Pore morphology designs of porous Si3N4-based ceramics using Si3N4 and Al2O3 poly-hollow microspheres as pore-forming agents

• Si3N4 and Al2O3 poly-hollow microspheres (PHMs) were used as pore-forming agents.
• Porous Si3N4-based ceramics with Si3N4 and Al2O3 PHMs have different microstructures.
• Si3N4 and Al2O3 PHMs play different roles in affecting mechanical properties.

Porous Si3N4-based ceramics with different pore morphologies were prepared choosing Si3N4 and Al2O3 poly-hollow microspheres (PHMs) as pore-forming agents. The phase compositions, morphologies and mechanical properties of the samples were investigated. The SEM results show that the intact Si3N4 and Al2O3 PHMs distribute uniformly in the green body. However, after the sintering process, the basal body of the samples with Si3N4 PHMs is fibrous and Si3N4 PHMs still exist, while the basal body of the samples with Al2O3 PHMs is dense and Al2O3 PHMs disappear. In addition, the samples with Si3N4 and Al2O3 PHMs have different mechanical properties due to their different microstructures.