Atomic structures and properties of systematic 0001 tilt grain boundaries in alumina

摘要

Several kinds of alumina bicrystals were systematically fabricated by joining two single crystals at high temperature. The alumina bicrystals have the [0001] symmetrical tilt grain boundaries which include low sigma boundaries (Σ3, Σ7), high sigma boundaries (Σ19 etc.), small angle boundaries and high angle boundaries. Grain boundary structures were mainly observed by high-resolution electron microscopy (HREM). It was found that the grain boundary with incoherent atomic structure took high energy and the boundary with coherent atomic structure took low energy. The structure of 32.0° incoherent tilt boundary is disordered, and took high energy of about 0.6J/m~2. The atomic structure of the Σ3 boundary was completely coherent as well as Σ1 grain boundary. This boundary took extremely low energy of about 0.05J/m~2. The 2.0° tilt boundary was consisted of an array of periodic dislocations. This boundary with coherent and incoherent atomic structure takes the middle energy of about 0.3J/m~2.