Orientation relationships of unidirectionally aligned GdAlO3/Al2O3 eutectic fibers

Unidirectionally solidified rare-earth activated GdAlO3(GAP)/Al2O3 eutectic crystal with well-aligned fibrous structure exhibits excellent light guiding property and can be used as a scintillator plate for high-resolution X-ray imaging. In this paper, the microstructures and orientation relationships of the GAP/Al2O3 eutectic fibers were investigated. The regular GAP single crystal fibers with a hexagonally close-packed arrangement grew straight in the same direction along the solidification direction, and were embedded in a c-axis oriented Al2O3 single crystal matrix. The majority of GAP fibers had the orientation relationships of [0 1 0]GAP//[0 0 0 1]Al2O3 to the growth direction and (1 0 0)GAP//(1 1 2¯ 0)Al2O3 to the interface plane, while slight misorientation angle of both [0 1 0]GAP axis and (1 0 0)GAP plane were observed. In the GAP/Al2O3 interface boundary, the lattice misfit between the two phases was relieved by insertion of extra half-planes on the Al2O3 side.