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Alpha particle damage in biotite characterized by microfocus X-ray diffraction and Fe<I>K</I>-edge X-ray absorption spectroscopy

DOI: 10.1180/minmag.2013.077.6.12 DOI Help

Authors: Richard Pattrick (University of Manchester) , John Charnock (University of Manchester) , Tina Geraki (Diamond Light Source) , Fred Mosselmans (Diamond Light Source) , Carolyn Pearce (University of Manchester) , Simon Pimblott (University of Manchester) , Giles Droop (University of Manchester)
Co-authored by industrial partner: No

Type: Journal Paper
Journal: Mineralogical Magazine , VOL 77 (6) , PAGES 2867 - 2882

State: Published (Approved)
Published: August 2013
Diamond Proposal Number(s): 585

Abstract: Combined microfocus XAS and XRD analysis of alpha-particle radiation damage haloes around thorium-containing monazite in Fe-rich biotite reveals changes in both short- and long-range order. The total alpha-particles flux derived from the Th and U in the monazite over 1.8 Ga was 0.022 alpha particles per atomic component of the monazite and this caused increasing amounts of structural damage as the monazite emitter is approached. Short-range order disruption revealed by Fe K-edge EXAFS is manifest by a high variability in Fe-Fe bond lengths and a marked decrease in coordination number. XANES examination of the Fe K-edge shows a decrease in energy of the main absorption by up to 1 eV, revealing reduction of the Fe3+ components of the biotite by interaction with the He-4(2)2+, the result of low and thermal energy electrons produced by the cascade of electron collisions. Changes in d spacings in the XRD patterns reveal the development of polycrystallinity and new domains of damaged biotite structure with evidence of displaced atoms due to ionization interactions and nuclear collisions. The damage in biotite is considered to have been facilitated by destruction of OH groups by radiolysis and the development of Frenkel pairs causing an increase in the trioctahedral layer distances and contraction within the trioctahedral layers. The large amount of radiation damage close to the monazite can be explained by examining the electronic stopping flux.

Journal Keywords: Radiation Damage Silicates

Subject Areas: Environment, Materials

Instruments: I18-Microfocus Spectroscopy