Lock-in structures obtained in [formula omitted] and [formula omitted] interfaces at elevated temperatures

Abstract

Measurements of the low energy orientation relationships between Au and MgO single crystals at 550, 750 and 900°C indicate a variation of the boundary energy with temperature. Over the whole temperature range studied the boundaries are ordered and can be described according to the lock-in model: low energy orientation relationships are obtained if a large number of close packed rows of atoms at the “surface” of the metal crystal locks-in the “valleys” between close packed rows of ions at the “surface” of the ionic crystal. A phase diagram of Au MgO interfaces is developed and exhibits highest thermal stability for interphase boundaries with close packed atomic structures. In addition, the validity of the lock-in model is checked by comparison with experimental data for the interfacial energy between Ag and NaCl crystals. Whereas the coincidence concept fails to describe low energy conditions for interphase boundaries between noble metals and ionic crystals accurately, it is demonstrated that the “lock-in model” is suitable to describe the structure/energy dependence of this type of interfaces. Low energy interfacial structures can be described by two-dimensional short period units of close packed directions matching at the boundary between both crystals.