TEM characterization of palladium and silver nanoclusters in glass matrix

Palladium and silver nanoclusters doped silica gels and coatings were prepared by the sol-gel process and characterized by conventional transmission electron microscopy, high resolution electron microscopy and x-ray diffractometry. The Pd/Si and Ag/Si atomic ratios were 0.01 and 0.12, respectively. The Pd nanoclusters are very homogeneously distributed in the matrix on a micron scale having a very narrow size distribution with an average value of (4.5+/-0.5) nm. Ag clusters show a relatively broad size distribution. The average diameter distribution obtained from the analysis of several bright field images from a coating heat-treated at 550 degrees C exhibits two clear modes around 3.5 mn and 19 nm, respectively. The concentration of larger clusters is, however, very small in comparison to the smaller ones. Heat treatments were performed on both Pd and Ag samples, in order to have a deeper understanding of the clusters' structural evolution. No noticeable variations in the cluster diameter distribution are observed in the Pd samples after the heat treatment. The formation and growth of the Ag clusters depend significantly on the temperature and heat treatment time