AXRD – Combination of Structural & Chemical Technique Structural (XRD) Chemical (XAS) X-rays diffract from specific planes Diffraction peak Near resonant absorption energy X-rays absorbed RESULT Diffracted peak intensity ↓ depending on elements present on diffracting planes Misra, S., Bettinger J., Anomalous X-ray Diffraction (AXRD), 5thAnnual SSRL School on Synchrotron X-ray Scattering Techniques in Materials and Environmental Sciences: Theory and Application. June 1st, 2010
f n = f 0 (Q) + f ′ (E) + i f ′ ′ (E) f 0 (Q) = normal (E independent) f ’(E) = anomalous (E dependent) f ’’(E) = absorption (E dependent) f n is the atomic scattering factor x n, y n, z n are the (fractional) positions of the n th atom Atomic scattering strength (f n ) varies near X-ray absorption edge Varying X-ray energy near absorption edge → total intensity changes f n depends on oxidation state of the element Anomalous X-ray Diffraction (AXRD) Misra, S., Bettinger J., Anomalous X-ray Diffraction (AXRD), 5thAnnual SSRL School on Synchrotron X-ray Scattering Techniques in Materials and Environmental Sciences: Theory and Application. June 1st, 2010
Inversion determines the amount of each cation found on either the tetrahedral or octahedral site, and has a big effect on the electrical properties. Mixed Spinel (0 < Normal spinel ( (Co) (Zn) (Co) B A B Inverse spinel ( (Co) (Co) (Zn) B A B Degree of Inversion Continuum
AXRD is an effective technique to characterize bulk and nanomaterials.
U.S. Department of Energy, Office of Science, through the Summer Undergraduate Laboratory Internship Program (SULI) Stanford Synchrotron Radiation Lightsource (SSRL) at SLAC National Accelerator Laboratory. My mentors Michael Toney, Sumohan Misra, and Joanna Bettinger for their guidance during the realization of my project. Stephen Rock and all the SULI staff at SLAC for give me the opportunity to work during this summer under their program.
Bettinger, J., Misra, S. Anomalous X-ray Diffraction (AXRD), California. 2010. Bettinger, J. Probing the Effects of Dopants, Defects, and Crystal Structure in Spinel Transparent Conducting Oxides for Photovoltaic Applicationsi, California. Granqvist, C. G., Transparent conductors as solar energy materials: A panoramic review, Department of Engineering Sciences, The Ångström Laboratory, Uppsala University, Uppsala, Sweeden. 2007. Introduction to X-ray Diffraction, Materials Research laboratory, University of California, Santa Barbara. 2010. Thomas, R.K., Simple Solids and their Surfaces [Online]. Available: http://rkt.chem.ox.ac.uk/tutorials/surfaces/solids.html Pecharsky, V. K., Zavalij, P.Y., Fundamentals of Powder Diffraction and Structural Characterization of Materials, Page 146-152, Springer, New York. 2005. Cullity, B.D., Stock, S.R., Elements of X-Ray Diffraction, Page 31-47, Prentice Hall, New Jersey. 2001.