Influence of <scp> <scp>Y</scp> </scp> and <scp> <scp>La</scp> </scp> Additions on Grain Growth and the Grain‐Boundary Character Distribution of Alumina

Abstract

Grain‐boundary character distributions ( GBCD s) 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.