EXAFS analyses of CaTiO3 doped with Ce, Nd and U

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 (Ca1-xCex)TiO3 (x = 0.10, 0.20), (Ca1-xNdx)TiO3 (x = 0.05, 0.10, 0.15, 0.20) and (Ca1-xUx)(Ti1-2xAl2x)O-3 (x = 0, 0.05). With increasing neodymium content in (Ca1-xNdx)TiO3 the first nearest titanium-oxygen distances decreased. On the other hand, with increasing cerium content in (Ca1-xCex)TiO3, the first nearest titanium-oxygen distances increased. The first nearest titanium-oxygen distance in (Ca1-xUx)(Ti1-2xAl2x)O-3 was larger than that in undoped CaTiO3. 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 CaTiO3 is larger than those of Nd-doped and undoped CaTiO3. The experimental results on the leaching rates of doped and undoped CaTiO3 were consistent with this estimation. The structural change of (Ca0.80Ce0.20)TiO3 after a leaching test in HCl at 363 K for 140 days was also measured by X-ray diffraction and XANES analysis. (C) 1998 Elsevier Science B.V. All rights reserved.