Native and artificial radiation-induced defects in montmorillonite. An EPR study

S. Sorieul (1) , Thierry Allard (1) , G. Morin (1) , Bruno Boizot (2) , G. Calas (1)

1 LMCP - Laboratoire de minéralogie, cristallographie de Paris
2 LSI - Laboratoire des Solides Irradiés - Irradiated Solids Laboratory

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 g(x) = 2.004 +/- 0.005 g(y) = 2.010 +/- 0.003, g(z) = 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 degrees 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

Mots clés: Montmorillonite, EPR, Radiation-induced defects

Domaines: Autre [cond-mat.other]

S. Sorieul, Thierry Allard, G. Morin, Bruno Boizot, G. Calas. Native and artificial radiation-induced defects in montmorillonite. An EPR study. Physics and Chemistry of Minerals, 2005, 32, pp.1-7. ⟨10.1007/s00269-004-0427-6⟩. ⟨hal-00018081⟩