Get access

Scaling of extended defects in nano-sized Brownmillerite CaFeO2.5

Authors

  • Kapil Gupta,

    1. Department of Physics, Nano Functional Materials Technology Centre and Materials Science Research Centre, Indian Institute of Technology, Chennai, India
    Search for more papers by this author
    • These authors contributed equally to this work.
  • Shubra Singh,

    1. University of Montpellier 2, Institut Charles Gerhardt, UMR 5253, C2M, Montpellier, France
    2. Crystal Growth Centre, Anna University, Chennai, India
    3. Sciences Chimiques de Rennes, UMR 6226, Inorganic Materials: Soft Chemistry and Reactivity of Solids, University of Rennes 1, Rennes, France
    Search for more papers by this author
    • These authors contributed equally to this work.
  • Monica Ceretti,

    1. University of Montpellier 2, Institut Charles Gerhardt, UMR 5253, C2M, Montpellier, France
    Search for more papers by this author
  • M.S. Ramachandra Rao,

    Corresponding author
    • Department of Physics, Nano Functional Materials Technology Centre and Materials Science Research Centre, Indian Institute of Technology, Chennai, India
    Search for more papers by this author
  • Werner Paulus

    Corresponding author
    • University of Montpellier 2, Institut Charles Gerhardt, UMR 5253, C2M, Montpellier, France
    Search for more papers by this author

Corresponding author: e-mail msrrao@iitm.ac.in, Phone: +91 44 22574872, Fax: +91 44 22574852

e-mail werner.paulus@univ-montp2.fr, Phone: +33 4 67 14 45 59, Fax: +33 4 67 14 40 92

Abstract

We investigated the formation of extended defects in CaFeO2.5, predominantly appearing as antiphase boundaries (APBs), as a function of the synthesis method and temperature. While CaFeO2.5 is known to adopt an ordered oxygen defect structure showing long range order of the (FeO4) chains in its bulk form, interestingly, we demonstrated that the length of these (FeO4) chains can be considerably scaled down to few nanometers by adopting a modified sol–gel method (low temperature synthesis) while the grain size of the resulting nano-phase CaFeO2.5 is around 50 nm. We discuss the synthesis dependent modulation of the length of APBs, characterized by X-ray diffraction and high resolution TEM, to be at the origin of an amplified switching dynamics of the (FeO4) chains. This can accordingly explain the reduction of the onset temperature for oxygen diffusion to set in from 450 °C for bulk-CaFeO2.5 to 320 °C for nano-CaFeO2.5, as determined by 18O/16O oxygen isotope exchange reactions.

Get access to the full text of this article

Ancillary