Anisotropic Oxygen Ion Diffusion in Layered PrBaCo2O5+未
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- 作者：M贸nica Burriel ; Juan Pe帽a-Mart铆nez ; Richard J. Chater ; Sarah Fearn ; Andrey V. Berenov ; Stephen J. Skinner ; John A. Kilner
- 刊名：Chemistry of Materials
- 出版年：2012
- 出版时间：February 14, 2012
- 年：2012
- 卷：24
- 期：3
- 页码：613-621
- 全文大小：621K
- 年卷期：v.24,no.3(February 14, 2012)
- ISSN：1520-5002
文摘
Oxygen diffusion and surface exchange coefficients have been measured on polycrystalline samples of the double perovskite oxide PrBaCo2O5+未 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 掳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 掳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.