Atomic-level imaging of Mo-V-O complex oxide phase intergrowth, grain boundaries, and defects using HAADF-STEM

William D Pyrz; Douglas A Blom; Masahiro Sadakane; Katsunori Kodato; Wataru Ueda; Thomas Vogt; Douglas J Buttrey

doi:10.1073/pnas.1001239107

Atomic-level imaging of Mo-V-O complex oxide phase intergrowth, grain boundaries, and defects using HAADF-STEM

Proc Natl Acad Sci U S A. 2010 Apr 6;107(14):6152-7. doi: 10.1073/pnas.1001239107. Epub 2010 Mar 22.

Authors

William D Pyrz¹, Douglas A Blom, Masahiro Sadakane, Katsunori Kodato, Wataru Ueda, Thomas Vogt, Douglas J Buttrey

Affiliation

¹ Center for Catalytic Science and Technology, Department of Chemical Engineering, University of Delaware, Newark, DE 19716, USA.

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.