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Iron oxidation dynamics vs. temperature of synthetic potassic-ferro-richterite: a XANES investigation

DOI: 10.1039/C8CP04249G DOI Help

Authors: G. Della Ventura (University of Roma Tre; INFN-LNF) , F. Galdenzi (University of Roma Tre) , G. Cibin (Diamond Light Source) , R. Oberti (CNR-Istituto di Geoscienze) , Wei Xu (BSRF, Institute of High Energy Physics; Università di Tor Vergata) , S. Macis (INFN-LNF; RICMASS) , Augusto Marcelli (INFN-LNF; Università di Tor Vergata)
Co-authored by industrial partner: No

Type: Journal Paper
Journal: Physical Chemistry Chemical Physics , VOL 167-3

State: Published (Approved)
Published: August 2018
Diamond Proposal Number(s): 12031

Abstract: We investigated the oxidation behaviour of a synthetic potassic-ferro-richterite up to 750 °C by using simultaneous X-ray absorption spectroscopy and X-ray diffraction experiments with synchrotron radiation. From the X-ray diffraction results, we observed an abrupt decrease of cell dimensions at ∼335 °C accompanied by an anomalous increase in the monoclinic cell angle β. From the analysis of the XANES spectra at the iron K-edge, we observed that the structural shrinkage is due to the iron oxidation process, coupled to hydrogen loss, occurring at ∼315 °C, slightly before the cell contraction. Combining these results with previous studies performed on similar samples by single-crystal structure refinement, Mössbauer, high temperature-Fourier transform IR and Raman spectroscopies, we show that the temperature evolution in Fe-amphiboles is a multi-step process. Following the iron oxidation driven by temperature, the structural dynamics in this double-chain silicate is ruled by local strains in the ribbon of iron-filled octahedra, mainly due to the contraction of the M(1) site.

Subject Areas: Chemistry, Earth Science

Instruments: B18-Core EXAFS