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Low-magnesium uranium-calcite with high degree of crystallinity and gigantic luminescence emission

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Valle Fuentes, Francisco José and García Guinea, Javier and Cremades Rodríguez, Ana Isabel and Correcher Delgado, Virgilio and Sánchez Moral, Sergio and Gon´zalez Martin, Rafael and Sánchez Muñoz, Luis and López Arce, Paula (2007) Low-magnesium uranium-calcite with high degree of crystallinity and gigantic luminescence emission. Applied Radiation and Isotopes, 65 (1). pp. 147-154. ISSN 0969-8043

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Official URL: http://www.sciencedirect.com/science/article/pii/S0969804306002983


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Abstract

Cabrera (Madrid) low-Mg calcites exhibit: (i) an unusual twofold elevation in X-ray diffraction pattern intensity; (ii) a 60-fold elevation of luminescence emission, compared to six common natural calcites selected for comparison purposes; (iii) a natural relatively high radiation level of circa 200 nSv h^-1 not detected in 1300 other calcites from the Natural History Museum of Madrid. Calcites were analysed by the X-ray diffraction powder method (XRD), cathodo-luminescence spectroscopy in scanning electron microscopy (CL-SEM), thermoluminescence (TL), differential thermal analysis (DTA), X-ray fluorescence spectrometry (XRF) and particle size distribution (PSD). The Cabrera calcite study shows: (i) helicoidally distributed steps along the (0001) orientation; (ii) protuberance defects onto the (0001) surface, observed by SEM; (iii) XRF chemical contents of 0.03% MgO, 0.013% of Y_2O_3, and 0.022% of U_3O_8, with accessory amounts of rare earth elements (REE); (iv) DTA dissociation temperature of 879 degrees C; (v) TL maxima peaks at 233 and 297 degrees C whose areas are 60 times compared to other calcites; (vi) spectra CL-SEM bands at 2.0 and 3.4 eV in the classic structure of Mn^2+ activators; (vii) a twofold XRD pattern explained given that sample is a low-Mg calcite. The huge TL and CL emissions of the Cabrera calcite sample must be linked with the uranyl group presence. This intense XRD pattern in low-Mg calcites could bring into being analytical errors.


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© 2006 Elsevier Ltd. All rights reserved.
The experiment was supported by the C.I.C.Y.T. CGL2004-03564/BTE, Communidad de Madrid, MATERNAS-S-0505/MAT/000094 and BFM2002-00048 Projects. Thanks are also due to Martin Fernandez (Colmenar Viejo, Madrid) for the valuable help in the Cabrera granite quarries for providing the calcite samples. The authors thank R. Schmidtling of the Museum Research Laboratory of the Getty Conservation Institute for the critical review of the manuscript.

Uncontrolled Keywords:X-Ray-Diffraction, Quantitative-Determination, Retrospective Dosimetry, Xrd Analysis, Quartz; Minerals, Thermoluminescence, Interface, Xafs
Subjects:Sciences > Physics > Materials
ID Code:23102
Deposited On:15 Oct 2013 11:51
Last Modified:09 May 2016 14:30

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