Atomic-level imaging of Mo-V-O complex oxide phase intergrowth, grain boundaries, and defects using HAADF-STEM.
basic_science · Level V
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- Record sourced from PubMed, PMID 20308579.
- Also identified by DOI 10.1073/pnas.1001239107 and PMC identifier 2851970.
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Abstract
In this work, we structurally characterize defects, grain boundaries, and intergrowth phases observed in various Mo-V-O materials using aberration-corrected high-angle annular dark-field (HAADF) imaging within a scanning transmission electron microscope (STEM). Atomic-level imaging of these preparations clearly shows domains of the orthorhombic M1-type phase intergrown with the trigonal phase. Idealized models based on HAADF imaging indicate that atomic-scale registry at the domain boundaries can be seamless with several possible trigonal and M1-type unit cell orientation relationships. The alignment of two trigonal domains separated by an M1-type domain or vice versa can be predicted by identifying the number of rows/columns of parallel symmetry operators. Intergrowths of the M1 catalyst with the M2 phase or with the Mo(5)O(14)-type phase have not been observed. The resolution enhancements provided by aberration-correction have provided new insights to the understanding of phase equilibria of complex Mo-V-O materials. This study exemplifies the utility of STEM for the characterization of local structure at crystalline phase boundaries.