Long- and short-range order in stuffed titanate pyrochlores
Journal Article
·
· Journal of Solid State Chemistry
- Department of Chemistry, Princeton University, Princeton, NJ 08544 (United States)
- NIST Center for Neutron Research, NIST, Gaithersburg, MD 20899 (United States)
- Department of Materials Science, Delft University of Technology, Rotterdamseweg 137, 2682 AL Delft (Netherlands)
We report a structural study of the stuffed pyrochlore series Ln{sub 2}(Ti{sub 2-x}Ln{sub x})O{sub 7-x/2} (Ln=Ho, Yb; 0{<=}x{<=}0.67). Electron microscopy and Rietveld refinements of neutron powder diffraction data for the x=0.67 end members, Ho{sub 2}TiO{sub 5} and Yb{sub 2}TiO{sub 5}, reveal that small domains ({approx}50 A or less) exist where the Ln and Ti/Ln sublattices are pyrochlore like, while the average structure is fluorite like. Both the Ho and Yb stuffed pyrochlore series for 0.1{<=}x{<=}0.5 are shown to be a composite of long- and short-range-ordered pyrochlore phases. The relative fraction of long-range vs. short-range pyrochlore order decreases with increasing Ln doping. An additional complex structural modulation of the pyrochlore structure is observed in electron diffraction and high-resolution electron microscopy images. - Graphical abstract: The <110> zone axis electron diffraction pattern for Ho{sub 2}TiO{sub 5} reveals the coexistence of long- and short-range pyrochlore ordering. An additional complex modulation of the pyrochlore structure consisting of a seven-fold enlargement of the unit cell in the (662) direction is also observed.
- OSTI ID:
- 21043858
- Journal Information:
- Journal of Solid State Chemistry, Journal Name: Journal of Solid State Chemistry Journal Issue: 1 Vol. 181; ISSN 0022-4596; ISSN JSSCBI
- Country of Publication:
- United States
- Language:
- English
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