Lin Ye, Fang Shumin, Su Dong, Brinkman Kyle S, Chen Fanglin
Department of Mechanical Engineering, University of South Carolina, Columbia, South Carolina 29208, USA.
Center for Functional Nanomaterials, Brookhaven National Laboratory, Upton, New York 11973, USA.
Nat Commun. 2015 Apr 10;6:6824. doi: 10.1038/ncomms7824.
Mixed ionic-electronic conductors are widely used in devices for energy conversion and storage. Grain boundaries in these materials have nanoscale spatial dimensions, which can generate substantial resistance to ionic transport due to dopant segregation. Here, we report the concept of targeted phase formation in a Ce0.8Gd0.2O2-δ-CoFe2O4 composite that serves to enhance the grain boundary ionic conductivity. Using transmission electron microscopy and spectroscopy approaches, we probe the grain boundary charge distribution and chemical environments altered by the phase reaction between the two constituents. The formation of an emergent phase successfully avoids segregation of the Gd dopant and depletion of oxygen vacancies at the Ce0.8Gd0.2O2-δ-Ce0.8Gd0.2O2-δ grain boundary. This results in superior grain boundary ionic conductivity as demonstrated by the enhanced oxygen permeation flux. This work illustrates the control of mesoscale level transport properties in mixed ionic-electronic conductor composites through processing induced modifications of the grain boundary defect distribution.
混合离子电子导体广泛应用于能量转换和存储设备中。这些材料中的晶界具有纳米级空间尺寸，由于掺杂剂偏析，会对离子传输产生显著阻力。在此，我们报道了一种用于增强晶界离子电导率的Ce0.8Gd0.2O2-δ-CoFe2O4复合材料中的定向相形成概念。利用透射电子显微镜和光谱学方法，我们探测了由两种成分之间的相反应改变的晶界电荷分布和化学环境。新相的形成成功避免了Gd掺杂剂在Ce0.8Gd0.2O2-δ-Ce0.8Gd0.2O2-δ晶界处的偏析以及氧空位的耗尽。如增强的氧渗透通量所示，这导致了优异的晶界离子电导率。这项工作说明了通过加工诱导的晶界缺陷分布改性来控制混合离子电子导体复合材料中的中尺度传输特性。
