EXTENDED X-RAY ABSORPTION FINE-STRUCTURE STUDIES ON CO-DOPED NANOCRYSTALLINE CU

Nanocrystalline materials are single-phase or multiple-phase polycrystals with a crystallite size in the range of a few nanometres (typically 5-20 nm), so that about 30 vol.% of the material consists of grain or interphase boundaries. Previous extended X-ray absorption fine-structure (EXAFS) studies have indicated an atomic arrangement in this grain-boundary component exhibiting a broad distribution of interatomic spacings which differs from the atomic structure of the crystalline or glassy state. Doping of the grain-boundary component of nanocrystalline Cu with Co atoms and subsequent EXAFS studies on the Co absorption edge yields information about the local atomic arrangement of the probe atoms in the grain boundaries. The results suggest that Co atoms substitute for Cu atoms both in the grain boundaries and in the lattice of the Cu crystallites and/or form Co precipitates.