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arXiv 1704.02243cond-mat.mtrl-scicond-mat.other
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声子对BaZrO3中O空位自由迁移能的贡献

Importance of phonon contribution to the free migration energy of the O vacancy in BaZrO3

N. Raja, D. Murali, M. Posselt, S. V. M. Satyanarayana

摘要:

BaZrO 3具有优异的质子传导性和良好的高温稳定性。因此,它是一种很有前途的固体氧化物燃料电池电解质材料。BaZrO 3在高温下的稳定性通常由O空位的低扩散率来解释。目前的第一性原理密度泛函理论计算表明,在高温下的双正电荷的O空位的缓慢迁移不能单独由基态迁移能,而是由声子激发的自由迁移能的贡献。随着温度的升高,氧空位迁移的有效势垒增加。在燃料电池的工作温度约1000 K时,计算的O空位扩散率比仅使用基态迁移势垒确定的扩散率低一个数量级以上。计算的扩散系数数据与文献中的实验结果吻合得很好。研究表明,BaZrO_3的高温稳定性主要是由于声子对O空位自由迁移能的贡献。

英文摘要:

BaZrO3 exhibits excellent proton conductivity and good high-temperature stability. It is therefore a promising electrolyte material for solid oxide fuel cells. The stability of BaZrO3 at high temperatures is generally explained by the low diffusivity of the O vacancy. Present first-principle Density-Functional-Theory calculations show that the slow migration of the doubly positively charged O vacancy at high temperature cannot be solely caused by the ground-state migration energy but by the contribution of phonon excitations to the free migration energy. With increasing temperature, the effective barrier for oxygen vacancy migration increases. At about 1000K, which is the operating temperature of fuel cells, the calculated O vacancy diffusivity is more than one order of magnitude lower than that determined using solely the ground-state migration barrier. The calculated diffusivity data agree well with experimental results from literature. The present work reveals that the high-temperature stability of BaZrO3 is mainly due to the phonon contribution to the free migration energy of the O vacancy.

机构、总结、中文摘要均由AI分析而来,可能存在错误,请以论文正文为准。

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