纳米晶(CeO_2)_(1-x)(BiO_(1.5))_x固溶体的水热合成与离子输运性质研究

Hydrothermal Synthesis and Transport Properties of Nanocrystalline (CeO 2) 1- x (BiO 1.5 ) x Solid Solution

在２４０℃水热体系中首次合成出系列纳米晶固溶体（ＣｅＯ２）１－ｘ（ＢｉＯ１．５）ｘ（ｘ＝０．０～０．５０）．产物采用Ｘ射线衍射，扫描电子显微镜和Ｘ射线光电子能谱仪进行表征．Ｂｉ２Ｏ３在ＣｅＯ２中的固溶限约为５０％．所有固溶体结晶属立方萤石结构，粒度范围为１０～１８ｎｍ．当Ｂｉ２Ｏ３掺杂量小于固溶限时，于８００℃烧结不会导致结构转变．而对于（ＣｅＯ２）０．５（ＢｉＯ１．５）０．５，于８００℃在空气中烧结将导致固溶限降低．Ｂｉ２Ｏ３含量低于固溶限时，固溶体只具有体电导，而（ＣｅＯ２）０．６（ＢｉＯ１．５）０．４的总电导可分为体电导和晶界电导．体电导为氧离子。

By means of XRD and XPS measurements, the structural characteristics and valence states of a series of nanocrystalline solid solutions(CeO 2) 1- x (BiO 1.5 ) x ( x =0 0￣0 50) synthesized under mild hydrothermal conditions at 240 ℃ were investigated. The solution limit of Bi 2O 3 in ceria is as high as ca . 50 %. XRD data showed that all solid solutions crystallized in single phase cubic fluorite type structure. This result is different from the solid state reaction routes. The average grain size of all solid solutions was within a narrower range of 10￣18 nm. XPS data gave evidence of the presence of Bi(Ⅲ) and Ce(Ⅳ) in all doped ceria. When the content of dopant Bi 2O 3 in ceria was lower than the limit, air firing of the as made doped ceria up to 800 ℃ did not lead to any structural transformation. For the solid solution of (CeO 2) 0.5 (BiO 1.5 ) 0.5 , sintering it in air at 800 ℃ would cause the limit exceeded as well as segregation of an unknown phase. The ionic conduction measured by impedance spectroscopy showed that the solid solutions with bismuth content lower than the limit exhibited only the bulk conduction. The bulk conduction of solution(CeO 2) 0.6 (BiO 1.5 ) 0.4 was due to oxide ions and the grain boundary to silver from the electrode.