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Thermal expansion of troilite and pyrrhotite determined by in situ cooling (873 to 373 K) neutron powder diffraction measurements

Tenailleau, Christophe and Etschmann, Barbara and Wang, Hua and Pring, Allan and Grguric, Ben and Studer, Andrew Thermal expansion of troilite and pyrrhotite determined by in situ cooling (873 to 373 K) neutron powder diffraction measurements. (2005) Mineralogical Magazine, vol. 69 (n° 2). pp. 205-216. ISSN 1471-8022

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Official URL: http://dx.doi.org/10.1180/0026461056920247

Abstract

The thermal expansion coefficients for natural troilite, FeS, Ni-rich pyrrhotite, Fe0.84Ni0.11S, and Ni-poor pyrrhotite, Fe0.87Ni0.02S, were measured during cooling by in situ neutron powder diffraction over the temperature range 873–373 K. Between 873 and 573 K, the mean thermal expansion coefficients for the three compositions are 7.4(3) × 10-5 {FeS}, 8.0(4) × 10-5 {Fe0.84Ni0.11S} and 8.5(4) × 10-5 K–1 {Fe0.87Ni0.02S}. Below 573 down to 373 K, the first two increase considerably to 14.1(7) × 10-5 {FeS} and 9.3(5) × 10-5 {Fe0.84Ni0.11S} while the latter sample shows no significant variation, 8.4(5) × 10-5 K-1. Below 573 K, the thermal expansion is highly anisotropic, with Deltaa/100 K-1 ranging from 0.89(9)% {FeS} to 0.48(12)% {Fe0.87Ni0.02S} while Deltac/100 K-1 ranges from -0.39(11)% {FeS} to -0.13(2)% {Fe0.87Ni0.02S}. Upon cooling through 573 K, troilite and pyrrhotite undergo a transition where the FeS6 octahedra distort and in the case of pyrrhotite, cation-vacancy clustering occurs. The thermal expansion coefficients are bigger for low cation-vacancy concentrations and decrease as the pyrrhotites become less stoichiometric. This indicates that the thermal expansion in these minerals is damped by vacancy ordering or clustering. The thermal expansion coefficients for troilite and pyrrhotite are amongst the largest reported for sulphide minerals and their role in the formation of ore textures is discussed briefly.

Item Type:Article
Additional Information:Thanks to The Mineralogical Society editor. The definitive version is available at http://www.minersoc.org/ The original PDF of the article can be found at Mineralogical Magazine website : http://www.ingentaconnect.com/content/minsoc/mag/2005/00000069/00000002/art00010?token=0056118177630504c2a726e2d58464340592f713b672c57582a67232d45232b6c243f6a76577441283e662
Audience (journal):International peer-reviewed journal
Uncontrolled Keywords:
Institution:Other partners > University of Adelaïde (AUSTRALIA)
Other partners > WMC Resources Limited (AUSTRALIA)
Other partners > Australian Nuclear Science and Technology Organisation - ANSTO (AUSTRALIA)
Other partners > South Australian Museum (AUSTRALIA)
Laboratory name:
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Deposited By: Nihad Lahdifi
Deposited On:25 Feb 2011 11:43

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