Glass - Back to the Future!

Presenting Author:
Gérald Lelong

article posted 27 April 2016

Gérald Lelong studied chemical physics at Bordeaux University and made a Ph. D in Physics of glassy liquids in 2007. After a Post-doctoral position at Cornell University (NY, USA), he joined in 2008 the Institute of Mineralogy and Physics of Matter and Cosmochemistry (IMPMC) in the research team (Glass and Minerals) in Paris. He completed his habilitation in 2015. His main research areas are related to the understanding of glass structure in glasses and melts placed under extreme conditions (high-pressure / high-temperature) by following the local environment of low-Z elements.

Optical and X-ray absorption spectroscopies of iron in minerals and glasses: experiment and theory

Gérald Lelong*,1, Vincent Vercamer1,2, Hiroyuki Hijiya2, Amélie Juhin1, Georges Calas1, Laurence Galoisy1, Christian Brouder1, Marianne Arrio1
1 Institut de Minéralogie, Physique des Matériaux et Cosmochimie (IMPMC), UPMC, CNRS-UMR 7590, Paris, France
2 Research Center AGC, Yokohama, Japan
3 ESRF, Grenoble, France

As iron is the most abundant transition element, understanding the crystal chemistry of Fe2+ and Fe3+ in minerals and glasses remains an important issue. A direct approach may be to investigate the spectroscopic properties of both oxidation states of iron, by quantifying the influence of Fe-site geometry and by constraining different experimental spectroscopic data by simulations. We will present an extensive set of data on the spectroscopic properties of 12 Fe2+ and Fe3+ minerals, using two kinds of techniques: synchrotron-based high-resolution X-ray spectroscopy (Resonant Inelastic X-ray Scattering (RIXS), X-ray Absorption Spectroscopy with High Energy Resolution Fluorescence Detection (HERFD) and optical absorption spectroscopy. The reference compounds investigated contain Fe2+ and Fe3+ in 4-, 5- and 6-coordination and various site geometries: gillespite ([4]Fe2+), staurolite ([4]Fe2+), grandidierite ([5]Fe2+), siderite ([6]Fe2+), hypersthene ([6]Fe2+), rodolicoite ([4]Fe3+), ferriorthoclase ([4]Fe3+), yoderite ([5]Fe3+), grattarolaite ([5]Fe3+), andradite ([6]Fe3+), acmite ([6]Fe3+) and hematite ([6]Fe3+). Experimental data are well reproduced by Ligand Field Multiplet (LFM) calculations, which enables to relate the spectroscopic properties to the local crystal field. This sheds light on the chemical, geometrical and ligand field dependence of the spectroscopic behavior of iron. The set of parameters obtained will be used to discuss the surrounding of Fe2+ and Fe3+ in glasses.