Improved densification by nano-sized sintering aids for Si3N4

The densification of Si3N4 with nano-sized sintering aids that were in situ incorporated by a combustion process was studied in comparison with that o f sintering aids mixed by ball milling. The combustion process directly pro duces amorphous and nano-sized Y-Al oxides within the Si3N4 powder. X-ray d iffraction results indicate that amorphous Y-Al oxides begin to crystallize into Y3Al5O12 at about 600 degrees C. Additionally the nano-sized sinterin g aids are more homogeneously distributed and thereby promote the formation of eutectic melts at lower temperatures during liquid-phase sintering. The refore, the densification process of Si3N4 during liquid-phase sintering is strongly accelerated. The microstructure of as-sintered parts from combust ed powder seems more dense and homogeneous.