Rondorfite-type structure — XPS and UV–vis study

Journal Article · Thu Oct 15 00:00:00 EDT 2015 · Materials Research Bulletin

DOI:https://doi.org/10.1016/J.MATERRESBULL.2015.06.029· OSTI ID:22475975

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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 by a rotation of silicate tetrahedra within magnesiosilicate pentamer and luminescence disappearance.

• OSTI ID: 22475975
• Journal Information: Materials Research Bulletin, Vol. 70; Other Information: Copyright (c) 2015 Elsevier Science B.V., Amsterdam, The Netherlands, All rights reserved.; Country of input: International Atomic Energy Agency (IAEA); ISSN 0025-5408
• Country of Publication: United States
• Language: English

Related Subjects

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