title: Enhancing grain boundary ionic conductivity in mixed ionic-electronic conductors.
abstract: 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.
authors: Department of Mechanical Engineering, University of South Carolina, Columbia, South Carolina 29208, USA.
authors: Ye
authors: Y
authors: Lin
authors: Department of Mechanical Engineering, University of South Carolina, Columbia, South Carolina 29208, USA.
authors: Shumin
authors: S
authors: Fang
authors: Center for Functional Nanomaterials, Brookhaven National Laboratory, Upton, New York 11973, USA.
authors: Dong
authors: 0000000219216683
authors: D
authors: Su
authors: Department of Materials Science and Engineering, Clemson University, Clemson, South Carolina 29634, USA.
authors: Kyle S
authors: KS
authors: Brinkman
authors: Department of Mechanical Engineering, University of South Carolina, Columbia, South Carolina 29208, USA.
authors: Fanglin
authors: 0000000199428872
authors: F
authors: Chen