Pair Distribution Function studies of nanostructured materials at the high Q resolution powder diffraction beam line at the ESRF

Pair Distribution Function (PDF) analysis method is a powerful tool for the investigation of crystalline or partly crystalline materials, yielding crucial information on the atomic-scale structures of nanosized materials. An increasing number of topics are today tacked by PDF analysis by neutron and X-ray powder diffraction. Nanostructured materials, nanoporous materials, frame-host interaction in zeolites, nano-scale structures (local structures versus average structures) in complex materials for modern applications have been investigated using synchrotron X-ray PDF analysis at the high reciprocal-space (Q) resolution powder diffraction beam line ID31 at the ESRF (France). In this talk I will show some recent results in these areas of research from data collected using hard X-rays at ID31. I will focus on the relation between nanosize structure and superparamagnetism in Ce1-xGdxO2-x/2 compounds. CeO2-based materials (Ce1-xMxO2-x/2; M = Gd, Y, Sm) have been studied in the last years as catalysts, structural and electronic promoters for heterogeneous catalytic reactions and oxide ion conducting electrolytes for electrochemical cells, for which application they show high ion conductivity and would be able to operate at relatively low temperatures (500 - 700°C). Since thermodynamics transport and magnetic properties of nanostructured compounds can be different from those of bulk materials, the local structure of Ce1-xGdxO2-x/2 nanostrucured samples has been investigated by means of PDF analysis (Fig. 1). The local distortions introduced by Gd doping and nanosize in of Ce1-xGdxO2-x/2 samples will be discussed.