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Title: Rondorfite-type structure — XPS and UV–vis study

Highlights: • Structural and spectroscopic characterization of chlorosilicate mineral, rondorfite. • Characterization of main photoemission lines and valence band spectra. • The study of color origin’s using UV–vis spectroscopy. • Analysis of structural changes in context of origin of natural fluorescence. • Discussion of a new application possibilities of analyzed mineral - Abstract: This paper focuses on X-ray diffraction, X-ray photoelectron and UV–vis spectroscopy of two different (green, orange) rondorfite samples. The differences in the sample color originate from various O/Cl ratios. The orange color was found to be related either to the isomorphic substitution of Fe{sup 3+}/Al{sup 3+} for Mg{sup 2+}, the presence of atypical [MgO{sub 4}] tetrahedrons in crystal structure or electronegativity of the sample. The tetrahedron is known to be very prone to accumulation of impurities and substitute atoms. Moreover, the XPS data showed tetrahedrally coordinated Mg{sup 2+} and isomorphic substitution of Al{sup 3+}/Fe{sup 3+} for Mg{sup 2+}, which influences local disordering and the point defects density and distribution. Non-equilibrium chlorine positions inside the crystal cages as well as Ca-Cl bonds have also been found. The XPS measurements as a function of temperature indicate occurrence of a structural transformation at about 770 K which is accompanied bymore » a rotation of silicate tetrahedra within magnesiosilicate pentamer and luminescence disappearance.« less
Authors:
 [1] ;  [2] ;  [3] ;  [2] ;  [2] ;  [1] ;  [2] ;  [3] ;  [2] ;  [3] ;  [3] ;  [2] ;  [3] ;  [2] ;
  1. Institute of Material Science, University of Silesia, 75 Pułku Piechoty 1a, 41-500 Chorzow (Poland)
  2. (Poland)
  3. A.Chelkowski Institute of Physics, University of Silesia, Uniwersytecka 4, 40-007 Katowice (Poland)
Publication Date:
OSTI Identifier:
22475975
Resource Type:
Journal Article
Resource Relation:
Journal Name: Materials Research Bulletin; Journal Volume: 70; Other Information: Copyright (c) 2015 Elsevier Science B.V., Amsterdam, The Netherlands, All rights reserved.; Country of input: International Atomic Energy Agency (IAEA)
Country of Publication:
United States
Language:
English
Subject:
36 MATERIALS SCIENCE; ALUMINIUM IONS; CHLORINE COMPOUNDS; COLOR; CRYSTAL DEFECTS; ELECTRONEGATIVITY; FLUORESCENCE; IRON IONS; MAGNESIUM IONS; MAGNESIUM OXIDES; MINERALS; PHOTOEMISSION; POINT DEFECTS; SILICATES; SPECTROSCOPY; TEMPERATURE DEPENDENCE; ULTRAVIOLET RADIATION; VALENCE; VISIBLE RADIATION; X-RAY DIFFRACTION; X-RAY PHOTOELECTRON SPECTROSCOPY