Composition, crystallography, and oxygen vacancy ordering impacts on the oxygen ion conductivity of lanthanum strontium ferrite
Composition, crystallography, and oxygen vacancy ordering impacts on the oxygen ion conductivity of lanthanum strontium ferrite
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DOI：
10.1039/d0cp00206b
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发表时间：
2020-05-07
影响因子：
3.3
通讯作者：
Qi, Yue
中科院分区：
文献类型：
--
作者：
Das, Tridip;Nicholas, Jason D.;Qi, Yue
这项工作提出了一个全面的计算研究，显示了共价掺杂，晶体结构和氧空位相互作用如何影响镧锶铁氧体（LSF）的氧空位电导率作为空气温度的函数。首先，通过密度泛函理论（DFT）计算得到氧空位迁移势垒，了解氧空位迁移过程中邻近铁原子的氧化态变化。然后，将氧迁移势垒能和相应的扩散系数与先前确定的移动氧空位浓度相结合，预测总体氧空位电导率，并将其与实验测量值进行比较。更重要的是，分析了相变、La/Sr比和氧非化学计量对移动氧空位浓度、扩散系数和电导率的影响。研究发现，稳定菱面体LSF或立方SFO（通过掺杂或其他方法）可以防止氧空位有序引起的相变，从而在固体氧化物燃料电池工作条件下获得高氧电导率。
This work presents a comprehensive computational study showing how aliovalent doping, crystal structure, and oxygen vacancy interactions impact the oxygen vacancy conductivity of lanthanum strontium ferrite (LSF) as a function of temperature in air. First, density functional theory (DFT) calculations were performed to obtain the oxygen vacancy migration barriers and understand the oxidation state changes on neighboring Fe atoms during oxygen vacancy migration. The oxygen migration barrier energy and the corresponding diffusion coefficient were then combined with previously determined mobile oxygen vacancy concentrations to predict the overall oxygen vacancy conductivity and compare it with experimentally measured values. More importantly, the impact of phase changes, the La/Sr ratio, and the oxygen non-stoichiometry on the mobile oxygen vacancy concentration, diffusivity, and conductivity were analyzed. It was found that stabilizing rhombohedral LSF or cubic SFO (through doping or other means), such that oxygen-vacancy-ordering-induced phase transitions are prevented, leads to high oxygen conductivity under solid oxide fuel cell operating conditions.