Limits of the Thermodynamic Stability of Cobalt—Iron—Manganese Mixed Oxides at 1200°C

Authors

  • Ramesh Subramanian,

    1. Department of Materials Science and Engineering, Cornell University, Ithaca, New York 14853–1501
    Search for more papers by this author
    • *

      Member, American Ceramic society.

  • Rüdiger Dieckmann

    1. Department of Materials Science and Engineering, Cornell University, Ithaca, New York 14853–1501
    Search for more papers by this author
    • *

      Member, American Ceramic society.


  • T. O. Mason—contributing editor

  • Supported by the U.S. Department of Energy under Grant No. DE-FG0288ER45357. (This support does not constitute an endorsement by DOE of the views expressed in this article.) Supported also by the Cornell Ceramics Program. Work was performed at the Cornell Materials Science Center (supported by the National Science Foundation.)

Abstract

The thermodynamic stability of spinel and rock-salt structure phases has been investigated for the quasi-ternary mixed oxide system Co-Fe-Mn-O at 1200°C and at total pressures of the order of 1 atm (∼1.01 × 105 Pa) using thermogravimetric and electrical conductivity measurements. The results reveal the stability limits of the spinel and rock-salt structure phases with varying cationic composition and oxygen partial pressure at 1200°C. The oxygen partial pressure was varied over 12 orders of magnitude, from log10ao2= 0 to log10ao2= -12, by using CO/CO2 and N2/O2 gas mixtures and monitored by an electrochemical, stabilized zirconia-based EMF cell. The maximum cobalt mole fraction used in the investigation was about 0.33.

Ancillary