窒化ケイ素の長時間酸化により生成したトリジマイトのEPMAによる観察

概要

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Hot-pressed silicon nitride specimens were oxidized in air flow at 1200℃ for up to 3000 h. Tridymite was detected by X-ray diffraction after 750 h oxidation, and the crystals of 3-4 X 200-300 μm were observed by composition image on the 3000 h-oxidized layer. The composition change in the phases by oxidation were examined with an EDS. The relative amount of SiO_2 in the Y2S phase decreased during oxidation leading to the stoichiometric composition (Y_2O_3・2 SiO_2 ). The glassy phase formed after 3000 h oxidation contained several metallic oxides such as Y_2O_3, CaO, MgO, Na_2O, K_2O and 10 wt% Al_2O_3. Incorporation of alkali and other metallic oxides into the glassy phase lowered the melting temperature of the silica (cristobalite)-rich phase. The glassy phase acted as a flux of silica to promote the crystallization of tridmite.
社団法人日本セラミックス協会の論文
1988-06-01