Department of Materials Science and Engineering, University of Sheffield, Sir Robert Hadfield Building, Mappin Street, Sheffield S1 3JD, UK.
Institute of Physical Chemistry, RWTH Aachen University and JARA-FIT, D-52056 Aachen, Germany.
Nat Mater. 2014 Jan;13(1):31-5. doi: 10.1038/nmat3782. Epub 2013 Nov 10.
Oxide ion conductors find important technical applications in electrochemical devices such as solid-oxide fuel cells (SOFCs), oxygen separation membranes and sensors. Na0.5Bi0.5TiO3 (NBT) is a well-known lead-free piezoelectric material; however, it is often reported to possess high leakage conductivity that is problematic for its piezo- and ferroelectric applications. Here we report this high leakage to be oxide ion conduction due to Bi-deficiency and oxygen vacancies induced during materials processing. Mg-doping on the Ti-site increases the ionic conductivity to ~0.01 S cm(-1) at 600 °C, improves the electrolyte stability in reducing atmospheres and lowers the sintering temperature. This study not only demonstrates how to adjust the nominal NBT composition for dielectric-based applications, but also, more importantly, gives NBT-based materials an unexpected role as a completely new family of oxide ion conductors with potential applications in intermediate-temperature SOFCs and opens up a new direction to design oxide ion conductors in perovskite oxides.
氧化物离子导体在电化学装置中有着重要的技术应用，如固体氧化物燃料电池（SOFCs）、氧分离膜和传感器。Na0.5Bi0.5TiO3（NBT）是一种知名的无铅压电材料；然而，据报道它通常具有较高的漏导，这对其压电和铁电应用是有问题的。在这里，我们将这种高漏导归因于材料处理过程中产生的 Bi 缺乏和氧空位引起的氧化物离子传导。Ti 位的 Mg 掺杂使离子电导率在 600°C 时提高到约 0.01 S cm(-1)，改善了在还原气氛中的电解质稳定性并降低了烧结温度。这项研究不仅展示了如何调整基于介电的应用的 NBT 名义组成，而且更重要的是，赋予了基于 NBT 的材料作为一类全新的氧化物离子导体的意想不到的作用，在中温 SOFC 中有潜在的应用，并为钙钛矿氧化物中氧化物离子导体的设计开辟了新的方向。
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