Near-Surface Defect Structure of CoO in the Vicinity of the CoO/Co3O4 Phase Boundary

  • J. Nowotny
  • W. Weppner
  • M. Sloma
Part of the NATO ASI Series book series (ASIC, volume 276)


The near-surface defect structure of CoO was studied by “in situ” work function measurements in the temperature range 790 – 905°C at oxygen partial pressure near the equilibrium with Co3O4. The studies indicate that the near-surface oxide layer is enriched in cobalt interstitials which are not observed in the bulk. While CoO is oxidized and its non-stoichiometry increases, the observed phenomena in the outer surface layer may be considered within several consecutive regimes:
  1. 1

    The formation of cobalt vacancies,

  2. 2

    The formation of both cobalt vacancies and cobalt interstitials,

  3. 3

    The formation of the Co3O4 superficial layer over CoO grains,

  4. 4

    The phase transition CoO → Co3O4 in the bulk phase.


Cobalt interstitials which are formed in the outer layer of CoO at higher non-stoichiometry may be considered as precursors of the spinel phase. It has been observed that the CoO → Co3O4 phase transition within the near-surface layer takes place at \({p_{{O_2}}}\) still within the existence of the CoO phase field in the bulk. Equilibrium \({p_{{O_2}}}\)values corresponding to the bulk phase transition CoO → Co3O4 are in a good agreement with literature data.


Cation Vacancy Outer Surface Layer Outer Oxide Layer Crystalline Bulk Work Function Change 
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Copyright information

© Kluwer Academic Publishers 1989

Authors and Affiliations

  • J. Nowotny
    • 1
  • W. Weppner
    • 1
  • M. Sloma
    • 2
  1. 1.Max-Planck-Institut für FestkörperforschungStuttgart 80Germany
  2. 2.Institite of MetallurgyAcademy of Mining and MetallurgyKrakowPoland

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