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Issue 19, 2015
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Oxygen diffusion in single crystal barium titanate

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Abstract

Oxygen diffusion in cubic, nominally undoped, (100) oriented BaTiO3 single crystals has been studied by means of 18O2/16O2 isotope exchange annealing and subsequent determination of the isotope profiles in the solid by time-of-flight secondary ion mass spectrometry (ToF-SIMS). Experiments were carried out as a function of temperature 973 < T/K < 1173, at an oxygen activity of aO2 = 0.200, and as a function of oxygen activity 0.009 < aO2 < 0.900 at T = 1073 K. The oxygen isotope profiles comprise two parts: slow diffusion through a space-charge zone at the surface depleted of oxygen vacancies followed by faster diffusion in a homogeneous bulk phase. The entire isotope profile can be described by a single solution to the diffusion equation involving only three fitting parameters: the surface exchange coefficient ks*, the space-charge potential Φ0 and the bulk diffusion coefficient D*(∞). Analysis of the temperature and oxygen activity dependencies of D*(∞) and Φ0 yields a consistent picture of both the bulk and the interfacial defect chemistry of BaTiO3. Values of the oxygen vacancy diffusion coefficient DV extracted from measured D*(∞) data are compared with literature data; consequently a global expression for the vacancy diffusivity in BaTiO3 for the temperature range 466 < T/K < 1273 is obtained, with an activation enthalpy of vacancy migration, ΔHmig,V = (0.70 ± 0.04) eV.

Graphical abstract: Oxygen diffusion in single crystal barium titanate

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Publication details

The article was received on 27 Feb 2015, accepted on 07 Apr 2015 and first published on 14 Apr 2015


Article type: Paper
DOI: 10.1039/C5CP01187F
Phys. Chem. Chem. Phys., 2015,17, 12587-12597

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    Oxygen diffusion in single crystal barium titanate

    M. Kessel, R. A. De Souza and M. Martin, Phys. Chem. Chem. Phys., 2015, 17, 12587
    DOI: 10.1039/C5CP01187F

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