article posted 23 June 2016
georges Calas FSGT is Chair of Mineralogy at the University Institute of France and a professor at the Pierre & Marie Curie University in Paris.
He was the 2014–2015 Chair in “Sustainable Development – Environment, Energy, and Society” at the Collège de France in Paris. His research, based on solid-state
spectroscopic and diffraction methods and numerical modeling, 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, encompassing a
broad range of applications in environmental mineralogy and materials sciences, including cultural heritage, functional glasses and glass nuclear waste forms. A member
of Academia Europaea and a Foreign Fellow of the Royal Society of Canada, he is a fellow of the Society of Glass Technology, the Mineralogical Society of America and
the Geochemical Society.
Transition Elements and Glass Coloration.
Georges Calas*, Laurence Galoisy, Laurent Cormier, Gérald Lelong, Myrtille Hunault and Natan Capobianco
Institute of Mineralogy, Physics of Materials and Cosmochemistry, Pierre & Marie Curie University and CNRS, Paris, France
Since the discovery of glass making, the coloration caused by transition elements, either brought by impure raw materials or intentionally developed, has always
been one of the most attractive properties of glasses. This probably culminated during the middle age with the intense use of colored glasses. Still now, many glassy
products take advantage of glass coloration, including containers and tableware, art and design or functional glasses. Transition metal ions constitute the most important
source of glass coloring agents. Coloration varies, for a given transition element, as a function of chemical and physical parameters such as glass composition or
melting/fining conditions. At the same time, the electronic transitions responsible for light selective absorption and glass coloration provide unique information
about the local structure and chemical bonding of glasses. This presentation aims to review optical absorption data at the light of complementary information provided
by a broad range of experimental and numerical and as 5-fold coordination, distribution of site geometry, sensitivity to the chemical bond, medium-range organization,
heterogeneous spatial distribution… Some of these structural characteristics are inherited from the peculiar dynamics of silicate melts and may show a significant
modification as a function of temperature. As transition elements can be connected to the various structural subsets of glasses, they are useful color indicators
of the complex structure of these materials. Vice versa, using a better knowledge of the structural behavior of transition elements, the variation of colors may be
rationalized as a function of glass composition and melting conditions.