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18O and 2H diffusion has been investigated at a temperature of 300 °C in the double perovskite material PrBaCo2O5+δ (PBCO) in flowing air containing 200 mbar of 2H216O. Secondary ion mass spectrometry (SIMS) depth profiling of exchanged ceramics has shown PBCO still retains significant oxygen diffusivity (~1.3 × 10−11 cm2s−1) at this temperature and that the presence of water (2H216O), gives rise to an enhancement of the surface exchange rate over that in pure oxygen by a factor of ~3. The 2H distribution, as inferred from the 2H216O− SIMS signal, shows an apparent depth profile which could be interpreted as 2H diffusion. However, examination of the 3-D distribution of the signal shows it to be nonhomogeneous and probably related to the presence of hydrated layers in the interior walls of pores and is not due to proton diffusion. This suggests that PBCO acts mainly as an oxygen ion mixed conductor when used in PCFC devices, although the presence of a small amount of protonic conductivity cannot be discounted in these materials. [ABSTRACT FROM AUTHOR]

Abstract: Oxygen tracer diffusion coefficient (D ⁎) and surface exchange coefficient (k ⁎) have been measured for (La0.75Sr0.25)0.95Cr0.5Mn0.5O3−δ using isotopic exchange and depth profiling by secondary ion mass spectrometry technique as a function of temperature (700–1000 °C) in dry oxygen and in a water vapour-forming gas mixture. The typical values of D ⁎ under oxidising and reducing conditions at ∼1000 °C are 4×10−10 cm2 s−1 and 3×10−8 cm2 s−1 respectively, whereas the values of k ⁎ under oxidising and reducing conditions at ∼1000 °C are 5×10−8 cm s−1 and 4×10−8 cm s−1 respectively. The apparent activation energies for D ⁎ in oxidising and reducing conditions are 0.8 eV and 1.9 eV respectively. [Copyright &y& Elsevier]

Abstract: The oxygen tracer diffusion coefficient (D⁎) has been measured for 9 mol% scandia 2 mol% yttria co-doped zirconia solid solution, (Y2O3)2(Sc2O3)9(ZrO2)89, using isotopic exchange and line scanning by Secondary Ion Mass Spectrometry, as a function of temperature. The values of the tracer diffusion coefficient are in the range of 10−8–10−7 cm2 s−1 and the Arrhenius activation energy was calculated to be 0.9 eV; both valid in the temperature range of 600–900 °C. Electrical conductivity measurements were carried out using 2-probe and 4-probe AC impedance spectroscopy, and a 4-point DC method at various temperatures. There is a good agreement between the measured tracer diffusion coefficients (D⁎, Ea=0.9 eV) and the diffusion coefficients calculated from the DC total conductivity data (D σ , Ea=1.0 eV), the latter calculated using the Nernst–Einstein relationship. [Copyright &y& Elsevier]