Paul A. Bingham3, Laurence Galoisy*1, Georges Calas1, Myrtille Hunault2, Prince Rautiyal3 1Sorbonne Université, Institut de Minéralogie de Physique des Matériaux et Cosmochimie, Paris France 2SOLEIL Synchrotron, l’Orme des merisiers Saint-Aubin, Gif-Sur-Yvette, France 3Materials and Engineering Research Institute, Faculty of Arts, Computing,Engineering and SciencesScience, Technology and Arts, Sheffield Hallam University, Sheffield, UK
Uranium has been used as a coloring agent in glasses for decoration, dishes and glassware and other functional objects for about one century. It was particularly popular during the “Art Nouveau” and “Art Déco” periods in Europe, USA, and Japan. However, restrictions were placed on the use of uranium in 1942 and it soon disappeared from workshops.
The goal of this study is to investigate the speciation of uranium in these glasses, i.e. the oxidation state and the spectroscopic properties of uranium. The other interest was placed on searching for evidence of radiation damage suffered by the glass over many decades, due to the presence of this element. Whereas much work has been done on radioactive glasses of technological interest for storage of nuclear wastes, little has been reported on these decorative objects.
U speciation and radiation damage have been investigated in two U containing historical pieces: a 1920’s-1930’s Art Deco green glass, manufactured by Bagley’s in the NorthEast of England, and a 1940 yellow « vaseline uranium glass » vase manufactured by Thomas Webb in Stourbridge. Both glasses glow very strongly under UV light. They do not require special handling due to the low radiation levels (US Nuclear Regulatory Commission, 2001). The radiation damage was investigated by Electron Paramagnetic Resonance (EPR) and U speciation was investigated by UV-visible-near infrared spectroscopy and X-ray Absorption Near-Edge Structure (XANES). The glass composition and homogeneity were analyzed by electron microprobe.
EPR show similar spectra before and after a thermal treatment at 440°C during 24 hours. This indicates that the investigated glasses do not show evidence of paramagnetic radiation-induced defects due to the presence of U. This also indicates that the radiation dose suffered by the glass was not high enough to create these defects. However, the presence of multivalent elements present as impurities, as Fe, Mn and U, may provide possible traps for electrons and positive holes created by the sample radioactivity. Optical absorption and U high-resolution M4-edge XANES reveals that uranium appears mostly present as hexavalent and impurities of reduced species with a distribution of U-sites, which do not correspond to typical uranyl groups, by contrast to those observed in alkali-poor borate glasses (Hunault et al, this meeting), but rather indicate a smaller number of equatorial oxygens. These very first data obtained on uranium in silicate glasses suggest that this element is present in at least two different local coordination environments. This distribution will be discussed in relation to the presence of nanoscale structuring of these complex soda-lime glasses. These U(VI) species are responsible for the yellow color of the Webb glass. However, the typical green color of the Bagley’s glass is not related to the presence of U4+, but rather to that of Cu2+, shown by both optical and EPR spectroscopies.