On the Interpretation of Lattice Diffusion in Magnesium Oxide
Magnesium oxide single crystals of greatly improved quality have recently become available, and techniques which permit preparation of diffusion specimens to temperatures as high as 2500°C have been developed. Data are available for cation and anion self-diffusion and tracer diffusion of 14 different impurity cations. Very different interpretations have been given these data.
Magnitudes of experimental diffusion coefficients are in fairly good agreement in the few cases in which different investigators have examined a given system. Insofar as examined, cation tracer diffusion coefficients appear to be independent of atmosphere. Recent theoretical estimates put the enthalpy for Schottky defect formation at 7 to 8 eV while the best MgO crystals of which present growth techniques are capable cannot display intrinsic behavior at any temperature below their melting point unless Hf is less than 6 eV. Interdiffusion coefficients known to be controlled by cation vacancies extrapolate smoothly to tracer values at zero concentration. It is therefore felt that there is strong evidence that the tracer-type diffusion data obtained to date represent extrinsic diffusion controlled by chemically-created vacancies, with energies of motion of the order of 2 eV. Alternative interpretations hinge on hints of structure in Arrhenius plots which may or may not be significant.
KeywordsResidual Activity Cation Vacancy Interdiffusion Coefficient Tracer Diffusion Intrinsic Diffusion
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- 1.B.J. Wuensch, Diffusion in Magnesium Oxide. Submitted to Phys. Stat. Sol.Google Scholar
- 3.I.M. Boswarva and A.D. Franklin, Theory of the Energetics of Simple Defects in Oxides, in “Mass Transport in Oxides”, (J.B. Wachtman, Jr. and A.D. Franklin, eds.) pp. 25–32, U.S. National Bureau of Standards, Special Publication 296 (1968).Google Scholar
- 5.C.R.A. Catlow, I.D. Faux and M.J. Norgett, to be published. Quoted in: A.B. Lidiard, Atomic and Ionic Transport in Ionic Crystals, in “Pure and Applied Chemistry”, Proceedings of the XXIV IUPAC Congress, Hamburg, August 1973.Google Scholar
- 6.L.W. Barr and A.B. Lidiard, Defects in Ionic Crystals, Chapter 3 in “Physical Chanaistry — an Advanced Treatise”, 10, 152–228, Academic Press, New York (1970).Google Scholar
- 7.L.W. Barr and D.K. Dawson, Correlations between Melting Temperatures and Formation and Cation Motion Energies of Schottky Defects in Ionic Crystals, Proc. British Ceramic Soc. 19, 151–160 (1971).Google Scholar
- 8.B.C. Harding, The Energy of Formation of a Schottky Defect in MgO, Phys. Lett. 40A, 227–228 (1972).Google Scholar
- 13.B.C. Harding, D.M. Price and A.J. Mortlock, Cation Self-Diffusion in Single Crystal MgO, Phil. Mag. 23, 399–408 (1971).Google Scholar
- 15.P.L. Gruzin, Dokl. Akad. Nauk. SSSR 86, 289–292 (1952).Google Scholar
- 19.L.H. Rovner, Diffusion of Oxygen in Magnesium Oxide, Ph.D. Thesis, Department of Physics, Cornell University (1966).Google Scholar
- 21.R.D. Shannon and C.T. Prewitt, Effective Ionic Radii in Oxides and Fluorides, Acta Crystallogr. B25,925–946 (1969).Google Scholar
- 32.T. Solaga, M.Sc. Thesis, Australian National University, Canberra (1972). [Quoted in reference (30)].Google Scholar
- 33.B.J. Wuensch and T. Vasilos, Diffusion in Refractory Oxides, in “Reactivity of Solids” (J.H. DeBoer et al., ed.), pp. 57–65, Elsevier Publishing Company, Amsterdam (1960).Google Scholar
- 36.B.J. Wuensch and T. Vasilos, Impurity Cation Diffusion in Magnesium Oxide, in “Mass Transport in Oxides” (J.B. Wachtman, Jr. and A.D. Franklin eds.) pp. 95–102, U.S. National Bureau of Standards, Special Publication 296 (1968).Google Scholar
- 37.H. Tagai, S. Iwai, T. Iseki and M. Saho, Diffusion of Iron, Manganese and Chromium Oxides into Single Crystal Magnesia, Radex Rundschau 1965 (4) 577–583.Google Scholar
- 47.B.J. Wuensch and T. Vasilos, Diffusion in Single-Crystal MgO Subjected to Stress, Bull. Am. Ceram. Soc. 46, 357 (1967).Google Scholar
- 48.J. Mirnkes and M. Wuttig, Diffusion of Ni2+ in MgO, J. Am. Ceram. Soc. 54, 65–66 (1971).Google Scholar
- 51.W.B. Crow, Diffusion of Cobalt, Nickel and Iron in Cobalt Oxide and Nickel Oxide, Aerospace Research Laboratories Technical Report ARL-70–0090 (June, 1970).Google Scholar