Small-angle neutron scattering on hydrogen- and deuterium-doped nanocrystalline palladium

The microstructure of a nanocrystalline Pd sample prepared by inert gas condensation was studied by small-angle neutron scattering. To increase information, the contrast of the sample was additionally varied by doping it with H and D (C-H = 3.2 at%, c(D) = 3.5 at%). We modeled the measured intensity by a Pored contribution caused by large heterogenities (pores) and a second contribution caused by a logarithmic normal distribution of spherical grains surrounded by shells of reduced Pd density describing the grain boundaries. This model yields a volume-weighted mean grain radius of 10 nm and a grain boundary thickness of approximately 0.8 nm. The contrast variation due to doping with H and D indicated that H and D were mainly located in grain boundaries. (C) 2000 Elsevier Science B.V. All rights reserved.