Temperature dependence of the cation distribution in CuAl2O4.

O'Neill, H. S. C. and James, M. and Dollase, W. A. and Redfern, S. A. T. (2005) Temperature dependence of the cation distribution in CuAl2O4. European Journal of Mineralogy, 17. pp. 581-586. DOI 10.1127/0935-1221/2005/0017-0581

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Abstract

The temperature dependence of the cation distribution in CuAl2O4 spinel has been determined from 600 to 1100°C on quenched specimens by powder X-ray diffraction, and from room temperature to 1000°C by in-situ high-temperature powder neutron diffraction. The results, in agreement with earlier work, show that CuAl2O4 is a largely normal spinel, which is already highly disordered at 600°C, the lowest temperature at which the cation distribution is inferred to be in equilibrium, with an inversion parameter, x, at this temperature of 0.35 ± 0.005 from the neutron diffraction experiments. Increasing temperature to 1000°C only causes a modest increase in x, to 0.40 ± 0.005. This somewhat unusual behaviour may be ascribed to local distortions from the Jahn-Teller effect in both octahedrally and tetrahedrally coordinated Cu2+. Thermodynamically, the ordering may be described either with a large entropy of disordering, or alternatively, with a large and positive quadratic term in the enthalpy of disordering. The Jahn-Teller effect produces no long-range distortion of the structure, which has cubic symmetry (space group Fd–3m) under all investigated conditions

Item Type: Article
Uncontrolled Keywords: 2005 AREP 2005 P IA49
Subjects: 03 - Mineral Sciences
Divisions: 03 - Mineral Sciences
Journal or Publication Title: European Journal of Mineralogy
Volume: 17
Page Range: pp. 581-586
Identification Number: 10.1127/0935-1221/2005/0017-0581
Depositing User: Sarah Humbert
Date Deposited: 25 Aug 2010 10:40
Last Modified: 23 Jul 2013 09:59
URI: http://eprints.esc.cam.ac.uk/id/eprint/1765

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