Influence of Y and La Additions on Grain Growth and the Grain‐Boundary Character Distribution of Alumina

Abstract

Grain‐boundary character distributions (GBCDs) were determined for spark plasma sintered Y‐ and La‐doped aluminas prepared at temperatures between 1450°C and 1600°C. La doping leads to grain boundaries that adopt (0001) orientations 3.7 times more frequently than expected in a random distribution, whereas the Y‐doped microstructures are more equiaxed. At 1500°C, some of the boundaries in the Y‐doped samples transform to a higher mobility complexion; in this microstructure, the grain‐boundary plane is 1.3 times more likely to occur than expected in a random distribution. After the fast‐growing grains impinge, the dominant plane becomes and these boundaries have areas that are 1.2 times more likely to occur than expected in a random distribution. The grain‐boundary planes in the Y‐ and La‐codoped samples preferred (0001) and orientations, combining the characteristics of the singly doped samples. Grain boundaries with a 60° misorientation about [0001] were up to six times more common than random in the Y‐doped samples. The preference for (0001) oriented grain‐boundary planes in the La‐doped sample persisted at all specific misorientations.