Seeding procedure and transient processes at crystallization of the Ce-doped Al ₂ O ₃ -YAG eutectic by the HDS method using sapphire seed

Abstract The results of a special seeding procedure for growing a cerium-doped Al 2 O 3 -YAG eutectic composite using a sapphire seed with the crystallographic maxis coinciding with the growth direction are presented. The microstructure and crystallographic texture of a sample cut longitudinally in the direction of crystallization were studied using scanning electron microscopy, energy-dispersive X-ray spectroscopy, and electron backscattering diffraction methods. The crystallization of the region with a fine eutectic structure was found to be accompanied by the segregation of Al 2 O 3 , leading to the formation of large inclusions of the sapphire primary phase and a change in the orientation of the crystallographic m-axis of sapphire lamellae located near the boundary of the transition to a coarser eutectic structure. However, beyond the boundary, the coarse Al 2 O 3 lamellae returned to the crystallographic orientation of the sapphire seed, suggesting a possible orientation inheritance.