_0.2)₂Si₂O₇) was proposed as a potential environmental barrier coating (EBC) material for ceramics matrix composites in this work. Experimental results showed that the (5RE_0.2)₂Si₂O₇ synthesized by solid-phase sintering was a monoclinic solid solution and had good phase stability proved by no obvious absorption/exothermic peak in the DSC curve from room temperature to 1400 °C. It performed a lower coefficient of thermal expansion (2.08 ×10^?6-4.03 ×10^?6 °C^?1) and thermal conductivity (1.76–2.99 W?m^?1?°C^?1) compared with the five single principal RE₂Si₂O₇. In water vapor corrosion tests, (5RE_0.2)₂Si₂O₇ also exhibited better water vapor corrosion resistance attributed to the multiple doping effects. The weight loss was only 3.1831 × 10^?5 g?cm^?2 after 200 h corrosion at 1500 °C, which was lower than that of each single principal RE₂Si₂O₇. Therefore, (5RE_0.2)₂Si₂O₇ could be regarded as a remarkable candidate for EBCs.     

Sc- and W-substitution and tuning of phase transition in the Al2Mo3O12

Al₂Mo₃O₁₂ is a typical negative thermal expansion (NTE) material, whose thermal expansion behavior depends on its crystal phase. The thermal shock caused by temperature-induced phase transition limits its wide application. The two series of Al_{2. x}Sc_xMo₃O₁₂ (0 ≤ x ≤ 1) and Al₂Mo_3-xW_xO₁₂ (0 ≤ x ≤ 2.5) solid solutions with controllable phase transition temperature were synthesized via single cation substitution at the A or B position. The problem of thermal shock caused by the change of temperature is effectively solved in the synthesized Al_1.6Sc_0.4Mo₃O₁₂ and Al₂Mo_0.5W_2.5O₁₂, showing stable NTE performance above room temperature, and the coefficients of thermal expansion of which are ?2.19 × 10^?6 °C^?1 in 100–550 °C and ?4.25 × 10^?6 °C^?1 in 85–500 °C, respectively. A-site cation substitution is a more effective way to tune the thermal expansion properties of Al₂Mo₃O₁₂, which is attributed to the fact that the bond strength of A-O is weaker than that of B–O in the compound.     

Synthesis and characterization of fibrous La0.8Sr0.2Fe1-xCuxO3-δ cathode for intermediate-temperature solid oxide fuel cells

Aiming to offer a high-performance Co-free cathode for intermediate-temperature solid oxide fuel cells (IT-SOFCs), a series of La_0.8Sr_0.2Fe_1-xCu_xO_3-δ (LSFCux, x = 0.0–0.3) nanofiber cathodes were synthesized by the electrospinning method. The effects of various Cu doping amounts on the crystal structure, fiber morphology, and electrochemical performance of LSF nanofiber cathode materials were investigated. The results indicate that after being calcined at 800 °C for 2 h, the perovskite structure samples with a high degree of crystallinity are obtained. The morphology of electrospun nanofibers is continuous, and the average diameter of nanofibers is about 110 nm. In addition, the La_0.8Sr_0.2Fe_0.8Cu_0.2O_3-δ (LSFCu2) fiber cathode displays the optimal electrochemical performance, and the polarization resistance (R_p) is 0.674 Ω cm² at 650 °C. The doping of Cu transforms the main control step of the low-frequency band from dissociation of oxygen molecules to charge transfer on the electrode, and the maximum power density (P_m) of the Ni-SDC/SDC/LSFCu2 single cell reaches 362 mW cm^-2 at 650 °C.     

Syntheses and structures of the first two tetra-scandium substituted polyoxometalates

The first two tetra-Sc-substituted polyoxotungstates H₂K₂Na₂[Sc₄(H₂O)₁₀(B-β-SbW₉O₃₃)₂]·21H₂O (1) and H₂₀K₂Na₆[Sc₄(C₂O₄)₄(B-β-SbW₉O₃₃)₂][Sc₄(H₂O)₂(C₂O₄)₄(B-β-SbW₉O₃₃)₂]·64H₂O (2) have been synthesized and characterized by IR spectroscopy, AC impedance measurements, TG, PXRD, and single-crystal X-ray diffractions. Compound 1 represents an isolated inorganic sandwich-type dimeric POM constructed from two trilacunary Keggin [B-β-SbW₉O₃₃]^9 − moieties and four Sc^3 + ions, while compound 2 shows an extended organic–inorganic hybrid POM which composes of two kinds of distinct tetra-Sc-substituted polyoxotungstate building units and oxalate ligands. Notably, these two compounds also are the first Sc-containing polyoxotungstates based on trilacunary Keggin [B-β-SbW₉O₃₃]^9 − clusters. Electrochemical study showed that compound 2 has good proton conductivity.     

A single‐phase full‐color emitting phosphor Na3Sc2(PO4)3:Eu2+/Tb3+/Mn2+ with near‐zero thermal quenching and high quantum yield for near‐UV converted warm w‐LEDs

A single‐phase full‐color emitting phosphor Na₃Sc₂(PO₄)₃:Eu²⁺/Tb³⁺/Mn²⁺ has been synthesized by high‐temperature solid‐state method. The crystal structure is measured by X‐ray diffraction. The emission can be tuned from blue to green/red/white through reasonable adjustment of doping ratio among Eu²⁺/Tb³⁺/Mn²⁺ ions. The photoluminescence, energy‐transfer efficiency and concentration quenching mechanisms in Eu²⁺‐Tb³⁺/Eu²⁺‐Mn²⁺ co‐doped samples were studied in detail. All as‐obtained samples show high quantum yield and robust resistance to thermal quenching at evaluated temperature from 30 to 200°C. Notably, the wide‐gamut emission covering the full visible range of Na₃Sc₂(PO₄)₃:Eu²⁺/Tb³⁺/Mn²⁺ gives an outstanding thermal quenching behavior near‐zero thermal quenching at 150°C/less than 20% emission intensity loss at 200°C, and high quantum yield‐66.0% at 150°C/56.9% at 200°C. Moreover, the chromaticity coordinates of Na₃Sc₂(PO₄)₃:Eu²⁺/Tb³⁺/Mn²⁺ keep stable through the whole evaluated temperature range. Finally, near‐UV w‐LED devices were fabricated, the white LED device (CCT = 4740.4 K, Ra = 80.9) indicates that Na₃Sc₂(PO₄)₃:Eu²⁺/Tb³⁺/Mn²⁺ may be a promising candidate for phosphor‐converted near‐UV w‐LEDs.