EXAFS analyses of CaTiO 3 doped with Ce, Nd and U

Abstract

The EXAFS (extended X-ray absorption fine structure) analyses were carried out for Ti–K, Ce–L3, Nd–L3 and U–L3 edges to make clear the local structures in (Ca 1− x Ce x )TiO 3 ( x=0.10, 0.20), (Ca 1− x Nd x )TiO 3 ( x=0.05, 0.10, 0.15, 0.20) and (Ca 1− x U x )(Ti 1−2 x Al 2 x )O 3 ( x=0, 0.05). With increasing neodymium content in (Ca 1− x Nd x )TiO 3 the first nearest titanium–oxygen distances decreased. On the other hand, with increasing cerium content in (Ca 1− x Ce x )TiO 3, the first nearest titanium–oxygen distances increased. The first nearest titanium–oxygen distance in (Ca 1− x U x )(Ti 1−2 x Al 2 x )O 3 was larger than that in undoped CaTiO 3. With increasing dopant content, the first nearest dopant (cerium or neodymium)–oxygen distances increased. From the result of the compositional dependencies of bonding length (cation–oxygen distance), which is inversely proportional to the bonding energy, it is estimated that magnitude of the leaching rate of Ce-doped CaTiO 3 is larger than those of Nd-doped and undoped CaTiO 3. The experimental results on the leaching rates of doped and undoped CaTiO 3 were consistent with this estimation. The structural change of (Ca 0.80Ce 0.20)TiO 3 after a leaching test in HCl at 363 K for 140 days was also measured by X-ray diffraction and XANES analysis.