Microstructural and Microanalytical Characterization of Pd Clusters in ORMOCER Matrix

Noble-metal clusters dispersed in glass matrix are of great interest for their technological applications such as heterogeneous catalysis, in the realization of non-linear optical devices, in sensor technology, for absorption control in solar reflecting glasses (IROX® coatings) etc.The phys- ical properties of these materials strongly depend on cluster concentration, size distribution and on their structural and chemical nature.High spatial resolution structural and analytical characterization techniques are needed to understand the cluster formation mechanism and the physical properties of these materials.In this work, palladium clusters dispersed in ORMOCER matrix via a modified sol-gel process are structurally and chemically characterized by conventional transmission electron microscopy, high-resolution electron microscopy, electron nanodiffraction and X-ray diffractometry, in order to obtain information on the clusters shape, structure, spatial distribution in the matrix and chemical nature.Samples heat treated both in inert N2 atmosphere and in air at 400 ° C for different times are analyzed in order to obtain a deeper insight in the formation and structural evolution of the clusters and in the oxidation process.In fact after heat treatment in air, clusters oxidation occurs and a PdO shell surrounding a core with different structure ~ 1.5 nm in diameter is formed.Heat treatment in inert N2 atmosphere does not affect the clusters shape, structure and distribution.Microsc.Microanal.Microstruct.6 (1995) Classification