Interpretation of Alumina/Yttrium-Aluminum Garnet Orientation Relationships by Geometric Criteria

ABSTRACTGeometric criteria for low interface energy and interface structure were tested for the cubic-rhombohedral system YAG/alumina. Orientation relationships near (111){110}a // (112){110}y and facets on (111)a(112)y were observed in both sol-gel derived composites and directionally solidified eutectic composites. The ΣYAG=12 near-CSL of 2{111}, {110}, {112} was inferred to be the preferred structural unit. Dislocations with b=1/3{111}a and b=1/2{110}a were observed and inferred to accomodate deviation from the structural unit, respectively. The {110}a,y direction met some of the criteria for an invariant line. Although the OR was explained by geometric criteria it would have been difficult to predict it with such criteria