Abstract
Using Yb2O3 or Y2O3 as s single sintering additive, the porous Si3N4 ceramics with excellent mechanical properties were successfully fabricated by pressureless sintering. The influence of Y2O3 and Yb2O3 on the microstructure and mechanical properties of porous Si3N4 ceramics was investigated. The results show that both sintering additives can effectively promote α to β phase transformation, and microstructures with elongated β-Si3N4 grains interlocking and superimposing on each other can be obtained. However, sinterability, phase transformation and mechanical properties of the porous Si3N4 ceramics with Yb2O3 were more excellent than the ceramics with Y2O3. The specimens with Yb2O3 had high aspect ratio β-Si3N4 grains, and formed the high melting crystalline Yb4Si2N2O7.
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