Substitution mechanisms in In-, Au-, and Cu-bearing sphalerites studied by X-ray absorption spectroscopy of synthetic compounds and natural minerals

2019 ◽  
Vol 83 (03) ◽  
pp. 435-451 ◽  
Author(s):  
Olga N. Filimonova ◽  
Alexander L. Trigub ◽  
Dmitriy E. Tonkacheev ◽  
Max S. Nickolsky ◽  
Kristina O. Kvashnina ◽  
...  
Keyword(s):  
Solid Solution ◽  
Absorption Spectroscopy ◽  
Trace Element Distribution ◽  
High Tech ◽  
Ionic Radii ◽  
Synthetic Compounds ◽  
X Ray ◽  
Solution State ◽  
X Ray Absorption ◽  
Group 11 Metals

AbstractSphalerite is the main source of In – a ‘critical’ metal widely used in high-tech electronics. In this mineral the concentration of In is commonly correlated directly with Cu content. Here we use X-ray absorption spectroscopy of synthetic compounds and natural crystals in order to investigate the substitution mechanisms in sphalerites where In is present, together with the group 11 metals. All the admixtures (Au, Cu, In) are distributed homogeneously within the sphalerite matrix, but their structural and chemical states are different. In all the samples investigated In3+ replaces Zn in the structure of sphalerite. The In ligand distance increases by 0.12 Å and 0.09–0.10 Å for the 1st and 2nd coordination shells, respectively, in comparison with pure sphalerite. The In–S distance in the 3rd coordination shell is close to the one of pure sphalerite. Gold in synthetic sphalerites is coordinated with sulfur (NS = 2.4–2.5, RAu–S = 2.35 ± 0.01 Å). Our data suggest that at high Au concentrations (0.03–0.5 wt.%) the Au2S clusters predominate, with a small admixture of the Au+ solid solution with an Au–S distance of 2.5 Å. Therefore, the homogeneous character of a trace-element distribution, which is commonly observed in natural sulfides, does not confirm formation of a solid solution. In contrast to Au, the presence of Cu+ with In exists only in the solid-solution state, where it is tetrahedrally coordinated with S atoms at a distance of 2.30 ± 0.03 Å. The distant coordination shells of Cu are disordered. These results demonstrate that the group 11 metals (Cu, Ag and Au) can exist in sphalerite in the metastable solid-solution state. The solid solution forms at high temperature via the charge compensation scheme 2Zn2+↔Me++Me3+. The final state of the trace elements at ambient temperature is governed by the difference in ionic radii with the main component (Zn), and concentration of admixtures.

scholarly journals The State of Trace Elements (In, Cu, Ag) in Sphalerite Studied by X-Ray Absorption Spectroscopy of Synthetic Minerals

Minerals ◽  
2020 ◽  
Vol 10 (7) ◽  
pp. 640 ◽  
Author(s):  
Nikolay D. Trofimov ◽  
Alexander L. Trigub ◽  
Boris R. Tagirov ◽  
Olga N. Filimonova ◽  
Polina V. Evstigneeva ◽  
...  
Keyword(s):  
Solid Solution ◽  
Oxidation State ◽  
Absorption Spectroscopy ◽  
Atomic Structure ◽  
Salt Flux ◽  
Ionic Radii ◽  
Edge Structure ◽  
X Ray ◽  
X Ray Absorption ◽  
Exafs Spectra

The oxidation state and local atomic environment of admixtures of In, Cu, and Ag in synthetic sphalerite crystals were determined by X-ray absorption spectroscopy (XAS). The sphalerite crystals doped with In, Cu, Ag, In–Cu, and In–Ag were synthesized utilizing gas transport, salt flux, and dry synthesis techniques. Oxidation states of dopants were determined using X-ray absorption near edge structure (XANES) technique. The local atomic structure was studied by X-ray absorption fine structure spectroscopy (EXAFS). The spectra were recorded at Zn, In, Ag, and Cu K-edges. In all studied samples, In was in the 3+ oxidation state and replaced Zn in the structure of sphalerite, which occurs with the expansion of the nearest coordination shells due to the large In ionic radius. In the presence of In, the oxidation state of Cu and Ag is 1+, and both metals can form an isomorphous solid solution where they substitute for Zn according to the coupled substitution scheme 2Zn2+ ↔ Me+ + In3+. Moreover, Ag K-edges EXAFS spectra fitting, combined with the results obtained for In- and Au-bearing sphalerite shows that the Me-S distances in the first coordination shell in the solid solution state are correlated with the ionic radii and increase in the order of Cu < Ag < Au. The distortion of the atomic structure increases in the same order. The distant (second and third) coordination shells of Cu and Ag in sphalerite are split into two subshells, and the splitting is more pronounced for Ag. Analysis of the EXAFS spectra, coupled with the results of DFT (Density Function Theory) simulations, showed that the In–In and Me+–In3+ clustering is absent when the metals are present in the sphalerite solid solution. Therefore, all studied admixtures (In, Cu, Ag), as well as Au, are randomly distributed in the matrix of sphalerite, where the concentration of the elements in the “invisible” form can reach a few tens wt.%.

On X-Ray Diffraction and X-Ray Absorption Spectroscopy Characterization of Ball Milled Iron Copper Solid Solution

1998 ◽  
Vol 269-272 ◽  
pp. 473-478 ◽  
Author(s):  
Francsco Cardellini ◽  
Vittoria Contini ◽  
Gregorio D'Agostino ◽  
Adriano Filipponi
Keyword(s):  
Solid Solution ◽  
Absorption Spectroscopy ◽  
X Ray Diffraction ◽  
X Ray ◽  
Iron Copper ◽  
X Ray Absorption

scholarly journals Observation of Chemical State for Interstitial Solid Solution of Carbon in Low-carbon Steel by Soft X-ray Absorption Spectroscopy

2020 ◽  
Vol 60 (1) ◽  
pp. 114-119 ◽  
Author(s):  
Kakeru Ninomiya ◽  
Kazutaka Kamitani ◽  
Yusuke Tamenori ◽  
Kazuki Tsuruta ◽  
Toshihiro Okajima ◽  
...  
Keyword(s):  
Solid Solution ◽  
Carbon Steel ◽  
Absorption Spectroscopy ◽  
Low Carbon Steel ◽  
Chemical State ◽  
Low Carbon ◽  
Interstitial Solid Solution ◽  
X Ray ◽  
X Ray Absorption

scholarly journals Analysis of the dynamic behavior and local structure of solid-solution carbon in age-hardened low-carbon steels by soft X-ray absorption spectroscopy

Materialia ◽  
2020 ◽  
Vol 14 ◽  
pp. 100876
Author(s):  
Kakeru Ninomiya ◽  
Kazutaka Kamitani ◽  
Yusuke Tamenori ◽  
Kazuki Tsuruta ◽  
Ken Takata ◽  
...  
Keyword(s):  
Solid Solution ◽  
Dynamic Behavior ◽  
Absorption Spectroscopy ◽  
Local Structure ◽  
Carbon Steels ◽  
Low Carbon ◽  
Low Carbon Steels ◽  
X Ray ◽  
X Ray Absorption

Operando X-ray Absorption Spectroscopy Identifies a Monoclinic ZrO2:In Solid Solution as the Active Phase for the Hydrogenation of CO2 to Methanol

ACS Catalysis ◽  
2020 ◽  
Vol 10 (17) ◽  
pp. 10060-10067 ◽  
Author(s):  
Athanasia Tsoukalou ◽  
Paula M Abdala ◽  
Andac Armutlulu ◽  
Elena Willinger ◽  
Alexey Fedorov ◽  
...  
Keyword(s):  
Solid Solution ◽  
Absorption Spectroscopy ◽  
Active Phase ◽  
Monoclinic Zro2 ◽  
X Ray ◽  
Hydrogenation Of Co2 ◽  
X Ray Absorption

scholarly journals Observation of Chemical State for Interstitial Solid Solution of Carbon in Low-carbon Steel by Soft X-ray Absorption Spectroscopy

2018 ◽  
Vol 104 (11) ◽  
pp. 628-633 ◽  
Author(s):  
Kakeru Ninomiya ◽  
Kazutaka Kamitani ◽  
Yusuke Tamenori ◽  
Kazuki Tsuruta ◽  
Toshihiro Okajima ◽  
...  
Keyword(s):  
Solid Solution ◽  
Carbon Steel ◽  
Absorption Spectroscopy ◽  
Low Carbon Steel ◽  
Chemical State ◽  
Low Carbon ◽  
Interstitial Solid Solution ◽  
X Ray ◽  
X Ray Absorption

Cu and Zn ordering in aurichalcite

1996 ◽  
Vol 60 (403) ◽  
pp. 887-896 ◽  
Author(s):  
J. M. Charnock ◽  
P. F. Schofield ◽  
C. M. B. Henderson ◽  
G. Cressey ◽  
B. A. Cressey
Keyword(s):  
Solid Solution ◽  
Absorption Spectroscopy ◽  
X Ray Diffraction ◽  
Rich Region ◽  
X Ray ◽  
Metal Site ◽  
Trigonal Bipyramidal ◽  
Jahn Teller ◽  
X Ray Absorption ◽  
Cu And Zn

AbstractThe advantages of X-ray absorption spectroscopy have been utilized to assess the Cu and Zn ordering in aurichalcite, (Cu5−xZnx)(OH)6(CO3)2. We have examined one hydrozincite sample and three aurichalcite samples in which the Cu:Zn ratios are in the range 1:3 to 2:3. Copper 2p XAS confirms that there is no monovalent copper in aurichalcite and that in each sample the copper might be distributed across more than one metal site. EXAFS, at the Cu and Zn K-edges, shows that the copper atoms preferentially enter the Jahn-Teller elongated, octahedral (M2) and trigonal bipyramidal (M4) sites, with the zinc atoms entering the more regular octahedral (M1) and tetrahedral (M3) site. Substantial solid solution towards the zinc rich region is facilitated by the substitution of copper by zinc on the M2 and M4 sites. This information, not easily obtained by X-ray diffraction, substantially enhances the understanding of the structure of aurichalcite.

The State of Platinum in Pyrite Studied by X-Ray Absorption Spectroscopy of Synthetic Crystals

2019 ◽  
Vol 114 (8) ◽  
pp. 1649-1663 ◽  
Author(s):  
Olga N. Filimonova ◽  
Maximilian S. Nickolsky ◽  
Alexander L. Trigub ◽  
Dmitriy A. Chareev ◽  
Kristina O. Kvashnina ◽  
...  
Keyword(s):  
Electron Microscopy ◽  
Solid Solution ◽  
Absorption Spectroscopy ◽  
The State ◽  
Salt Flux ◽  
Chemical Modeling ◽  
Processing Technologies ◽  
X Ray ◽  
The Matrix ◽  
X Ray Absorption

Abstract Pyrite (FeS2) is a typical container of Pt in ores of magmatic and hydrothermal origin and in some carbonrich ores of sedimentary-diagenetic origin. Knowledge of the state of Pt disseminated in the matrix of pyrite, including local atomic environment (type of atoms in the nearest and distant coordination shells, coordination numbers, interatomic distances) and oxidation state, is necessary for physical-chemical modeling of platinum group element mineralization and for the improvement of Pt ore extraction and processing technologies. Here we report results of an investigation of local atomic structure of synthetic Pt-bearing pyrites by means of X-ray absorption spectroscopy (XAS). Synthesis experiments, performed at 580° and 590°C in a Pt-saturated system by means of salt-flux method, yielded crystals of pyrite with concentrations of Pt up to 4 wt %. Scanning electron microscopy (SEM) and electron probe microanalysis (EPMA) showed that the distribution of Pt within the pyrite grains is of zonal character, but within the distinct zones Pt is distributed homogeneously. Negative correlation between the concentrations of Pt and Fe was observed in the synthesized pyrite grains. The slope of the correlation line corresponds to the formation of the solid solution in the Pt-Fe-S system and/or to the formation of PtS2. The XAS experiments revealed the existence of two forms of Pt in pyrite. The main form is the solid solution Pt(IV), which isomorphically substitutes for Fe. The Pt-S distance in pyrite is ~0.1 Å longer than that of Fe-S in pure pyrite. The distortion of the pyrite crystal structure disappears at R >2.5 Å. The second Pt-rich form was identified by means of high-resolution transmission electron microscopy (HRTEM) as nanosized inclusions of PtS2. Heating experiments with in situ registration of X-ray absorption spectra resulted in partial decomposition (dissolution) of PtS2 nanosized inclusions with the formation of the solid solution (Fe1–xPtx)S2. Therefore, the PtS2 nanosized particles can be considered as a quench product. Our data demonstrate that both Pt solid solution and PtS2 nanosized inclusions (at high Pt content) can exist in natural Pt-bearing pyrites.

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