Microstructural and Microanalytical Characterization of Pd Clusters in ORMOCER Matrix

Abstract. 2 0 1 4 Noble-metal clusters dispersed in glass matrix are of great interest for their technolog- ical applications such as heterogeneous catalysis, in the realization of non-linear optical devices, in sensortechnology,forabsorptioncontrolinsolarreflectingglasses(IROX®coatings)etc. Thephys- icalpropertiesofthesematerialsstronglydependon clusterconcentration,sizedistributionandon theirstructuralandchemicalnature. Highspatialresolutionstructuralandanalyticalcharacterization 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, inordertoobtaininformationon theclustersshape,structure,spatialdistributioninthematrixand 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 n m in diameter is formed. Heat treatment in inert N2 atmosphere does not affect the clusters shape, structure and distribution.