A metal-supported solid oxide fuel cell (SOFC) using Ce0.8Sm0.2O2 (Sm-doped ceria, SDC) buffer layer and La0.9Sr0.1Ga0.8Mg0.2O3 (LSGM) electrolyte films showed a small degradation in the cell performance after a long-term operation because of La migration from the electrolyte to the buffer layer, resulted in a formation of a less conductive phase. Thus, various ceramic materials such as doped ceria and perovskite-related oxides were investigated for an effective buffer layer with respect to fabricating reliable metal-supported SOFCs using a LSGM electrolyte film. In particular, La-doped CeO2 (LDC) and Pr-doped LaCrO3 (LPCr) were investigated as buffer layer material since the materials showed chemical compatibility with the LSGM and anode materials. The cell using a LDC buffer layer showed a prior stability during the operation for 100 h at 973 K, while the power density of the cell was slightly low owing to the low electrical conductivity of LDC compared with that of SDC or LPCr. In contrast, the cell using a LPCr buffer layer revealed significantly low open circuit voltage (OCV) and power density, which were attributed to Pr decomposition in the LPCr caused by the reactivity with water vapor. However, the metal-supported cell with a multilayer electrolyte film including LSGM/LPCr/SDC layers showed an almost theoretical OCV and reasonably high power density with no degradation after a long-term operation for 100 h at 973 K, suggesting that the LPCr layer effectively prevented La migration and the SDC layer led to avoid the Pr decomposition. Thus, a LPCr is an effective buffer layer material for reliable metal-supported SOFCs using a LSGM electrolyte thin film.

Redox reactions were studied at a single yttria-stabilized zirconia (YSZ)/Pt electrode interface, in parallel with pure YSZ with no catalyst electrode, by in situ analytical electron microscopy at elevated temperatures and in an oxygen atmosphere. In situ electron holography showed that the oxide underwent reduction at elevated temperatures in a vacuum and was consequently reoxidized upon exposure to an oxygen flux at the same temperature. In situ energy loss spectroscopy measurements were in agreement with in situ electron holography observations and indicated that the oxidation state of the host cation zirconium was altered in the reduced state of the YSZ to the metastable state Zr3+.

In situ X-ray diffraction was used to study the interactions of the PNNL G18 fuel cell sealing glasses with the oxides that form on candidate interconnect alloys and with the ebrite alloy. Experiments under 4% hydrogen and air at temperatures up to 1000 °C showed that the sealant reacts rapidly with alumina and chromia, but not with NiO. The crystallization of the high-CTE phase BaCrO4 was noted for G18 in contact with chromia or ebrite under air, but reducing conditions inhibit the crystallization. The reactions in all cases begin within a few hours at temperatures above 800 °C and go to completion or near completion after ∼12 h.

Microstructural evolution in a CeO2-Gd2O3 system at atomic and nanoscale levels with increasing Gd concentration has been comprehensively investigated by transmission electron microscopy. When the Gd concentration was increased from 10 to 80 at.%, the phase transformation from ceria with fluorite structure to solid solution with C-type structure was not a sudden change but an evolution in the sequence of clusters, domains, and precipitates with C-type structure in the fluorite-structured matrix. Moreover, the ordering of aggregated Gd cations and oxygen vacancies in these microstructural inhomogeneities developed continuously with increasing Gd concentration. This microstructural evolution can be further described based on the development of defect clusters containing Gd cations and oxygen vacancies.

Nanosized incubational domain was observed in 10 at.% gadolinium-doped ceria (GDC) using high-resolution transmission electron microscopy. Dislocations were extensively observed in 10 at.% GDC instead of heavily doped 25 at.% GDC. By Fast Fourier Transform and Inverse Fast Fourier Transform analysis, it was noticed that the incubational domain existing in 10 at.% GDC has different lattice spacing and orientation from the neighboring ceria matrix. Furthermore, dislocations were usually observed in the interface region between the incubational domain and the ceria matrix. Based on experimental results, the formation mechanism of dislocation associated incubational domain in lightly gadolinium-doped ceria is rationalized.