Origin of the superstructure elucidated by atomic resolution HAADF-STEM and HREM in the Ce_(10)W_(22)O_(81) lanthanide tungstate phase

摘要

The present paper provides new information on the attribution of the cationic sites of the orthorhombic Ce_(10)W_(22)O_(81) crystal phase prepared in the CeO_2-Ce_2O_3-WO_3 ternary system. Atomic resolution HAADF-STEM (high-angle annular dark-field scanning transmission electron microscopy) and HREM (high-resolution electron microscopy) investigations have highlighted the presence of two mixed columns of Ce and W cations along the a axis that were previously assigned to pure W cations in the asymmetric unit. This discovery explains the presence of a commensurate superstructure doubling the orthorhombic unit-cell length a_o.