METAL-CERAMIC INTERFACES IN INTERNALLY REDUCED (MG,CU)O

Conventional and high resolution TEM observations of the precipitation scale obtained after internal reduction of (Mg,Cu)O single crystals have revealed special orientation relationships between the metal copper and the ceramic matrix MgO. The intermediate valence state of copper induces a mechanism in two steps for this internal reduction. In the first one, cuprite Cu2O forms in one of the four orientations (T, TA, D, DA); in the second step, while the reaction front penetrates further into the matrix, cuprite particles are reduced to metallic copper. The orientation of the particles within the matrix can either be maintained OT evolve into a twinned orientation.