Monoclinic superstructure in orthorhombic Ce10W22O81from transmission electron microscopy

Abstract

A complex rare-earth tungstate structure, present in a two-phased powder, was solved by electron diffraction, precession and high-resolution electron microscopy. The orthorhombic space groupPbnmand the atomic positions deduced from X-ray diffraction experiments were confirmed for Ce10W22O81. AC2/cmonoclinic superstructure, with cell parametersa= 7.8,b= 36.1,c= 22.2 Å and β = 100.2°, was shown and attributed to a partial oxidation of Ce3+leading to interstitial oxygen ions.