400℃までの温度におけるSiO_2-AlPO_4系の相平衡の検討

概要

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The phase relationships along binary join of SiO_2-AlPO_4 were investigated up to 400℃ using several starting materials made by a partial solution route. Precursors used were boehmite (AlOOH), H_3PO_4, non crystalline silica (Ludox, Cab-O-Sil) , and quartz. Studies up to 400℃ showed that SiO_2, AlPO_4, and its hydrate were the only crystalline and non-crystalline phases present along the binary join, and no substantial crystalline solution of any ternary phase was observed. Three polymorphic forms of AlPO_4, namely, berlinite, tridymite form, and cristobalite form, coexisted at as low as 200℃. The nature of the silica precursors greatly influenced the development of the polymorphic phases of AlPO_4 .The low quartz precursor suppressed the formation of the cristobalite form of AlPO_4 and favored berlinite production. On the other hand, non crystalline silica with a cristobalite-like broad XRD peak suppressed the formation of berlinite and enhanced that of the cristobalite form of AlPO_4. The silica precursors acted as structural seeds for the growth of AlPO_4. These precursor effects indicate that heteroepitaxy is very significant during the nucleation and growth of AlPO_4 phases on the surface of SiO_2 particles even in these low temperature reactions. The influence of other precursors and route during the syntheses of AlPO_4 and other phases in the SiO_2- AlPO_4 are discussed.
社団法人日本セラミックス協会の論文
1990-02-01