BIMETALLIC PDCU AND PDCU3 PARTICLES PREPARED BY WET IMPREGNATION-HRTEM - STUDY OF THE STRUCTURE AND THE INTERFACE WITH THE MGO SUBSTRATE

Bimetallic particles of PdCu and PdCu3 are prepared by decomposition o f organometallic compounds on MgO micro-cubes. During the annealing be tween 350 and 400 degrees C, in reducing atmosphere, PdCu particles gr ow with the fee structure, without defined shape. The particles epitax ially (001) oriented on MgO are dilated and accommodated to the substr ate. After annealing at 450 degrees C, the particles adopt the beta or dered structure. The particles are limited at the edges by (100) and ( 110) faces. Most of them are oriented (001) on MgO with [110]PdCu para llel to [100]MgO, which corresponds to a perfect accommodation of the lattices without deformation compared to the bulk, despite of the redu ction in H-2. The PdCu3 particles smaller than about 10 nm were found with the alpha ordered structure, without periodic anti-phase boundari es.