Fabrication and Properties of a Pressureless Sintered Silicon Nitride Based on Y2O3 as Sintering Aid

摘要

A powder mixture 91% Si3N4 + 8% Y2O3 + 1% MgO was sintered at 1800 C in nitrogen at atmospheric pressure to a density of 3.25 Mg/cu m. The strength at room temperature was 585 MPa and at 950 C it was 560 MPa. Devitrification of an amorphous phase increased the strength at 1125 C by 44%. The linear shrinkage during sintering was 16%; thus it should be possible to fabricate complex shapes to high dimensional accuracy. The proposed sintering process overcame some of the disadvantages of the reaction-sintering and hot pressing processes. Various mechanical and thermal properties were determined.