CexZr1-xO2(1>x>0，簡稱CZ)的固溶體是汽車觸媒轉換器中常見的助(促)催化添加劑(promoter)材料，是為改良氧化鈰(ceria，CeO2)之耐熱性及釋氧能力而添加Zr離子於CeO2結構中之儲氧性材料(oxygen storage capacity, OSC)。而因Ce、Zr離子兩者的半徑差異，以及常溫常壓下氧化物的結構差異，使CZ固溶相系統呈現熱力學介穩態，受熱及能量即可能造成相分離及影響儲氧性。
以γ-Al2O3為載體夾帶CZ微粒之複合粉末材料（簡稱A/CZ），可進一步改善CZ儲/釋氧功能及熱穩定性，並可兼具高比表面積特性。製作此一粉末，目前研究以濕化學法為主流，因其可製得高均勻度且粒徑小、分布窄之成品。
本研究使用初濕含浸法(incipient-wetness impregnation) 合成CexZr1-xO2 (x=0.6)固溶體。採用不同Al2O3 (單水鋁石)：CexZr1-xO2配比之漿料，觀察熱處理後A/CZ複合材料之CZ以及Al2O3互相作用之結果。研究結果顯示A與CZ混合比例會影響生成之CZ固溶比(Ce:Zr)，Al2O3比例越高則CZ固溶之比例(Ce:Zr)越趨近6:4。而對於熱穩定性的影響則是，當Al2O3(A)：CexZr1-xO2(CZ)配比中之Al2O3比例高於或低於60%都會發生相分離。若以球形混合配位數模型，來探討A:CZ混合比例對CZ晶徑變化及熱穩定性之影響，可發現Al2O3比例低於70%時，CZ粒子有較大機率互相接觸，導致CZ晶粒較高機會粗化，因此也較易產生相分離。Al2O3比例高於70%時，則會因為Al2O3比例較高導致CZ被Al2O3阻擋而不易擴散成長，因此CZ晶粒不易粗化，而Zr離子因半徑小較不受Al2O3限制，因此在低溫即有Zr-rich相產生。
釋氧能力則與CZ中之Ce-rich晶粒之相對生成量，及其晶徑大小有關，從結果顯示當Ce-rich固溶體(CexZr1-xO2，0.75≧x≧0.6)之相對生成量越多，則釋氧能力較高，不過隨晶粒成長越大則釋氧能力會隨之下降。

SUMMARY

CexZr1-xO2 (1>x>0, CZ) solid solution is an oxygen storage capacity (OSC) material which can be applied in three-way catalysts to promote emission conversion efficiency in gasoline-fuelled automobiles and motorcycles. But, CZ appeared OSC deteriorated after high temperature treatments, it often refers to the phase separation and sizes growth of CZ.

In this research, we observe the CZ particles growth in boehmite slurry by using the incipi-ent-wetness impregnation in various Al2O3 : CZ proportions. We found that the Al2O3 propor-tions could affect Zr concentration in CZ and the sizes growth of CZ, that at A0.7/(CZ)0.3 can approach the target concentration. Furthermore, we investigated that the oxygen storage ca-pacity that affected by CZ sizes and Ce-rich relative capacity, and the thermal stability of CZ after durability tests.

Key words: CexZr1-xO2, ACZ, impregnation, boehmite

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