The U-phase in heat-treated sialon ceramics

Carrying out the heat-treatment step on sialon ceramics at different temperatures yields different crystalline phases. A new phase, designated "U", which has been observed in sialon compositions heat-treated at 1000-1350 deg C, is described. The results show that U-phase is an alternative secondary crystalline phase in beta ' sialon ceramics, but it is unlikely to be of commercial interest because of its poor thermal stability. However, it provides another member of the steadily increasing number of phases which occur by devitrification of nitrogen glasses at the lower end of the temperature range. 4 ref.--A.R.