Phase equilibrium studies in Si 2N 2O-containing systems: I. phase relations in the Si 2N 2OAl 2O 3Y 2O 3 system

Abstract

Sub-solidus phase relations have been studied in the Si 3N 3OAl 2O 3Y 2O 3 system. The results show that Si 2N 2O forms a small range of compositions with Al 2O 3 (O'ss) containing up to 15 m/o Al 2O 3, and that 2Y 2O 3·Si 2N 2O forms a continous solid solution series with 2Y 2O 3·Al 2O 3 (J ss). In the Si 2N 2O-rich corner of the system, Si 2N 2O reacts with Y 2O 3 at 1550°C to form Si 3N 4 and Y 10 (SiO 4) 6N 2(H-phase). Four quarternary phase regions occur in this system: HSi 3N 4Y 2O 3·Si 2N 2O3Y 2O 3·5Al 2O 3 HSi 3N 43Y 2O 3·5Al 2O 3-O′ss HSi 3N 4O′ ssSi 2N 2O HY 2O 3·Si 2N 2O3Y 2O 3·5Al 2O 34Y 2O 3·Si 2N 2O·Al 2O 3 From the results of this work, the sub-solidus phase diagram and the isothermal section at 1550°C in the Si 2N 2OAl 2O 3Al 2O 3 system are presented. A large liquid-phase area near the Si 2N 2OAl 2O 3 side that may effect the sintering of O′-sialon ceramics is reported. The difference between our results and those previously reported in the Si 3N 4SiO 2Y 2O 3 phase diagram is also discussed.