Low Temperature Oxygen Transport in Nonstoichiometric CeO2
The dioxides of the f luorite structure are known to have oxygen-ion nobilities which are much greater than the cation mobilities, due to the relative ease of incorporation of oxygen vacancies [1–3]. The oxides of Ce, Pr and Tb are of special interest, since they show gross nonstoichiometric behavior ranging between the sesquioxide R2O3 (where R = Ce, Pr or Tb) and the dioxide RO2. In each of these systems the nonstoichiometric defects are believed to be oxygen vacancies. At a high enough temperature, the vacancies exist essentially at random in an otherwise perfectly ordered fluorite lattice. However, at a lower temperature (T < 500°C), a series of intermediate phases are found to occur, in which the vacancies are ordered and the symmetry of the crystal is lowered. A homologous series of the general formula Rn°2n-2 iias been proposed for these structures, mainly through studies on PrOy, where a number of such phases are observed [4–6].
KeywordsOxygen Vacancy Initial Slope Cerium Oxide Chemical Diffusion Fluorite Structure
Unable to display preview. Download preview PDF.
- 2.C. B. Alcock in “Electromotive Force Measurements in High Temperature Systems” (C.B. Alcock, ed.) p. 109, Institution of Mining and Met., London, (1968).Google Scholar
- 3.M.F. Berard, “Diffusion in Ceramic Systems: A Selected Bibliography” Ames laboratory Report #I5448 (1962).Google Scholar
- 4.J.O. Sawyer, B.G. Hyde and L. Eyring, Bull. Soc. Chim. France, 1190 (1965).Google Scholar
- 8.Y. Ban and A.S. Nowick, in “Proceedings of 5th Materials Research Symposium”, NBS special Publ. 364, p. 353 (1972).Google Scholar
- 9.J. Crank, “Mathematics of Diffusion”, p. 1ll, Oxford University Press (1967).Google Scholar
- 10.L. Eyring, in “Heterogeneous Kinetics at Elevated Temperatures” (G.R. Belton and W.L. Worrell, eds.) Plenum Press, New York, (1970).Google Scholar
- 12.B.C.H. Steele and J.M. Floyd, Proc. British Ceram. Soc., No. 19, 55 (1971).Google Scholar
- 13.B.C.H. Steele, in “Fast Ion Transport in Solids” (W. Van Gool, ed.) p. 103, North Holland, Amsterdam, (1973).Google Scholar
- 14.P. E. Childs and J. B. Wagner, Jr. in “Heterogeneous Kinetics at Elevated Temperatures” (G.R. Belton and W.L. Worrell, eds.) p. 269, Plenum Press, New York, (1970).Google Scholar
- 15.L.S. Darken, Trans. AIME, 175, 184 (1948).Google Scholar
- 16.B.C.H. Steele and C.C. Rlccardi, in “Proc. 7th Intl. Symp. on Reactivity of Solids”, Chapnan and Hall, London, (1974).Google Scholar
- 17.B.G. Hyde and L. Eyring in “Proceedings of the 4th Conference on Rare Earth Research, 1964” (L. Eyring, ed.) p. 623, Gordon and Breach, New York, (1965).Google Scholar