PREPARATION OF MULTICATION ALPHA-SIALON CONTAINING STRONTIUM

The possibility of having Sr as an interstitial metal cation in alpha- SiAlON has been investigated in two systems: a single-cation system (S i3N4-SrO-AlN) and a multication system (Si3N4-(Y2O3/SrO/CaO)-AlN). It was found that Sr alone does not form alpha-SiAlON and that Sr could o nly be accommodated in alpha-SiAlON in conjunction with Y and Ca. The Sr content of alpha-SiAlON increased as the total content of (Y + Ca) increased and appeared to reach a limit at 0.5 at.%, or 0.15 atom per alpha-SiAlON. Unexpectedly, some of the alpha-SiAlON that contained (S r + Y + Ca) was present as laths or fibers with the c-axis perpendicul ar to the hot-press direction.