Anisotropic Oxygen Ion Diffusion in Layered PrBaCo2O5+delta

作者：Burriel Monica^*; Pena Martinez Juan; Chater Richard J; Fearn Sarah; Berenov Andrey V; Skinner Stephen J; Kilner John A

来源：Chemistry of Materials, 2012, 24(3): 613-621.

DOI：10.1021/cm203502s

• anisotropy
• oxygen diffusion
• layered cobaltites
• double perovskites
• mixed conductors (MIEC)
• cathodes
• solid oxide fuel cells (SOFC)

Oxygen diffusion and surface exchange coefficients have been measured on polycrystalline samples of the double perovskite oxide PrBaCo2O5+delta by the isotope exchange depth profile method, using a time-of-flight SIMS instrument. The measured diffusion coefficients show an activation energy of 1.02 eV, as compared to 0.89 eV for the surface exchange coefficients in the temperature range from 300 to 670 degrees C. Inhomogeneity was observed in the distribution of the oxygen-18 isotopic fraction from grain to grain in the ceramic samples, which was attributed to anisotropy in the diffusion and exchange of oxygen. By the use of a novel combination of electron back scattered diffraction measurements, time-of-flight, and focused ion beam SIMS, this anisotropy was confirmed by in-depth analysis of single grains of known orientation in a ceramic sample exchanged at 300 degrees C. Diffusion was shown to be faster in a grain oriented with the surface normal close to 100 and 010 (ab-plane oriented) than a grain with a surface normal close to 001 (c-axis oriented). The magnitude of this anisotropy is estimated to be close to a factor of 4, but this is only a lower bound due to experimental limitations. These findings are consistent with recent molecular dynamic simulations of this material where anisotropy in the oxygen transport was predicted.

• 出版日期2012-2-14