還元処理によるセリアージルコニア固溶体の酸素貯蔵能の向上

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The function of oxygen storage capacity (OSC) is very important to improve a performance for an automobile exhaust catalyst. CeO_2-ZrO_2 solid solution has an excellent OSC, and is available for a catalytic promoter. In this paper, OSC of the CO reduced CeO_2-ZrO_2 solid solution having various composition loaded with Pt was estimated by thermo gravimeter, and the phases and the crystalline structure of the reduced CeO_2-ZrO_2 solid solution were studied by X-ray diffraction method. The maximum total OSC-value of the reduced material occurs at the composition of 50 mol% CeO_2-50 mol% ZrO_2. The maximun value is about 753 μmol O_2/g-solid solution, which is about twice the value (416 μmol O_2/g-solid solution) of the attrition-milled CeO_2-ZrO_2 solid solution, and 5 times higher than that (150 μmol O_2/g-solid solution) of the material synthesized by conventional impregnation. The reduced material consists of Ce_2Zr_2O_8 and CeO_2 solid solution in the composition range from 30 to 50 mol% ZrO_2. The reduced material consists of the mixture, Ce_2Zr_2O_8 and ZrO_2 in the composition range from 50 mol% ZrO_2 to 100 mol% ZrO_2. The presence of Zr^<4+> near Ce^<4+> makes the expansion easier enhancing further valence change, because Zr^<4+> is very small in volume. Regular distribution of Ce and Zr ions would make it possible to place Zr^<4+> in the nearest position to Ce ion. This would be the reason why the partial OSC of Ce_2Zr_2O_8 is much higher than the complete solid solution.
社団法人日本セラミックス協会の論文
2002-02-01

還元処理によるセリアージルコニア固溶体の酸素貯蔵能の向上

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