Aggregates of small silver particles in surface layers of glasses — electron microscopy and optical microspectroscopy

In glasses containing antimony or arsenic in the order of 1 weight-% the treatment with a silver-containing paste yields a dark-red surface layer. Transmission electron microscopy shows that there are aggregates of spherical silver particles in the coloured layer. Optical microspectroscopy proves extinction spectra consisting of two bands. Comparing these spectra with calculated ones reveals that the two bands can be explained by the existence of aggregates. The change of the extinction within the coloured layer is a result of the mutually different spatial arrangements of the silver particles which were found by electron microscopy.