Electronic Resource
Copenhagen
:
International Union of Crystallography (IUCr)
Applied crystallography online
30 (1997), S. 272-279
ISSN:
1600-5767
Source:
Crystallography Journals Online : IUCR Backfile Archive 1948-2001
Topics:
Geosciences
,
Physics
Notes:
Modulated structures formed in defect fluorite-type (Y2O3)1 − x(Nb2O5)x (0.21 ≤ x ≤ 0.27) solid solutions have been investigated by electron diffraction. [1{\bar 1}0] diffraction patterns showed a pair of diffuse spots in the [11{\bar 2}] direction at both sides of the ½½½ reciprocal-lattice point. The distance between the diffuse spots decreased from 0.064 to 0.045 Å−1 with increasing x from 0.21 to 0.27. High-resolution electron microscopy images revealed the existence of small domains with an antiphase structure. The two-dimensional antiphase structure projected on the (1{\bar 1}0) plane is described by compositional waves of Y3+/Nb5+ and O2−/vacancy and displacive waves of Y3+ + Nb5+ and O2− along the [11{\bar 2}] direction. The composition at cation sites is expressed by a sinusoidal wave with occupation changes between Y and 0.58Y + 0.42Nb. The occupational probability of O at anion sites is also expressed by a sinusoidal wave with occupation changes between 0.806 and 0.904. Amplitudes of the displacive waves for anions and cations were determined to be about 0.3 and 0.02 Å, respectively.
Type of Medium:
Electronic Resource
URL:
http://dx.doi.org/10.1107/S0021889896013283
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