Crystallite Size Controls the Crystal Structure of Cu_(60)Pd_(40) Nanoparticles

摘要

Structurally disordered (Cu type of structure) or ordered (CsCl type of structure) modifications of intermetallic Cu_(60)Pd_(40) nanoparticles can be synthesized by co-reduction of Cu- and Pd-acetylace-tonate using LiBEt_3H in THF or annealing in tetradecane, respectively. It is shown by X-ray diffraction, transmission electron microscopy, selected area electron diffraction, differential centrifugal sedimentation, and thermal analysis that the formation of the ordered or the disordered modification depends on the crystallite size of the nanoparticles rather than on temperature. Crystallites smaller than ~20 nm form the disordered modification of Cu_(60)Pd_(40), whereas crystallites larger than 20 nm prefer the ordered modification.