金属アルコキシドから合成したβ、β"アルミナ前駆体の結晶化過程

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β, β"-Alumina precursors were prepared under the various synthetic conditions using aluminum isopropoxide and sodium ethoxide. Crystallization of these precursors with heating was examined by differential thermal analysis, powder X-ray diffraction and infrared absorption analyses. Two types of crystallization processes were observed for these precursors, which were controlled by the amount of acetic acid added in the precursor synthesis. At a low molar ratio of acetic acid/aluminum isopropoxide (Ac/Al=0.35), γ-alumina type phase with broad peaks in X-ray diffraction pattern was formed as a primary crystalline phase. On the other hand, λ-Na_20・XAl_2O_3 phase was formed at a high Ac/Al ratio (=3.50). Both phases changed to β, β"-alumina structure athigher temperatures (〜1200℃). The β-or β"-alumina phase with structural defects along c-axis was obtained from the γ-alumina type phase showing broad peaks. The lattice constant co of the highly defective β- or β"-alumina decreased with incieasing Na content of the precursor. On the other hand, a mixture of β- and β"-alumina phases was formed from the λ-Na_20・XAl_2O_3 phase. The volume fraction of β"-alumina in (β + β") phases was not affected by heat treatment conditions or Na content of precursors. The lattice constant c_0 of the β"-alumina in this mixture was independent of the composition of the precursor, while that of β-alumina decreased with increasing Na content.
社団法人日本セラミックス協会の論文
1991-07-01

金属アルコキシドから合成したβ、β"アルミナ前駆体の結晶化過程

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