Native and artificial radiation-induced defects in montmorillonite. An EPR study |
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| Authors: | S Sorieul T Allard G Morin B Boizot G Calas |
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| Institution: | (1) Laboratoire de Minéralogie Cristallographie de Paris, UMR CNRS 7590, Universités Paris 6 et 7, IPGP, T 16–26, 2ème Étage, case 115, 4 Place Jussieu, 75252 Paris cedex 05, France;(2) CEA/DSM/DRECAM /Laboratoire des Solides Irradiés, École Polytechnique, 91128 Palaiseau CEDEX, France |
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| Abstract: | A natural montmorillonite containing radiation-induced defects was studied with Electron Paramagnetic Resonance (EPR) spectroscopy (X- and Q-band). A first dominant native defect, namely native defect 1, is identified. It gives rise to an orthorhombic spectrum with gx= 2.004 ± 0.005 gy= 2.010 ± 0.003, gz= 2.065 ± 0.002. Simulation of the EPR spectrum at X- and Q-band reveals a second native defect with isotropic spectrum at g= 2.019 ± 0.005. Both are electron holes trapped on oxygen atoms of the structure. The native defect 1 is located on an oxygen-silicon bond or a non-bonding orbital parallel to the c* axis. These defects are annealed at 500°C and the half-life determined for native defect 1 is circa 3,000 years. Irradiations with beta rays produced two additional hole centers of lower stability and distinct EPR parameters. Artificial irradiations show that montmorillonite can be used as a dosimeter in a large dose range. |
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| Keywords: | Montmorillonite EPR Radiation-induced defects |
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