Kuang Xiaojun, Green Mark A, Niu Hongjun, Zajdel Pawel, Dickinson Calum, Claridge John B, Jantsky Laurent, Rosseinsky Matthew J
Department of Chemistry, The University of Liverpool, Liverpool, L69 7ZD, UK.
Nat Mater. 2008 Jun;7(6):498-504. doi: 10.1038/nmat2201. Epub 2008 May 18.
High-conductivity oxide ion electrolytes are needed to reduce the operating temperature of solid-oxide fuel cells. Oxide mobility in solids is associated with defects. Although anion vacancies are the charge carriers in most cases, excess (interstitial) oxide anions give high conductivities in isolated polyhedral anion structures such as the apatites. The development of new families of interstitial oxide conductors with less restrictive structural constraints requires an understanding of the mechanisms enabling both incorporation and mobility of the excess oxide. Here, we show how the two-dimensionally connected tetrahedral gallium oxide network in the melilite structure La(1.54)Sr(0.46)Ga(3)O(7.27) stabilizes oxygen interstitials by local relaxation around them, affording an oxide ion conductivity of 0.02-0.1 S cm(-1) over the 600-900 degrees C temperature range. Polyhedral frameworks with central elements exhibiting variable coordination number can have the flexibility needed to accommodate mobile interstitial oxide ions if non-bridging oxides are present to favour cooperative network distortions.
需要高电导率的氧化物离子电解质来降低固体氧化物燃料电池的工作温度。固体中的氧化物迁移率与缺陷有关。虽然在大多数情况下阴离子空位是电荷载流子，但在诸如磷灰石等孤立的多面体阴离子结构中，过量（间隙）氧化物阴离子具有高电导率。开发具有较少限制性结构约束的新型间隙氧化物导体家族需要了解使过量氧化物能够掺入和迁移的机制。在这里，我们展示了钙铝黄长石结构La(1.54)Sr(0.46)Ga(3)O(7.27)中二维连接的四面体氧化镓网络如何通过其周围的局部弛豫来稳定氧间隙，在600 - 900摄氏度的温度范围内提供0.02 - 0.1 S cm(-1)的氧化物离子电导率。如果存在非桥连氧化物以促进协同网络畸变，具有中心元素呈现可变配位数的多面体框架可以具有容纳可移动间隙氧化物离子所需的灵活性。
