•The growth of the oxide scale thickness is influenced by electric current.•The oxidation rates vary greatly depending on its local environment.•The value of ASR depends on the composition and thickness of oxide layer.Oxidation behavior of integrated interconnect with bipolar plate and corrugated sheet made by ferrite steel SUS430 is investigated and compared in simulated environment and in a realistic stack. Electrical current is found to have a direction-related impact on the thickness of the Cr2O3/MnCr2O4 composite oxide scale. Oxide scale of the interconnect aged in the stack exhibits a dual-layered structure of a complex Mn-Cr oxide layer covered by iron oxide. The oxidation rates vary greatly depending on its local environment, with different thermal, electrical density, as well as gas composition conditions. By analyzing the thickness distribution of oxide scale and comparing them with the simulated test result, the oxidation behavior of interconnect in stack is described in high definition. ASR distribution is also conducted by calculation, which could help further understanding the behavior of stack degradation.

•Single phase La0.9M0.1NbO4 (M = Sm, Gd, Yb) was prepared and the crystal structure was investigated.•Electrical properties of La0.9M0.1NbO4 (M = Sm, Gd, Yb) were characterized.•Taking Sm, Gd, or Yb as a substitute could improve the electrical conductivity of LaNbO4 by orders.In LaNbO4, Sm, Gd and Yb were investigated as substitutes to enhance its ion conductivity, for its application in solid oxide fuel cell. La0.9M0.1NbO4 (M = Sm, Gd, Yb) was prepared via a solid–state reaction route and single phase was attained by calcining the constituent oxides at 1200 °C for 5 h. The total conductivity of LaNbO4 was increased by partly replaced La with Sm, Gd and Yb, due to the muti-valences of the substitutions. The highest conductivity (1.76 × 10−4 S cm−1) was achieved for La0.9Sm0.1NbO4 at 800 °C in wet air, more than one order higher compared to that of LaNbO4. The introduction of Sm, Gd or Yb also slightly increased the ion transport number of LaNbO4, indicating that the increase of the total conductivity was mainly contributed by the enhanced ion conductivity, which was beneficial for its application as a pure ion conductor.

•A novel micro structure configuration of cathode contact layer was designed.•The structure of combined coarse and fine particles improves thermal cycle stability.•The new structure tested in a 1-cell stack showed high performance and durability.A novel structure layer of the cathode contact materials LaCo0.6Ni0.4O3−δ (LCN) containing fine particles layer and coarse particles layer is designed to compare with the conventional structure layer in the condition of thermal cycle from 200 °C to 750 °C. The thermal expansion measurements of LCN in different particle sizes are investigated to explore the strength matching about the thermal expansion coefficient (TEC) and sintering shrink between them and interconnect. For the novel structure of LCN layer, with a ferritic stainless steels SUS430 as the interconnect, the area specific resistance (ASR) of SUS430/LCN/SUS430 increase to 110 mΩ cm2 in 15 thermal cycles and remains stable in the following thermal cycles. The formation of the oxide scale on the surface of SUS430 which is negligible to the measured ASR depends on the oxygen partial pressure on the interface. With the novel structure of LCN as the cathode contact layer, the power density above 390 mW cm−2 is obtained at 750 °C at a current density of 500 mA cm−2 and the average degradation rate is 0.4% per cycle in the following thermal cycle test and the degradation tends to more stable with the times of thermal cycle increase.

•Performance degradation was related with surface chemistry for LSCF–SDC cathodes.•Performance degradation was mainly caused by low frequency mass transfer process.•Sr segregation on the surface was suppressed by lowering oxygen partial pressure.The stability and surface composition of La0.6Sr0.4Co0.2Fe0.8O3 − δ (LSCF)–Sm0.2Ce0.8O2 (SDC) cathodes prepared by impregnation are investigated at 750 °C under open circuit and different oxygen partial pressures. The performance degradation during the test at Po2 = 0.21 atm is closely related to the low frequency mass transfer process. Little change of the electrochemical performance of cathodes is observed after 24 h test at Po2 = 0.001 atm. XPS patterns show that the decrease in oxygen partial pressure leads to the suppression of Sr enrichment on the surface of cathodes and retards the performance degradation.

•La1 − xZnxNbO4 − δ with various Zn contents was prepared; phase and sintered microstructure were characterized.•The effect of composition and microstructure on conductivity was evaluated.•The total conductivity of LaNbO4 was improved obviously by Zn doping.Zn-doped LaNbO4 (La1 − xZnxNbO4 − δ, LZ100x) was prepared by a solid-state reaction method with x = 0, 0.005, 0.01, 0.015, 0.03 and 0.05 and investigated by X-ray diffraction (XRD), transmission electron microscopy (TEM), scanning electron microscopy (SEM) and conductivity measurement. There were no XRD and TEM evidences of formed secondary phases in the composition range of x ≤ 0.03 due to the sensitivity. However, the solubility of Zn, less than 1.0 mol.%, was reasonable, according the variety of the grain sizes, conductivity, as well as the activation energy for the conductivity, with the increasing concentration of Zn. The conductivity of LaNbO4 was improved by one to two orders of magnitude with Zn doping in the research range; and the highest conductivity of 9.8 × 10− 4 S cm− 1 was obtained with LZ0.5 at 900 °C in wet air.

•Metal support SOFC was prepared by tape casting and screen printing technique.•The cell exhibited excellent performance at low operation temperature.•There is no significant degradation after five of redox recycles of the cell.Novel Ni–Fe alloy supported solid oxide fuel cells, with Ni cermet as functional anode, La0.8Sr0.2MnO3 coated Ba0.5Sr0.5Co0.2Fe0.8O3 as cathode and Gd-doped Ce2O3 as electrolyte, are successfully fabricated by the cost effective method of tape casting-screen printing-cofiring. The Ni–Fe porous substrate is obtained by reduction (in H2 at 650 °C for 2 h) of sintered NiO-10 wt% Fe2O3 consisting of NiO and NiFe2O4. The cell is subjected to evaluation in the aspects of electrochemical performance and redox capability at temperatures between 500 and 650 °C. The result shows a peak power density of 1.04 W cm−2 at 650 °C. Furthermore, the metal support cell exhibits excellent tolerance to redox cycles. Five redox recycles for cells are operated at 600 °C, which shows no significant degradation in open circuit voltage and power density.