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Open AccessArticle

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

1
Institute of Geology of Ore Deposits, Petrography, Mineralogy and Geochemistry (IGEM RAS), 35 Staromonetnyi per., 119017 Moscow, Russia
2
National Research Centre ‘Kurchatov Institute’, 1 Akademika Kurchatova pl., 123182 Moscow, Russia
3
Institute of Experimental Mineralogy (IEM RAS), 142432 Chernogolovka, 142432 Moscow Region, Russia
4
The Rossendorf Beamline at ESRF—The European Synchrotron, CS40220, 38043 Grenoble CEDEX 9, France
5
Helmholtz-Zentrum Dresden-Rossendorf (HZDR), Institute of Resource Ecology, P.O. Box 510119, 01314 Dresden, Germany
6
Department of Chemistry, Lomonosov Moscow State University, 119991 Moscow, Russia
*
Author to whom correspondence should be addressed.
Minerals 2020, 10(7), 640; https://doi.org/10.3390/min10070640
Received: 24 June 2020 / Revised: 13 July 2020 / Accepted: 15 July 2020 / Published: 20 July 2020
(This article belongs to the Special Issue X-ray Absorption Spectroscopy of Synthetic and Natural Minerals)
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.%. View Full-Text
Keywords: sphalerite; synthetic minerals; X-ray absorption spectroscopy; XANES; EXAFS; indium; copper; silver; trace elements sphalerite; synthetic minerals; X-ray absorption spectroscopy; XANES; EXAFS; indium; copper; silver; trace elements
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MDPI and ACS Style

Trofimov, N.D.; Trigub, A.L.; Tagirov, B.R.; Filimonova, O.N.; Evstigneeva, P.V.; Chareev, D.A.; Kvashnina, K.O.; Nickolsky, M.S. The State of Trace Elements (In, Cu, Ag) in Sphalerite Studied by X-Ray Absorption Spectroscopy of Synthetic Minerals. Minerals 2020, 10, 640. https://doi.org/10.3390/min10070640

AMA Style

Trofimov ND, Trigub AL, Tagirov BR, Filimonova ON, Evstigneeva PV, Chareev DA, Kvashnina KO, Nickolsky MS. The State of Trace Elements (In, Cu, Ag) in Sphalerite Studied by X-Ray Absorption Spectroscopy of Synthetic Minerals. Minerals. 2020; 10(7):640. https://doi.org/10.3390/min10070640

Chicago/Turabian Style

Trofimov, Nikolay D.; Trigub, Alexander L.; Tagirov, Boris R.; Filimonova, Olga N.; Evstigneeva, Polina V.; Chareev, Dmitriy A.; Kvashnina, Kristina O.; Nickolsky, Maximilian S. 2020. "The State of Trace Elements (In, Cu, Ag) in Sphalerite Studied by X-Ray Absorption Spectroscopy of Synthetic Minerals" Minerals 10, no. 7: 640. https://doi.org/10.3390/min10070640

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