ISSN:
1600-5724
Source:
Crystallography Journals Online : IUCR Backfile Archive 1948-2001
Topics:
Chemistry and Pharmacology
,
Geosciences
,
Physics
Notes:
The potential of high-resolution electron microscopy (HREM) is demonstrated by the investigation of complex oxides with a general formula [UnMmO]- [MpO3p + l], M = (Mo, W). The HREM structure images of β-UMo2O8 agree well with the model derived from X-ray data. It is found that the γ- U3Mo20O64 sample considered earlier as a monophase appears in fact as a set of isostructural phases. The structure of these phases with MoO3 octahedral block width varying within p = 1-7 is derived from electron microscope images. Both regular and irregular substitution of cations and the formation of uranium vacancies in M-O rows are detected in γ-U3Mo20O64. Interstitial sites in the structures are detected, which can be occupied by extra U and W cations. The electron microscope images of vacancy rows give evidence for the finite length of some M-O rows. In this case oxygen dangling bonds at the ends of rows are supposed to be saturated by interstitial tungsten atoms.
Type of Medium:
Electronic Resource
URL:
http://dx.doi.org/10.1107/S0108767388004374
