Ba₇Nb₄MoO₂₀ exhibits excellent oxygen ion transport properties and is a promising electrolyte material for solid oxide fuel cell (SOFC). To further enhance its oxygen ionic conductivity, element doping is an effective strategy. However, few studies have delved into the impact mechanism of doping strategies on the electrolyte's conductivity properties from the perspective of electronic structure. Here, the enhancement mechanism of oxygen ionic conductivity in Ba₇Nb₄MoO₂₀ was analyzed using the the methods of density of states (DOS) and Crystal Orbital Hamilton Populations (COHP). Since the electronic conductivities of the electrolytes are negligible, their total conductivies can essentially be regarded as the conductivies of oxygen ions. As the Sr doping amount increases, the oxygen ionic conductivities of the electrolytes also increase. The bulk conductivity shows a negative correlation with the Sr doping amount, which is due to the higher bond energy of Sr-O compared to Ba-O. On the other hand, Sr promotes grain growth and reduces the number of grain boundaries, thereby decreasing the resistance to oxygen diffusion at the grain boundaries and thus enhancing the grain boundary conductivity. In the Ba_7-xSr_xNb₄MoO_20-δ (x=0, 0.1, 0.2, 0.3, and 0.4) perovskite oxides, Ba_6.6Sr_0.4Nb₄MoO_20-δ has the highest conductivity, reaching 1.12 × 10^-4S cm^-1 at 500°C. This work not only develops a SOFC electrolyte material with promising application prospects, but also provides theoretical guidance for its doping modification.

中文翻译：

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Sr2+掺杂对六方钙钛矿Ba7-xSrxNb4MoO20-δ电解液结构和电学性能的影响：实验和DFT建模研究


Ba₇Nb₄MoO₂₀ 表现出优异的氧离子传输性能，是一种很有前途的固体氧化物燃料电池 （SOFC） 电解质材料。为了进一步提高其氧离子电导率，元素掺杂是一种有效的策略。然而，很少有研究从电子结构的角度深入研究掺杂策略对电解质导电性能的影响机制。在这里，使用状态密度 （DOS） 和晶体轨道汉密尔顿群 （COHP） 的方法分析了 Ba₇Nb₄MoO₂₀ 中氧离子电导率的增强机制。由于电解质的电子电导率可以忽略不计，因此它们的总电导率基本上可以看作是氧离子的电导率。随着 Sr 掺杂量的增加，电解质的氧离子电导率也增加。体电导率与 Sr 掺杂量呈负相关，这是因为与 Ba-O 相比，Sr-O 的键能更高。另一方面，Sr 促进晶粒生长并减少晶界的数量，从而降低晶界对氧扩散的阻力，从而增强晶界电导率。在 Ba_7-x Sr_xNb₄MoO_20-δ（x=0、0.1、0.2、0.3 和 0.4）钙钛矿氧化物中，Ba_6.6Sr_0.4Nb₄MoO_20-δ 具有最高的电导率，在 500°C 时达到 1.12 × ^10-4S ^cm-1。 这项工作不仅开发了一种具有良好应用前景的 SOFC 电解质材料，而且为其掺杂改性提供了理论指导。