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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)

Abstract

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.

Keywords

Cation Vacancy Outer Surface Layer Outer Oxide Layer Crystalline Bulk Work Function Change 
These keywords were added by machine and not by the authors. This process is experimental and the keywords may be updated as the learning algorithm improves.

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References

  1. 1.
    B. Fisher and D.S. Tannhauser, J.Chem.Phys., 44 (1966) 1663CrossRefGoogle Scholar
  2. 2.
    R. Dieckmann, Z.Physik.Chem., Neue Folge, 10- (1977) 189Google Scholar
  3. 3.
    J. Nowotny and M. Rekas, J.Am.Ceram.Soc., sent for publicationGoogle Scholar
  4. 4.
    H.C. Chen, E. Garstein and T.O. Mason, J.Phys.Chem.Solids 43 (1982) 991CrossRefGoogle Scholar
  5. 5.
    E.M. Logothetis and J.M. Park, Solid State Comm., 43 (1982) 543CrossRefGoogle Scholar
  6. 6.
    G. Petot-Ervas, P. Ochin and T.O. Mason, “Transport in Nonstoichiometric Compounds”, V.S. Stubican and G. Simkovich, Eds., Plenum Press, London, 1985, p.61Google Scholar
  7. 7.
    A.-Z. Hed, J.Chem.Phys., 50 (1969) 2935CrossRefGoogle Scholar
  8. 8.
    G.M. Raynaud and F. Morin, J.Phys.Chem.Solids 46 (1985) 1371CrossRefGoogle Scholar
  9. 9.
    H.L. LeBrusq and J.P. Delmaire, Rev.Int.Haut.Temp.Refract., 10 (1973) 15Google Scholar
  10. 10.
    J. Nowotny, J.Chim.Phys., France, 75 (1978) 689Google Scholar
  11. 11.
    J. Nowotny, Materials Sci.Forum, 29, 99 (1988)CrossRefGoogle Scholar
  12. 12.
    J. Nowotny, Solid State Ionics, in printGoogle Scholar
  13. 13.
    J. Nowotny and M. Sloma, “Surface and Near-Surface Chemistry of Oxide Materials”, J. Nowotny and L.C Dufour, Eds., Elsevier, Amsterdam, 1988, p. 281Google Scholar
  14. 14.
    J. Nowotny, in preparation for publicationGoogle Scholar
  15. 15.
    J. Nowotny, I. Sikora and J.B. Wagner, Jr., J.Am.Ceram.Soc., 65 (1982) 192CrossRefGoogle Scholar
  16. 16.
    J. Haber, J. Nowotny, I. Sikora and J. Stoch, Appl.Surf.Sci., 17 (1984) 324Google Scholar
  17. 17.
    J. Nowotny, I. Sikora and J.B. Wagner, Jr., Mater.Sci.Monographs No 10, Elsevier, Amsterdam, 1982, p. 225Google Scholar
  18. 18.
    J. Nowotny, M. Sloma and W. Weppner, Adv.Ceram., 23 (1988)159Google Scholar
  19. 19.
    J. Nowotny and M. Sloma, J.Phys.Chem., France, C1 47 (1986) CI 807Google Scholar
  20. 20.
    E.J. Grimsey and K.A. Reynolds,J.Chem.Thermodynamics 18 (1986) 473CrossRefGoogle Scholar
  21. 21.
    J. Nowotny and M. Rekas, J.Am.Ceram.Soc., sent for publicationGoogle Scholar
  22. 22.
    A.E. Tscherkhashin, PhD thesis, Institute of Catalysis, Siberian Branch of the Sov.Acad.Sci,, Novosibirsk, 1971Google Scholar

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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