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

Grain-boundary character distributions (GBCDs) were determined for spark plasma sintered Yand 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 f0112g grain-boundary plane is 1.3 times more likely to occur than expected in a random distribution. After the fastgrowing grains impinge, the dominant plane becomes f1120g and these boundaries have areas that are 1.2 times more likely to occur than expected in a random distribution. The grainboundary planes in the Yand La-codoped samples preferred (0001) and f0112g 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.