The Science & Technology
of Glass
Cambridge - Monday 4th to
Wednesday 6th September 2017

Georges Calas

article posted 22 May 2017

Georges Calas FSGT is University Institute of France Chair of Mineralogy at the Pierre & Marie Curie University in Paris. His research centers on structural properties of materials linked to the presence of minor components and impurities or radiation-induced defects. This helps rationalize how the molecular-scale organization of minerals, glasses, and melts controls their properties, with applications in environmental and materials sciences, including cultural heritage, functional glasses and nuclear waste materials.

#Structural control of the coloration of alkali borate glasses by 3d-elements
Georges Calas*, Natan Capobianco, Laurent Cormier, Laurence Galoisy, Myrtille Hunault, Gérald Lelong

Institute of Mineralogy, Physics of Materials and Cosmochemistry, Université P&M Curie, Paris, France.

The presence of transition elements in alkali borate glasses is at the origin of one of the most noticeable chemical dependence of the color of oxide glasses. We present a set of high-quality optical absorption spectra of borate glasses containing Cr , Co , Ni and Cu . It is noteworthy that the variations in glass composition cause different modifications in the speciation of the transition elements in these glasses: crystal-field variations, site distribution or distortion of the site geometry. Such differences depend on the existence of either only one or more sites occupied by the transition element. These spectroscopic properties will be discussed at the light of recent findings on the medium-range organization in borate glasses, in particular B coordination and the geometry of super-units. The local rigidity induced by these latter also explains the formation of ordered element clusters, already demonstrated by EXAFS and XANES in low-alkali borate glasses containing Ni, Co or Zn.