ISSN:
1600-5724
Source:
Crystallography Journals Online : IUCR Backfile Archive 1948-2001
Topics:
Chemistry and Pharmacology
,
Geosciences
,
Physics
Notes:
The rare-earth metal oxides are known to exhibit several phases which can be either stoichiometric or nonstoichiometric. One such phase which has been recently found to exist in thin-film form corresponds to the monoxide phase RO. The oxygen content in this phase, however, has been found to vary such that the phase actually has the stoichiometry ROx with 1 〈 x 〈 2. The present paper deals with electron diffraction studies of the SRO → LRO transition in the nonstoichiometric ROx phase. This transition commences as a result of the creation of oxygen vacancies in the as-grown thin-film phase, when this phase is pulse annealed with an electron beam in the electron microscope, the annealing temperature being about 500°C. The short-range ordered version is manifested by the appearance of curious diffuse streaks on the diffraction patterns. The diffuse intensity distribution has been found to be situated on a complicated surface (rhombic dodecahedron) in the reciprocal space of the initial f.c.c. phase with a = 5.09 ± 0.05 Å and 5.37 ± 0.05 Å for erbium and dysprosium oxides respectively. On further pulse annealing at a higher temperature ( ̃900°C), the short-range ordered version yields to give rise to a long-range ordered superlattice phase which corresponds to the bulk-like b.c.c. phase with a = 10.41 ± 0.05 Å and 10.18 ± 0.05 Å for erbium and dysprosium oxides respectively. The SRO → LRO transition has also been analysed in terms of the stoichiometric variations resulting from the pulse annealing.
Type of Medium:
Electronic Resource
URL:
http://dx.doi.org/10.1107/S0567739477002368
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