Thespecimenswerepreparedbymoldingthemixtureofsilicafume(w(SiO2)=94.5%;averageparticlesize:0.08μm)andsiliconnitride(≤0.074mm)withamassratioof11,carbonembeddedfiringat1300℃,1450℃,1500℃,1550℃and1600℃for3hinair,andthenwater-cooling,respectively.Themicrostructureandphasecompositionofthespecimenswereanalyzed.Theresultsshowthat:(1)silicafumereactsobviouslywithSi3N4formingSi2N2Oabove1550℃.TheedgesandcornersofSi3N4grainsbecomesmoothandtheSi3N4grainsdistributeinthecontinuouscementationphaseofSi2N2OformingthedensestructureofSi2N2OpackedSi3N4;(2)below1500℃,theedgesandcornersofSi3N4grainsareclear,Si2N2Odoesn'tform,andonlySiO2crystallizesfromsilicafumewhichhappensobviouslyat1300℃.
