Optimization of Material Contrast for Efficient FIB‐SEM Tomography of Solid Oxide Fuel Cells

Focused ion beam (FIB) – scanning electron microscopy (SEM) serial sectioning tomography has become an important tool for three‐dimensional microstructure reconstruction of solid oxide fuel cells (SOFC) to obtain an understanding of fabrication‐related effects and SOFC performance. By sequential FIB milling and SEM imaging a stack of cross‐section images across all functional SOFC layers was generated covering a large volume of 3.5·10$^{4}$ μm$^{3}$. One crucial step is image segmentation where regions with different image intensities are assigned to different material phases within the SOFC. To analyze all relevant SOFC materials, it was up to now mandatory to acquire several images by scanning the same region with different imaging parameters because sufficient material contrast could otherwise not be achieved. In this work we obtained high‐contast SEM images from a single scan to reconstract all functional SOFC layers consisting of a Ni/Y$_{2}$O$_{3}$‐doped ZrO$_{2}$ (YDZ) cermet anode, YDZ electrolyte and (La,Sr)MnO$_{3}$/YDZ cathode. This was possible by using different, simultaneous read‐out detectors installed in a state‐of‐the‐art scanning electron microscope. In addition, we used a deterministic approach for the optimization of imaging parameters by employing Monte Carlo simulations rather than trial‐and‐error tests. We also studied the effect of detection geometry, detecting angle range and detector type

Investigation of LSM/8YSZ cathode within an all-ceramic SOFC, Part II: Optimization of performance and co-sinterability

This paper focuses on the cathode and current collector layers of a co-sintered, all-ceramic solid oxide fuel cell (SOFC) concept. Challenges to reach good electrochemical performance have to be overcome, due to more demanding manufacturing conditions, including a relatively high co-sintering temperature. Master sintering curves show that the sintering activity of lanthanum strontium manganite (LSM) is significantly higher than that of 8-mol% yttria stabilized zirconia (8YSZ). By applying a double-layered cathode and a current collector with optimized microstructures the best electrochemical performance of the cathode is 0.26 cm at 800 C, evaluated from polarization resistances of 8YSZ electrolyte-supported symmetric cells post-sintered at 1150 C  C. The cathode and current collector materials are adapted to fit the co-sintering process by adjustment of the paste compositions. Half-cells consisting of silicate mechanical support, LSM current collector, LSM mixed with 8YSZ composite cathode and 8YSZ electrolyte are co-sintered porous and defect-free at 1150 C  C

Effects of Grain Boundary Decoration on the Electrical Conduction of Nanocrystalline CeO2

In this study, we investigate the effect of decorating the grain boundaries of nanocrystalline undoped ceria on the electrical transport properties. For the decoration, different acceptors (Yb, Y, Bi) were chosen. On decoration, the conduction switches from electronic to ionic. Upon sintering the grains are characterized by a core-shell configuration, in which the core remains undoped while the shell is heavily doped as a consequence of the diffusion of the acceptors toward the grain interior. The shell dominates the overall transport properties of the nanocrystalline ceria and is found to be in the mesoscopic regime