A novel highly thermal-stable red-emitting CaGdSbWO8
Zhang et al. [35] synthesized Ca 1-x Ln x WO 4:Eu 3+ (Ln = Y, Gd) phosphor with scheelite structure and found that adding Ln into the host can effectively improve the emission intensity of phosphors. Li et al. [33] studied the crystal structure and luminescence properties of CaGd 2 (WO 4) 4:Eu 3+ red phosphor. This scheelite-type phosphor shows ...
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Scheelite – Mineral Properties, Photos and Occurrence
Crystal Structure. Scheelite is a calcium tungstate mineral that is the dominant member of a solid solution series between tungsten-rich scheelite (CaWO 4) and rare molybdenum-rich powellite (CaMoO 4), a much less common variant. This solid solution explains why most scheelites contain certain amount of molybdenum in their structure.
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Crystal structure of scheelite CaWO4.
Results of a detailed structural characterization of nominally pure and doped single crystals of scheelite, eulytin, and perovskite families obtained by melt methods were considered and analyzed....
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Shock behavior of zircon: phase transition to scheelite structure and
Transformation to the scheelite structure started above 30 GPa, and was completed above 53 GPa in the case of single crystal specimens. Tetragonal unit cell parameters of the scheelite type ZrSiO 4 at room condition are measured to be a = 4.7341(1)Å, c = 10.51(1)Å, c/a = 2.219(2) and V = 235.5(2)Å 3, which is smaller than that of the zircon ...
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Synthesis and Characterization of a …
According to the present X-ray diffraction results for CsBaGd(MoO 4) 3, the ternary molybdate CsBaGd(MoO 4) 3 has a monoclinically distorted scheelite structure (sp. gr. P2 1 /n, Z = 9). Its X-ray diffraction pattern is very similar in the location of the strongest lines to that of α-KSm(MoO 4) 2, suggesting that the ternary and double molybdates are similar in structural basis.
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Microstructure investigation and fluorescence properties …
It is assumed, that europium is incorporated into the scheelite structure at Sr/Ba sites and charge compensation is achieved by Sr/Ba vacancies. The incorporation of Eu 3+ into the crystals is accompanied by a change in the spectral shape of the Eu 3+ emission spectra.
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The luminescence of uranium‐activated tungstates and …
The luminescence of uranium‐activated tungstates and molybdates with scheelite structure R. U. E. 't Lam; R. U. E. 't Lam Physical Laboratory, State University, P.O. Box 80.000, 3508 TA Utrecht, The Netherlands. Search for other works by this author on: This Site. PubMed.
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Materials Project
CaWO₄ is Zircon-like structured and crystallizes in the tetragonal I4₁/a space group. Ca²⁺ is bonded in a 8-coordinate geometry to eight equivalent O²⁻ atoms. There are four shorter (2.44 Å) and four longer (2.47 Å) Ca-O bond lengths. W⁶⁺ is bonded in a tetrahedral geometry to four equivalent O²⁻ atoms. All W-O bond lengths are 1.80 Å. O²⁻ is bonded in a distorted ...
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Exploring the nature of the fergusonite–scheelite …
A number of metal oxides that crystallise in the scheelite structure type are known to be excellent oxide ion conductors. Here we report the synthesis of a series of materials with general formula LaNb 1−x Mo x O 4+0.5x (x = 0, 0.08, …
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A novel scheelite-like structure of BaBi2Mo4O16: …
The crystal structure along a-axis (Fig. 1) consists of layers of [Bi–O] units and BaO 10 units separated by isolated MoO 4 tetrahedra. The structure can be regarded similar to the scheelite type, ABO 4. Fig. 2 a shows the structure of monoclinic (space group I2/b) BiVO 4 [13], a typical example of the scheelite type
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Understanding the photocatalytic activity of bismuth …
For instant, Z. Zhao et al. [15] revealed that the slightly distorted crystal structure in the monoclinic scheelite structure enhances the effect of Bi-6s states on its optoelectronic properties over other phases, leading to excellent photocatalytic activity. K. Ding et al [16]. studied the photocatalytic activities of different polymorphs.
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A polyacrylamide gel route to photocatalytically active …
Fig. 1 shows the XRD patterns of BiVO 4 samples fabricated using different chelating agents. It is seen that all the samples crystallize in a pure monoclinic scheelite structure of BiVO 4 (PDF card no. 75-1867) with no traces of secondary phase. Fig. 2 shows the SEM images of BiVO 4 samples, revealing that the particles are primarily shaped like spheres. …
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An investigation on novel electrolyte materials with scheelite
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 the ...
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Flotation chemistry of scheelite and its practice: A …
In this paper, the progress and prospects of scheelite flotation chemistry and its practice are summarized, encompassing various fields — such as crystal chemistry, solution …
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The Mineral scheelite
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 mineral Powellite, …
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New nonstoichiometric molybdate, tungstate, and vanadate …
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 3+.5 MO 4 where …
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Dielectric Constants of Scheelite Structure Crystals
W. S. Brower, Jr., P. H. Fang; Dielectric Constants of Scheelite Structure Crystals, Journal of Applied Physics, Volume 40, Issue 12, 1 November 1969, Pages 498
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Structural, lattice vibrational, optical and microwave dielectric
In scheelite structure A- and B-site cations possess coordination number eight and four respectively whereas in wolframite structure both cations possess six coordination numbers. Numerous investigations were reported on scheelite compounds for cathode material in solid oxide fuel cells [8], photo catalytic [9] and photoluminescent materials ...
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Scheelite
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, …
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Electrical properties of scheelite structure ceramic electrolytes for
A novel electrolyte based on Gd doped CaMoO 4 with scheelite structure has been investigated. X-ray diffraction results show that the single-phase scheelite structure can be formed at 900 °C.Electrochemical measurement results indicate that the addition of certain quantity Gd 2 O 3 (x = 0.5) can increase the conductivity of CaMoO 4 obviously. The total …
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Defects, Dopants, and Protons in LaNbO4 | Chemistry of …
Simulation methods have been used to investigate the energetics of defect formation, dopant solution, water incorporation, and defect clustering in the high-temperature proton conductor LaNbO4. The interatomic potential model successfully reproduces the observed tetragonal scheelite-type structure of LaNbO4. Formation of an oxygen vacancy, required for …
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Scheelite trace element compositions: A robust new tool for …
Scheelite (CaWO 4) exhibits a tetragonal crystal structure (space group I41/a, and its crystal structure has two unique cation sites: an [8]-coordinated site, in which alkaline …
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Scheelite – Mineral Properties, Photos and Occurrence
Scheelite is a calcium tungstate mineral that is the dominant member of a solid solution series between tungsten-rich scheelite (CaWO4) and rare molybdenum-rich powellite (CaMoO4), a much less common variant. This solid solution explains why most scheelites contain certain …
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Novel B‐site scheelite structure ceramic Bi(Ge0.5Mo0.5)O4 …
In this work, we report a novel Scheelite structure phase of Bi (Ge 0.5 Mo 0.5)O 4 and a detailed study of both structural analysis and dielectric properties investigation.
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Scheelite Mineral Data
Named after the Swedish chemist, Karl Wilhelm Scheele (1742-1786). Comments: Orange scheelite with white mica. Location: Pingwu, Sichuan, China. Scale: 9.5 x 9 cm. © Fabre …
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Crystal structure of defect scheelite-type Nd2/3[WO4]
Another, formula-analogous polymorph of neodymium(III) ortho-oxidotungstate(VI) with the composition Nd 2 [WO 4] 3 is already known in literature (Weil et al., 2009 #), with this compound crystallizing in the scheelite-derived Eu 2 [WO 4] 3 structure type (space group C2/c; Templeton & Zalkin, 1963 #).The main difference between these polymorphs is the emergence of a fifth, …
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Scheelite, structure type
Scheelite, structure type Some phosphates of the AM2(P04)3 family form other modifications as well neptunium phosphate NaNp2(P04)3 with monazite type structure, Pl ln (this type was obtained by heating the trigonal form in Ar + 5% H2 at 1100 °C [5,35]) neptunium and plutonium phosphates AgNp2(P04)3 and AgPu2(P04)3 with scheelite type structure ...
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PHASES OF SCHEELITE STRUCTURE IN THE SYSTEMS OF …
Mutual solubility of bivalent metal molybdates and tungstates with scheelite structure was theoretically estimated by calculating formation enthalpies and the maximal decomposition temperatures of solid solutions at different temperatures. The theoretical stability of continuous solid solutions in binary systems of bivalent metal molybdates and ...
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Luminescence investigation of Eu3+ activated double …
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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Comparative electrochemical investigation for scheelite …
In summary, scheelite structure metal tungstate like as NiWO 4, CuWO 4 and CoWO 4 were synthesis through chemical reflux method. These prepared materials structural and functional group were analysis through the qualitative tools like XRD and FT-IR. The surfactant C-TAB and PEG-400 is play a vital role to resists the growth of the particles and ...
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