THE CONTRIBUTION OF LATTICE MATCHING TO THE INTERFACIAL ENERGY BETWEEN DISSIMILAR MATERIALS

Abstract
The interfacial energy of boundaries between dissimilar materials can be described as function of the lattice mismatch, the chemical interaction and the interfacial entropy of the boundaries. Based on experiments involving a sphere-rotation method and undercooling measurements of (solid/liquid) phase mixtures in a droplet dispersion, an attempt is made to separate the influence of the different contributions. The atomic structure of interphase boundaries between noble metals and ionic crystals can be described by the "lock-in" model : low energy interphase boundaries were found if close packed rows of atoms at the "surface" of the metal crystal lock into the "valleys" between close packed rows of atoms at the "surface" of the ionic crystal. At higher temperatures the relative stability of different interphase boundary structures may change depending on the degree of axial commensuration and the related interfacial entropies. Hence, the contribution of lattice matching to the interfacial energy can decrease or vanish completely in some cases, resulting in a commensurate/incommensurate phase transition (e.g. for Au/Al₂O₃). Furthermore, the droplet undercooling experiments demonstrate that good matching between two crystal lattices (substrate/nucleus) can favour formation of metastable phases due to the lowering of the activation barrier for nucleation during crystallization from a highly undercooled liquid.