Orientations and seed type effect on Al2O3-YAG-ZrO2 eutectic microstructure solidified from the melt by the micro-pulling down technique

摘要

Al2O3-YAG-ZrO2 eutectic ceramic rods of 5 mm in diameter were grown by micro-pulling down technique. The seeding and the solidification rate affect microstructure, morphology, crystallography, and thermal stress of the solidified ceramics. The ternary eutectic grown through zirconia (111) seed had inhomogeneous and irregular cellular microstructures. At the stationary stable regime, the microstructure spacing (lambda) depends on the pulling rate (v). Under solidification rate of 0.5 mm.min- 1, the rods grown by using eutectic poly-crystal, (100), (111) YAG, and c(0001), A(1-210), M(10-10) sapphire seeds, the YAG and ZrO2 phases are oriented along the 100 direction parallel to the growth direction. The zirconia (111) seeding X-ray diagram eutectic presents additional peaks and the monoclinic ZrO2 phase appears at the solidification rate of 1 mm.min-1. The rods grown through ZrO2 seeding are more stressed than those solidified by using eutectic, YAG and sapphire seeds, respectively.