Hydrothermal synthesis and transport properties of nanocrystalline (CeO2)(1-x)(BiO1.5)(x) solid solution

By means of XRD and XPS measurements, the structural characteristics and va lence states of a series of nanocrystalline solid solutions(CeO2)(1-x)(BiO1 .5)(x)(x = 0.0 similar to 0.50) Synthesized under mild hydrothermal conditi ons at 240 degrees C were investigated. The solution limit of Bi2O3 in ceri a is as high as ca, 50 %, XRD data showed that all solid solutions crystall ized in single phase cubic fluorite-type structure. This result is differen t from the solid state reaction routes. The average grain size of all solid solutions was within a narrower range of 10 similar to 18 nm. XPS data gav e evidence of the presence of Bi(II) and Ce(IV) in all doped ceria, When th e content of dopant Bi2O3 in ceria was lower than the limit, air firing of the as-made doped ceria up to 800 degrees C did not lead to any structural transformation. For the solid solution of (CeO2)(0.5)(BiO1.5)0.5, sintering it in air at 800 degrees C would cause the limit exceeded as well as segre gation of an unknown phase, The ionic conduction measured by impedance spec troscopy showed that the solid solutions with bismuth content lower than th e limit exhibited only the bulk conduction. The bulk conduction of solution (CeO2)(0.6)(BiO1.5)(0.4) was due to oxide ions and the grain boundary to si lver from the electrode.