Ce K-edge EXAFS study of nanocrystalline CeO_2

摘要

Nanocrystalline CeO_2 samples were prepared via precipitation from aqueous cerium(IV) sulfate solution under a controlled pH. After being subjected to calcination at various temperatures to yield different particle sizes, the local structure around Ce atom was investigated by using EXAFS spectroscopy at Ce K-edge. The first shell Ce-O distance was found to be slightly shorter with small CeO_2 particles, indicating a contraction of the lattice. There exists a significant growth in coordination number of the second cell Ce-Ce when the particle size became larger. In terms of Debye-Waller factor (σ~2), the first three coordination shells showed a consistent trend, i.e. the degree of disorder increases with reduced particle size. Moreover, σ~2 of the second shell was found to be smaller than that of the first shell for all samples.