Abstract
The structure of such internal interfaces as grain boundaries has an important influence on electronic and mechanical properties. For alpha-alumina, four different symmetrical tilt grain boundaries in alpha-axis orientation were analyzed with the molecular dynamic (MD) simulation technique. The core of a grain boundary usually consists of an open atomic structure with large bonding distances. The size of these pores depends on the tilting angle of the two grains. The largest pore size of more than 0.5 nm was found for the 137-deg Sigma 39 boundary. The crack propagation in an alumina-zirconia composite was calculated by the MD-simulation. The composite showed a much higher fracture toughness than the alumina single crystal in the same orientation. The cubic zirconia particle transforms to an amorphous phase for high stresses at the crack tip. (Author)