Layered Atomic Arrangements in Complex Oxides: Physical Property Implications

Friday, December 4, 2009 - 11:00 p.m. to Saturday, December 5, 2009 - 12:00 a.m.
CHEMS SEMINAR

Featuring Kurt Sickafus, Ph.D.
Materials Science and Technology Division
Los Alamos National Laboratory

Location:  DBH 1500
Free and open to the public

Abstract:
In this presentation, I will introduce a novel atomic layer stacking model to describe systematically the crystal structures of numerous complex materials (1).  I will illustrate the efficacy of this model by considering the property of radiation damage resistance in a few selected oxides.  These concepts have implications for the development of future nuclear fuel and waste forms, but also may be applied to the development of advanced fuel cells and to materials with high-temperature creep resistance.

To illustrate the layer stacking concept, I will consider a sequence of MxOy oxide compounds in which the metal cations progress in oxidation state from monovalent (M1+) to octavalent (M8+).  I will use concepts relating to geometric subdivisions of a triangular atom net to describe the layered atom patterns in these compounds (concepts originally proposed by Shuichi Iida(2)).  I will demonstrate that as a function of increasing oxidation state (from M1+ to M4+), the layer stacking motifs used to generate each successive structure (specifically, motifs along a  symmetry axis, such as the kagome, woven basket pattern shown right), progress through the following sequence: MOM, MO, ,oMo, OMO (where M and O represent fully-dense triangular atom nets, while m and o represent partially-filled triangular atom nets).  Much of the “action” associated with diffusion and radiation damage behavior in these oxides (and other thermophysical properties as well) is centered in the partially-filled, m and o, layers.

1 K.E. Sickafus et al. “Layered Atom Arrangements in Complex Materials,” Los Alamos Series Report # LA-14205, 2006.
2 S. Iida, "Layer Structures of Magnetic Oxides," J. Phys. Soc. Japan 12 (3) (1957) 222-233.


About the Speaker:
Kurt Sickafus is a technical staff member at Los Alamos National Laboratory, in the Materials Science and Technology Division. He is also an Adjunct Professor at the New Mexico Institute of Mining & Technology in the Department of Materials Engineering, and a part-time instructor at the University of New Mexico – Los Alamos Campus.

Sickafus is a Fellow of Los Alamos National Laboratory and a Fellow of the American Ceramic Society. He is a member of the Editorial Board of the Journal of Nuclear Materials and a member of 10 technical societies: The Böhmische Physical Society, The Materials Research Society, The American Nuclear Society, The American Chemical Society, The American Physical Society, The Mineralogical Society of America, The Microscopy Society of America, The Minerals, Metals, and Materials Society, The Institute of Physics (Great Britain), and The Royal Microscopical Society (Great Britain).

Sickafus has been an experimental researcher in the field of materials science for about 25 years, investigating structure and properties in metals, polymers, and ceramics, in bulk, thin-film, and composite forms. Sickafus graduated from Ohio Wesleyan University in 1978 (B.A. degree in physics and mathematics). He received his Ph.D. degree from Cornell University in 1985 (materials science and engineering). Sickafus also worked as a postdoctoral research assistant in the Cavendish Laboratory, University of Cambridge (1985-1987) and as a staff member at I.B.M. (1987-88) before joining Los Alamos National Laboratory in 1989. Sickafus’s primary experimental expertise is in electron microscopy, with an emphasis on transmission electron microscopy (TEM), scanning transmission electron microscopy (STEM), and analytical electron microscopy (AEM) techniques. Sickafus’s research interests are primarily in the areas of crystallography, radiation damage effects, and microstructure of materials. Currently, his research is concentrated on the radiation damage behavior of oxides with structures ranging from spinel to ilmenite to pyrochlore to fluorite to perovskite.

Relevant publications:
1.  K. E. Sickafus et al., "Radiation tolerance of complex oxides," Science 289 (2000) 748.
2.  K. E. Sickafus et al., "Radiation-induced amorphization resistance and radiation tolerance in structurally-related oxides," Nature Mater. 6 (2007) 217.