IMI Interdisciplinary Mathematics InstituteCollege of Arts and Sciences

Imaging in Electron Microscopy II

Thomas Vogt
University of South Carolina

Scanning Transmission Electron Microscopy Investigations of Complex Oxides Used as Oxidation Catalysts

  • Feb. 21, 2010
  • 9:30 a.m.
  • Sumwalt 102

High-Angle-Annular-Dark-Field/Scanning Transmission Electron Microscopy (HAADF/ STEM) is a technique uniquely suited for detailed studies of the structure and composition of complex oxides. The HAADF detector collects electrons which have interacted closely with the nucleus of the atoms in the specimen and therefore resembles the better known Z2 (Z is atomic number) Rutherford scattering. Molybdenum-based suboxides have been a subject of extensive research for several decades. One class consists of bronzes based on pentagonal {Mo6O21} building units; these include Mo5O14 and Mo17O47. In the last 20 years, new materials doped with a variety of substitution elements, but built upon the same structural building units, have attracted significant interest for catalytic applications. These applications include the selective oxidation of light paraffins and olefins, as well as the partial oxidation of methanol. Depending on the species substituted and the combination of phases present, catalytic performance seems to vary significantly. We present HAADF-STEM investigations of various complex oxide phases and show that we can for example distinguish metal-containing sites within these structurally and compositionally complex-oxides through the analysis of contrast.

*Collaboration with Douglas Blom (University of South Carolina), Bill Pyrz and Douglas Buttrey (University of Delaware)

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