Effect of ion implantation on fracture stress of Al 2O 3

Abstract

Effects of ion implantation and subsequent thermal annealing on the fracture stress of single-crystalline α-Al 2O 3 have been investigated for 400 keV N and 300 keV Ni ions. Upon N or Ni implantation, the flexural strength of a specimen 7 × 25 × 1 mm 3 in size increased by 20 to 60% in the ion dose range from 1 × 10 15 to 1 × 10 17 ions cm 2 . By post-implantation thermal annealing, the relative flexural strength for the N implanted specimen recovered gradually with annealing temperature followed by a complete recovery at around 1300°C. This behavior of recovery for flexural strength has been found to be similar to that for radiation damage. On the other hand no recovery of flexural strength has been observed for the Ni implanted specimen, in which a spinel compound NiAl 2O 4 formed upon thermal annealing at temperatures above 1000°C. In N implantation, the strengthening results entirely from the effect of radiation damage, whereas in Ni implantation the formation of a surface NiAl 2O 4 layer with post-implantation thermal annealing is also effective in the strengthening.