Oxide-Ion Occupational Disorder, Diffusion Path, and Conductivity in Hexagonal Perovskite Derivatives Ba3WNbO8.5 and Ba3MoNbO8.5
Oxide-Ion Occupational Disorder, Diffusion Path, and Conductivity in Hexagonal Perovskite Derivatives Ba3WNbO8.5 and Ba3MoNbO8.5
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六方钙钛矿衍生物 Ba3WNbO8.5 和 Ba3MoNbO8.5 中的氧离子职业障碍、扩散路径和电导率
DOI：
10.1021/acs.jpcc.1c09416
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发表时间：
2022
期刊：
影响因子：
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通讯作者：
Yashima Masatomo
中科院分区：
文献类型：
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作者：
Yasui Yuta;Tsujiguchi Takafumi;Sakuda Yuichi;Hester James R.;Yashima Masatomo
六方钙钛矿衍生物Ba3MNbO8.5（M：W和Mo）由于高氧化物离子电导率和在许多应用中的潜在用途而引起了人们的广泛兴趣。这项工作显示了 Ba3WNbO8.5(3.7 × 10–2S cm–1) 和 Ba3MoNbO8.5(8.8 × 10–2S cm–1) 在 900 °C 时的电导率，并证实 Ba3WNbO8.5 的电导率活化能高于 Ba3MoNbO8.5。控制电导率和活化能的关键因素是四面体 O3 与八面体 O2 氧化物离子的比率以及 Ba3MNbO8.5 中的扩散路径。然而，O2/O3 紊乱和氧化物离子扩散路径是 Ba3MNbO8.5 中尚未解决的重要问题。在这里，对高达 800 °C 的原位中子衍射数据进行 Rietveld 和最大熵法 (MEM) 分析，以获得 Ba3WNbO8.5 的晶体结构和中子散射长度密度 (NSLD)。 MEM NSLD 显示出二维氧离子迁移穿过本质缺氧层中的八面体 O2 和四面体 O3 位点。随着温度的升高，间隙O3和晶格O2原子n(O3)和n(O2)的数量分别增加和减少，这表明O2/O3无序在高温下更加突出。 O2/O3 无序化使得 O2-O3 路径上的最小 NSLD 更高，从而增强了氧化物离子电导率，导致 Ba3WNbO8.5 与 Ba3MoNbO8.5 相比具有更高的活化能。
Hexagonal perovskite derivatives Ba3MNbO8.5(M: W and Mo) are attracting much interest due to high oxide-ion conductivity and potential use for many applications. This work shows the electrical conductivities of Ba3WNbO8.5(3.7 × 10–2S cm–1) and Ba3MoNbO8.5(8.8 × 10–2S cm–1) at 900 °C and confirms higher activation energy for conductivity of Ba3WNbO8.5than that of Ba3MoNbO8.5. Key factors governing the conductivity and activation energy are the ratio of tetrahedral O3 to octahedral O2 oxide ions and diffusion pathways in Ba3MNbO8.5. However, the O2/O3 disorders and oxide-ion diffusion paths are unresolved important issues in Ba3MNbO8.5. Here, Rietveld and maximum-entropy method (MEM) analyses ofin situneutron-diffraction data up to 800 °C were performed to obtain the crystal structure and neutron scattering length densities (NSLDs) of Ba3WNbO8.5. MEM NSLDs show two-dimensional oxide-ion migration through the octahedral O2 and tetrahedral O3 sites in the intrinsically oxygen-deficient layer. Numbers of the interstitial O3 and lattice O2 atomsn(O3) andn(O2) increase and decrease, respectively, with increasing temperature, which indicates that the O2/O3 disorder is more prominent at high temperatures. The O2/O3 disordering makes the minimum NSLD on the O2–O3 path higher, which enhances oxide-ion conductivity, leading to higher activation energies of Ba3WNbO8.5compared with Ba3MoNbO8.5.