Characterization of 3D interconnected microstructural network in mixed ionic and electronic conducting ceramic composites

Abstract

The microstructure and connectivity of the ionic and electronic conductive phases in composite ceramic membranes are directly related to device performance. Transmission electron microscopy (TEM) including chemical mapping combined with X-ray nanotomography (XNT) have been used to characterize the composition and 3-D microstructure of a MIEC composite model system consisting of a Ce 0.8 Gd 0.2 O 2 (GDC) oxygen ion conductive phase and a CoFe 2 O 4 (CFO) electronic conductive phase. The microstructural data is discussed, including the composition and distribution of an emergent phase which takes the form of isolated and distinct regions. Performance implications are considered with regards to the design of new material systems which evolve under non-equilibrium operating conditions.

An Interdisciplinary View of Interfaces: Perspectives Regarding Emergent Phase Formation

“…7 (a) Orthographic revealing the 3D structure of CGO-CFO systems [60]. (Reproduced with permission from Harris et al [60]. Copyright 2014 by Nanoscale Owner Societies) (b) 3D representation of varying Cs content observed in single-phase hollandite Ba 1 [82].…”

“…Fig. 7 (a) Orthographic revealing the 3D structure of CGO-CFO systems [60]. (Reproduced with permission from Harris et al [60].…”

“…At the mesoscale, X-ray nanotomography has been utilized to characterize the composition and 3D microstructure of the MIEC CGO oxygen ion conductive phase and a CFO electronic conductive phase, revealing the spatial distribution of the GFCCO "emergent" phases as shown in Fig. 7 [60]. Focused ion beam-scanning electron microscopy serial sectioning has become well established for 3D imaging of multiphase materials with energy applications including solid oxide fuel cell materials and can also incorporate element-sensitive imaging through the use of backscatter electron imaging or energy-dispersive X-ray spectroscopy methods [81].…”

“…However, the performance of DP-MIECs is not necessarily controlled by the properties of individual constituents. Phase interactions and altered interfaces such as grain boundaries play a role in determining the overall performance [31,59,60].…”

Is 2D stereological method good enough for quantification of solid oxide fuel cell electrode microstructure?

“…However, the quantification of SOFC electrode microstructures is a longstanding project due to the extreme complexity in threedimensions (3D). In recent years, focused ion beam-scanning electron microscopy (FIB-SEM) and X-ray computed tomography (XCT) techniques have been used to reconstruct the 3D microstructures of the porous electrodes [4][5][6], so that the geometric factors, such as porosity, connectivity, three-phase boundary (TPB) length, and inner surface areas can be accurately obtained. The 3D microstructures can be used as the framework for modeling electrochemical and heat-mass transfer processes without using empirical idealizations in microstructures, and thus set up a quantitative linkage between performance and microstructure [7].…”