Effect of Various Additives and Method of Sintering on the Silicon Nitride Phase Transformation

The main tendencies of the influence of the most popular oxide additives on β-silicon nitride content of such methods as sintering without pressure and spark plasma sintering were considered. The maximum amount of β- silicon nitride was found in the short time pressureless sintered material with magnesium and aluminum oxide. With an increase in the spark plasma sintering temperature from 1550° C to 1650° C an increase in the density of both materials with Al
₂
O
₃
- Y
₂
O
₃
and Al
₂
O
₃
-MgO was observed. Using of yttrium oxide assisted the intensification of the phase transformation much more than the addition of magnesium oxide according to the XRD results. In particular, the amount of β-silicon nitride varies from 18 % up to 83 % with an increase in temperature of spark plasma sintering from 1550° C to 1650° C for Al
₂
O
₃
-Y
₂
O
₃
doped silicon nitride whereas the amount of β-silicon nitride for Al
₂
O
₃
-MgO doped silicon nitride varies insignificantly from 11 % up to 15%. Such physical property as density was also discussed.