酸化アルミニウムマンガン中のMn^<3+>生成に及ぼす焼成雰囲気の影響(<小特集>セラミック材料小特集)

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The lattice constants and the molar fractions of Mn^<3+> ions in manganese aluminum oxides heat-treated under various oxygen partial pressures (Po_2) were measured and the effects of the atmosphere of heat-treatment on the valence and the coordination state of manganese ions were investigated. Manganese carbonate and α-alumina were mixed in an equivalent ratio, and the mixture was heat-treated at 1400℃, 1300℃, or 1200℃ under various Po_2 from 2.1×10^<-1>atm to 2.7×10^<-14>atm. The lattice constants of the manganese aluminum oxides obtained were determined precisely. For two kinds of samples, the change of weight was measured at 1400℃, 1300℃, or 1200℃ under various Po_2, and then the molar fractions of Mn^<3+> ions in these samples were obtained as a function of Po_2. The lattice constants and the molar fraction of Mn^<3+> ions changed similarly with Po_2, i.e. they were almost constant at low Po_2, increased abruptly at a certain Po_2, and then increased gradually with increasing Po_2. It is supposed that the substitution of Al^<3+> ions by Mn^<3+> ions taking place at high Po_2 caused the increase of lattice constants. The abrupt increase in molar fraction of Mn^<3+> ions and the lattice constants is interpreted as follows: At low Po_2 the distribution of cations in the spinel structure is normal as Mn^<3+> ions have the tetrahedral site preference. The increase of Po_2 favors the formation of Mn^<3+> ions, which prefer the octahedral sites. Therefore, the structure becomes intermediate between the normal and the inverse, and the molar fraction of Mn^<3+> ions and the lattice constants increased abruptly.
社団法人日本材料学会の論文
1983-11-15

酸化アルミニウムマンガン中のMn^<3+>生成に及ぼす焼成雰囲気の影響(<小特集>セラミック材料小特集)

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