Iridescent Art Nouveau glass - IBA and XPS for the characterisation of thin iridescent layers

The external proton beam of the Tandem accelerator on the research Centre in Rossendorf/Germany was used to carry out non-destructive particle-induced X-ray emission (PIXE) particle-induced gamma-ray emission (PIGE) and Rutherford backscattering (RBS) measurements simultaneously on Art Nouveau artefacts produced around 1900 by Tiffany/USA and Loetz/Austria. These studies should proof the technology of producing an iridescent layer on a glass surface. By means of the yield ratio Y(Si-K)/g(Si-g) of both characteristic X-radiation (Si-K) and g-radiation (Si-g) of the element silicon it could be shown that a thin top layer is present on the glass surface due to the treatment of the heated artefacts (about 500°C) with an alcoholic solution of SnCl2 [1]. Combined evaluation of the PIXE and RBS spectra resulted in a thickness of 20-300 nm for this top layer. In addition, a transition region between the iridescent layer and the bulk glass was obtained by RUMP simulations. XPS studies showed that the outermost layer consists of SnO2. The formation of other Sn compounds in the outermost near-surface region based on Sn-Si-O during the manufacturing process can be excluded.