SmAlO
3 was synthesized by the TW method. As the starting solution, each aqueous solution of Al(NO
3)
39H
2O and Sm(NO
3)
36H
2O was dissolved in proper amount of distilled water. Various quantities of Si(OC
2H
5)
4)(TEOS) and a small amount of 2M-HCl as catalysis were mixed into the starting solution. In a sample obtained by heating the gel with TEOS of 0.90×10
-2 mol for 30 min, pure SmAlO
3 in a single phase was not obtained at the temperature of 1100°C, because the obtained sample had each small amount of SmO and β-Cristobalite liberated from SmSiO
3. It was thought that SmAlO
3 was formed as a degradation product of Sm
4Al
2O
9, simultaneously as a product of the reaction of γ-Al
2O
3 and Sm
2O
3 in the progress of its decomposition when the decomposition of SmSiO
3 proceeded in preference to the degradation of Sm
4Al
2O
9. From comparison of their X-ray diffraction patterns for samples with two kinds of TEOS content consisting of 1.35×10
-2 mol and 0.90×10
-2 mol, it was thought that α-Al
2O
3 was transformed into γ-Al
2O
3.
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