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In situ high energy x-ray synchrotron diffraction study of the synthesis and stoichiometry of LaFeAsO and LaFeAsO1−xFy
Journal of Applied Physics
  • R. William McCallum, Iowa State University
  • J.-Q. Yan, Iowa State University
  • Gustav E. Rustan, Iowa State University
  • E. D. Mun, Iowa State University
  • Yogesh Singh, Iowa State University
  • S. Das, Iowa State University
  • R. Nath, Iowa State University
  • Sergey L. Bud'ko, Iowa State University
  • Kevin W. Dennis, Iowa State University
  • David C. Johnston, Iowa State University
  • Paul C. Canfield, Iowa State University
  • Matthew J. Kramer, Iowa State University
  • Andreas Kreyssig, Iowa State University
  • Thomas A. Lograsso, Iowa State University
  • Alan I. Goldman, Iowa State University
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The reaction path for the synthesis of LaFeAsO and LaFeAsO1−xFy by solid state reaction was studied by in situ high temperature x-ray diffraction technique and differential thermal analysis in the temperature interval 100 °C ⩽ T ⩽ 1150 °C. Starting with LaAs, Fe2O3, Fe, and LaF3 as precursors, the results show that the synthesis is characterized by three temperature intervals: (1) Below 500 °C the sequential reduction of Fe2O3 and Fe3O4takes place through the oxidization of LaAs. Below 400 °C, Fe2O3 is reduced to Fe3O4 by LaAs and then at 400 °C<T<500 °C Fe3O4 is further reduced to Fe. (2) In the temperature interval 500 °C<T<800 °C, multiple intermediate reactions take place resulting in the formation of FeAs and La2O3. (3) The formation of LaFeAsO based phase could be unambiguously resolved above 800 °C. For both LaFeAsO and LaFeAsO1−xFy, FeAs is a primary impurity at high temperatures that melts at ∼ 1040 °C. Possible reaction pathways and the difference between F-free and F-doped samples are discussed.


The following article appeared in Journal of Applied Physics 105 (2009): 123912, and may be found at

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American Institute of Physics
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Citation Information
R. William McCallum, J.-Q. Yan, Gustav E. Rustan, E. D. Mun, et al.. "In situ high energy x-ray synchrotron diffraction study of the synthesis and stoichiometry of LaFeAsO and LaFeAsO1−xFy" Journal of Applied Physics Vol. 105 Iss. 12 (2009) p. 123912
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