High-temperature breakdown of the synthetic iodine analogue of vanadinite, Pb5(VO4)3I: an apatite-related compound for iodine radioisotope immobilization?

Redfern, S. A. T. and Smith, S. E. and Maddrell, E. R. (2012) High-temperature breakdown of the synthetic iodine analogue of vanadinite, Pb5(VO4)3I: an apatite-related compound for iodine radioisotope immobilization? Mineralogical Magazine, 76 (4). pp. 997-1003. ISSN 0026-461X, Online ISSN: 1471-8022 DOI 10.1180/minmag.2012.076.4.15

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Official URL: http://minmag.geoscienceworld.org/content/76/4/997

Abstract

The thermal stability of the synthetic iodine analogue of vanadinite, Pb5(VO4)3I, in air has been investigated by in situ high temperature X-ray powder diffraction between 300 and 1070 K. Rietveld refinement of phase fractions shows that breakdown to lead orthovanadate, Pb3(VO4)2, begins at temperatures above 540 K, with complete loss of iodine above 680 K. More than 50 K below the onset of breakdown, the unit-cell parameters of Pb5(VO4)3I show anomalous contraction in the crystallographic x–y plane (reduction of a) which we associate with movement of iodine within the [0001] channels of the structure. The implications of these results for immobilization of 129I in potential apatite-related crystalline radioactive waste forms are discussed.

Item Type: Article
Uncontrolled Keywords: 2012AREP; IA64;
Subjects: 03 - Mineral Sciences
Divisions: 03 - Mineral Sciences
Journal or Publication Title: Mineralogical Magazine
Volume: 76
Page Range: pp. 997-1003
Identification Number: 10.1180/minmag.2012.076.4.15
Depositing User: Sarah Humbert
Date Deposited: 07 Aug 2012 10:57
Last Modified: 23 Jul 2013 10:04
URI: http://eprints.esc.cam.ac.uk/id/eprint/2579

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