Ca3WO6 prepared by roasting tungsten-containing materials and its leaching performance

Li, Xiaobin; Xu, Xiangming; Zhou, Qiusheng; Qi, Tiangui; Liu, Guihua; Peng, Zhihong; Cui, Yuanfa; Li, Jianpu

doi:10.1016/j.ijrmhm.2015.06.003

Cited by 25 publications

(5 citation statements)

References 23 publications

Supporting

Mentioning

Contrasting

Order By: Relevance

“…Ca 3 WO 6 and Ca 2.98 Eu 0.02 WO 6 powders were synthesized by the traditional solid-state reaction method. A batch powder with a 3.2/1 molar ratio of CaCO 3 /WO 3 was mixed for 12 h with ethanol and a ZrO 2 milling ball, and calcined at 1200 °C for 12 h in an alumina crucible, after drying at 80°C [ 16 ]. CaWO 6 powder also gained from the same powder calcination procedure.…”

Section: Experimentalsmentioning

confidence: 99%

Thermal Evolutions to Glass-Ceramics Bearing Calcium Tungstate Crystals in Borate Glasses Doped with Photoluminescent Eu3+ Ions

et al. 2021

View full text Add to dashboard Cite

Thermal evolutions of calcium-tungstate-borate glasses were investigated for the development of luminescent glass-ceramics by using Eu3+ dopant in a borate glass matrix with calcium tungstate, which was expected to have a combined character of glass and ceramics. This study revealed that single-phase precipitation of CaWO4 crystals in borate glass matrix was possible by heat-treatment at a temperature higher than glass transition temperature Tg for (100−x) (33CaO-67B2O3)−xCa3WO6 (x = 8−15 mol%). Additionally, the crystallization of CaWO4 was found by Raman spectroscopy due to the formation of W=O double bondings of WO4 tetrahedra in the pristine glass despite starting with the higher calcium content of Ca3WO6. Eu3+ ions were excluded from the CaWO4 crystals and positioned in the borate glass phase as a stable site for them, which provided local environments in higher symmetry around Eu3+ ions.

show abstract

Section: Experimentalsmentioning

confidence: 99%

Thermal Evolutions to Glass-Ceramics Bearing Calcium Tungstate Crystals in Borate Glasses Doped with Photoluminescent Eu3+ Ions

et al. 2021

View full text Add to dashboard Cite

show abstract

“…established that decreasing the Ca/W ratio induces the formation of the CaWO 4 phase. [ 36 ] In this study, the same reasoning can be applied to the emergence of the CaWO 4 phase.…”

Section: Resultsmentioning

confidence: 99%

Eu³⁺ Site Distribution and Local Distortion of Photoluminescent Ca₃WO₆:(Eu³⁺, K⁺) Double Perovskites as High‐Color‐Purity Red Phosphors

Otsuka,

Oka,

Hayakawa

2023

Advanced Science

View full text Add to dashboard Cite

In this study, Eu3+ and K+ co‐doped Ca3WO6 double perovskite, a high‐color‐purity red phosphor, is quantitatively investigated using synchrotron X‐ray diffraction Rietveld refinement, energy dispersive X‐ray spectroscopy, and high‐resolution PL spectroscopy. The Eu3+ fluorescence line‐narrowing (FLN) results, used to estimate the Eu3+ occupation at given sites (so‐called A and B sites) in the host crystal (A2BMO6; A, B = Ca; M = W), reveal that the Eu3+ ions have a twin distribution in both the A and B sites with high asymmetry ratios of ΛA = 9.7 and ΛB = 10.7, respectively. More interestingly, at lower Eu3+ doping levels, the ions are predominantly located at the B sites (≈75%), indicating that the high color purity of Ca3WO6:(Eu3+, K+) is mainly caused by the high asymmetry ratios of the Eu3+ sites. Rietveld refinement combined with the FLN technique provides more reliable results for increasing the Eu3+ substitution at the A site with Eu3+ and K+ doping concentrations, which lower the lattice energy of Ca3WO6:(Eu3+, K+). The structural distortions owing to K+ co‐doping in terms of the quadratic elongation and bond‐angle variance exhibit good correlations with the Ca(Eu)O12 A‐site cuboctahedra and Ca(Eu)O6 B‐site octahedra, partially accounting for the higher Λ values.

show abstract

“…The phase analyses were performed by a X-ray diffractometer (D8-Advance; Bruker) using a Cu-Kα with 0.0085° step size at a scan rate of 1°• min -1 . The phase fractions of the solid converted products (Y), only taking in account the tungsten-containing species, were calculated semi-quantitatively by the relative intensity ratio method with less than 5% error range; 18 the details for data processing were described in our previous work 15,19 . The conversion ratios (η) of CaWO4 and (Fe,Mn)WO4 to H2WO4…”

Section: Procedures and Measurementmentioning

confidence: 99%

Wolframite Conversion in Treating a Mixed Wolframite–Scheelite Concentrate by Sulfuric Acid

Shen

Zhou

et al. 2017

JOM

Self Cite

View full text Add to dashboard Cite

Complete wolframite conversion in sulfuric acid is significant for expanding the applicability of the sulfuric acid method for producing ammonium paratungstate. In this paper, the conversion of wolframite in treating a mixed wolframite-scheelite concentrate by sulfuric acid was studied systematically. The results show that the conversion of wolframite in sulfuric acid is more difficult than that of scheelite, requiring rigorous reaction conditions. A solid H2WO4 layer forms on the surfaces of the wolframite particles and becomes denser with increasing H2SO4 concentration, thus hindering the conversion. Furthermore, the difficulty in wolframite conversion can be mainly attributed to the accumulation of Fe 2+ (and/or Mn 2+) in the H2SO4 solution, which can be solved by reducing Fe 2+ (and/or Mn 2+) concentration through oxidization and/or a two-stage process. Additionally, the solid converted product of the mixed wolframite-scheelite concentrate has an excellent leachability of tungsten in an aqueous ammonium carbonate solution at ambient temperature, with approximately 99% WO3 recovery. This work presents a route for manufacturing ammonium paratungstate by treating the mixed concentrate in sulfuric acid followed by leaching in ammonium carbonate solution.

show abstract

Ca3WO6 prepared by roasting tungsten-containing materials and its leaching performance

Cited by 25 publications

References 23 publications

Thermal Evolutions to Glass-Ceramics Bearing Calcium Tungstate Crystals in Borate Glasses Doped with Photoluminescent Eu3+ Ions

Thermal Evolutions to Glass-Ceramics Bearing Calcium Tungstate Crystals in Borate Glasses Doped with Photoluminescent Eu3+ Ions

Eu³⁺ Site Distribution and Local Distortion of Photoluminescent Ca₃WO₆:(Eu³⁺, K⁺) Double Perovskites as High‐Color‐Purity Red Phosphors

Wolframite Conversion in Treating a Mixed Wolframite–Scheelite Concentrate by Sulfuric Acid

Contact Info

Product

Resources

About

Ca3WO6 prepared by roasting tungsten-containing materials and its leaching performance

Cited by 25 publications

References 23 publications

Thermal Evolutions to Glass-Ceramics Bearing Calcium Tungstate Crystals in Borate Glasses Doped with Photoluminescent Eu3+ Ions

Thermal Evolutions to Glass-Ceramics Bearing Calcium Tungstate Crystals in Borate Glasses Doped with Photoluminescent Eu3+ Ions

Eu3+ Site Distribution and Local Distortion of Photoluminescent Ca3WO6:(Eu3+, K+) Double Perovskites as High‐Color‐Purity Red Phosphors

Wolframite Conversion in Treating a Mixed Wolframite–Scheelite Concentrate by Sulfuric Acid

Contact Info

Product

Resources

About

Eu³⁺ Site Distribution and Local Distortion of Photoluminescent Ca₃WO₆:(Eu³⁺, K⁺) Double Perovskites as High‐Color‐Purity Red Phosphors