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The microstructure and stoichiometry of pyrite FeS2−x

Published online by Cambridge University Press:  31 January 2011

S. Fiechter*
Affiliation:
Hahn-Meitner-Institut, Bereich “Photochemische Energieumwandlung” Glienicker Staβe 100, D-1000 Berlin 39, Germany
M. Birkholz
Affiliation:
Hahn-Meitner-Institut, Bereich “Photochemische Energieumwandlung” Glienicker Staβe 100, D-1000 Berlin 39, Germany
A. Hartmann
Affiliation:
Hahn-Meitner-Institut, Bereich “Photochemische Energieumwandlung” Glienicker Staβe 100, D-1000 Berlin 39, Germany
P. Dulski
Affiliation:
Hahn-Meitner-Institut, Bereich “Photochemische Energieumwandlung” Glienicker Staβe 100, D-1000 Berlin 39, Germany
M. Giersig
Affiliation:
Hahn-Meitner-Institut, Bereich “Photochemische Energieumwandlung” Glienicker Staβe 100, D-1000 Berlin 39, Germany
H. Tributsch
Affiliation:
Hahn-Meitner-Institut, Bereich “Photochemische Energieumwandlung” Glienicker Staβe 100, D-1000 Berlin 39, Germany
R.J.D. Tilley
Affiliation:
School of Engineering, University of Wales, College of Cardiff, Cardiff CF2 1XH, Great Britain
*
a)Address correspondence to this author.
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Abstract

Both natural and synthetic crystals of pyrite, FeS2−x, have been analyzed chemically and examined structurally by transmission electron microscopy and x-ray powder diffraction. Chemical analysis and density measurements have shown the synthetic crystals, grown at 850 K, are frequently deficient in sulfur, with a composition of FeS2−x with x ⋚ 0.15. From a refinement of the pyrite structure using the integral intensities of the x-ray powder pattern, a variation in the sulfur population parameter was obtained ranging from 0.87(2) to 1.03(3). A correlation according to Vegard's rule between the population factor and the lattice parameter a0 has been proven. Transmission electron microscope examination revealed that the crystals did not contain a significant population of disorder defects which may account for this apparent sulfur deficit. Therefore the nonstoichiometry in pyrite has to be interpreted in terms of S vacancies which can be understood as the tendency of the material to reduce the high anion content in the unit cell. The structural nature of nonstoichiometric pyrite is discussed in relationship to other related disulfides.

Type
Articles
Copyright
Copyright © Materials Research Society 1992

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