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

The external proton beam of the Tandem accelerator of the Research Centre i n Rossendorf/Germany was used to carry out non-destructive particle-induced X-ray emission (PIXE) particle-induced gamma-ray emission (PIGE) and Ruthe rford backscattering (RBS) measurements simultaneously on Art Nouveau artif acts produced around 1900 by Tiffany/USA and Loetz/Austria. These studies s hould proof the technology of producing an iridescent layer on a glass surf ace, By means of the yield ratio Y(Si-K)/Y(Si-gamma) of both characteristic X-radiation (Si-K) and gamma -radiation (Si-gamma) 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 artifacts (about 500 degreesC) with an alco holic solution of SnCl2 [1]. Combined evaluation of the PIXE and RBS spectr a resulted in a thickness of 20-300 nm for this top layer. In addition, a t ransition region between the iridescent layer and the bulk glass was obtain ed by RUMP simulations. Approximately 80% of the total amount of the Sn wer e found to be present in this transition layer and only 10-20% in the outer most surface region. XPS studies showed that the outermost layer consists o f SnO2. The formation of other Sn compounds in the outermost near-surface r egion based on Sn-Si-O during the manufacturing process can be excluded. (C ) 2001 Elsevier Science B.V. All rights reserved.