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Scheelite, calcium tungstate mineral, CaWO4, that is an important ore of tungsten. It acquired commercial value in the 20th century when tungsten became used in alloy steels and electric-light filaments. The mineral is …
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The observed significant distortion in the monoclinic scheelite structure enhances the local polarization that leads to better electrons and holes separation and superior photoelectrocatalytic ...
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With the depletion of wolframite, scheelite has become the main source of tungsten resources worldwide. Scheelite is mainly recovered by flotation, a mineral …
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Empirical Formula: Ca (WO 4) Environment: A primary tunsten ore mineral commonly found in contact-metamorphic deposits, high-temperature hydrothermal veins, greisens, …
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In the scheelite structure, Na, Sr and Re atoms occupy the 4b Wyckoff position collectively, while W atoms occupy the 4a Wyckoff position. Based on the scheelite structure characteristics and ionic radii considerations, the current findings are deemed credible. Furthermore, the tetrahedral and octahedral bond lengths in Table S1 exhibit a ...
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The main peaks of scheelite structure are found in the XRD chart, indicating that Sm 3+ has all entered the lattice of strontium tungsten molybdate, and formed a uniform single-phase solid solution with scheelite structure. At the same time, some weak diffraction peaks were observed besides the scheelite main phase. This may be due to …
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The phase structures of pristine CaWO 4 and Ce/Fe–CaWO 4 photocatalysts were investigated by XRD measurement and the obtained results are presented in Fig. 1.In the XRD pattern of bare CaWO 4, the main diffraction peaks were in good agreement with the standard JCPDS data card 72–1624 [16], indicating the successfully formation of …
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The scheelite crystal structure also allows incorporation of other elements, such as Na, Pb, Fe, Ba, Th, Ti, and Rb. The abundance of these elements in scheelite can be affected by many factors. For example, previous studies have evaluated the mineral-melt partition coefficients of REEs ( Li et al., 2018, Zhang et al., 2018, Su et al., 2020 ).
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Scheelite solubility increases greatly below pH 6. Above pH 6, the molar concentration of WO 4 2− ions is much greater than Ca 2+, exhibiting therefore a differentiated dissolution theoretically incompatible with the structure of …
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NSLW scheelite structure compounds have been studied as fluorescent materials, however, their researches in the field of microwave dielectric ceramics are still in a blank state. Based on this, a ternary tungstate NSLW microwave dielectric ceramics with scheelite structure were successfully synthesized by a conventional solid state reaction ...
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E i n e Reihe von Phospha t en, Arsenaten, Vanada t en, Tan t a l a t en u n d Niobat en wurden Drucken bis 80.000 A t m . und T e m p e r a t u r e n bis 600°C un te rwor fen . Die S t r u k t u r e n der Hochdruckphasen wurden nach,,Abschrecken" auf Zimmert e m p e r a t u r durch Röntgenstrahlbevigung bes t immt . Die Mehrzahl der Arsena te (Sm bis Lu) …
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scheelite, calcium tungstate mineral, CaWO 4, that is an important ore of tungsten.It acquired commercial value in the 20th century when tungsten became used in alloy steels and electric-light filaments. The mineral is named in honour of the Swedish chemist Carl Wilhelm Scheele, who obtained tungstic acid from it in 1781.Scheelite commonly occurs …
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They have a defect scheelite-type 3D structure (space group I4 1 /a) with a random distribution of Li + (Na +), Gd 3+, and vacancies in the crystal. A Na 2/7 Gd 4/7 MoO 4 single crystal with ...
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Scheelite has a distinctive tetragonal crystal structure, with its crystals often appearing as elongated prisms or flat tabular shapes. It is commonly found in hydrothermal veins, skarns, and greisen deposits associated with granitic intrusions.
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A comprehensive approach to understanding the electronic structure of monoclinic scheelite bismuth vanadate (ms-BiVO4), including both valence band (VB) and conduction band (CB) orbital character, is presented. Density functional theory (DFT) calculations are directly compared to experimental data obtained via X-ray absorption …
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Scheelite is an abundant tungstate mineral known for its blue fluorescence. Though gems are rare, they exhibit impressive sparkle and various colors. ... Crystal structure: Tetragonal. Luster: Adamantine (diamond-like) or vitreous (glassy) Transparency: Transparent to opaque. Refractive index: 1.91-1.93. Density: 5.90-6.3.
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The result shows that the phosphor shares the same tetragonal scheelite structure as NaEu(MoO 4) 2, with cation disorder. The XRD pattern of KEu(MoO 4) 2 (b), which is consistent with JCPDS31-1006 [KEu(MoO 4) 2], is different from the curve a. It shows KEu(MoO 4) 2 has an ordered scheelite structure which is triclinic [15], [17].
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The trace element composition of scheelite from 19 well-documented reduced and oxidized skarn systems was measured by laser ablation-inductively coupled plasma-mass spectrometry (LA-ICP-MS) to establish chemical criteria for the application of scheelite as an efficient indicator mineral for mineral exploration targeting. In both …
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Scheelite CaWO4 c 2001-2005 Mineral Data Publishing, version 1 Crystal Data: Tetragonal. Point Group: 4/m. Crystals are typically pseudo-octahedral {011} or {112}, with modifying forms {001}, {013}, {121}, several others, to 32 cm; commonly granular, massive. Twinning: {110}, common, penetration and contact twins, composition plane {110} or {001}.
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A novel electrolyte based on Gd doped CaMoO4 with scheelite structure has been investigated. X-ray diffraction results show that the single-phase scheelite structure can be formed at 900 °C.
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BiVO4 powder with scheelite structure was obtained by hydrolyzing a nitric acid solution of Bi(NO3)3 and Na3VO4 with bases (Na2CO3 and NaHCO3) at room temperature. Tetragonal BiVO4 of a high-temperature form was obtained after 4.5 h of preparation time while monoclinic BiVO4 was done after 46 h. Although the structure …
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Scheelite is an important ore mineral, and is well-known among collectors for its distinctly colored crystals associated with brilliant fluorescence. It forms a series with the rarer …
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Scheelite CaWO4. c 2001-2005 Mineral Data Publishing, version 1. Crystal Data: Tetragonal. Point Group: 4/m. Crystals are typically pseudo-octahedral {011} or {112}, …
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Crystal Structure. Scheelite is a calcium tungstate mineral that is the dominant member of a solid solution series between tungsten-rich scheelite (CaWO 4) …
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The crystal structure of scheelite belongs to the tetragonal system, with a space group of I4 1 /a and cell parameters of a = b = 0.5243 nm, c = 1.1376 nm, α = β = γ = 90°, and Z = 4 (Gao et al., 2016b).As shown in Fig. 1 (a), the complex anion in the crystal is a W–O 4 tetrahedron, formed by the combination of W 6+ and four O 2-and Ca 2+ ions, …
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The scheelite structure can be described as two intercalated diamond lattices, one for A cations and the other for B cations. The A cations are coordinated by eight oxygen …
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Scheelite is defined as a mineral that is a significant source of tungsten, known for its blue color under UV light which changes to orange with increasing molybdenum content. It is …
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1. Introduction. In the scheelite structure, the Ca 2+ exists as a bisdisphenoid polyhedron with eight oxygen atoms forming a CaO 8 polyhedron, whereas the molybdenum (Mo) ions are surrounded by four oxygen atoms forming a tetrahedral unit. The CaO 8 polyhedron shares four of its edges with four other CaO 8 polyhedra …
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Phases of the formula A 1−x фxMO 4 with the scheelite-type structure are described where ф represents a vacancy at the A cation site and M is Mo 6+, W 6+, and/or V 5+.Many different univalent, divalent, and trivalent A cations were used in this study. The phases with no defects, i.e., x = 0, were known except for those of the type A 1+.5 A …
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The chemical composition of scheelite is calcium tungstate, with the chemical formula CaWO4. It consists of calcium (Ca) cations and tungstate (WO4) anions. The tungstate anion contains one tungsten atom (W) bonded to four oxygen atoms (O). The calcium cation is coordinated with …
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