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.  diffraction patterns showed a pair of diffuse spots in the  direction at both sides of the 1/21/21/2 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 (110) plane is described by compositional waves of Y3+/Nb5+ and O2-/vacancy and displacive waves of Y3+ + Nb5+ and O2- along the  direction. The composition at cation sites is expressed by a sinusoidal wave with occupation changes between Y and 0.58Y + 0.42Nb. The occupation 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.
ASJC Scopus subject areas
- Biochemistry, Genetics and Molecular Biology(all)