| Silver-perovskite composites with the perovskite being either (La 0.6Sr0.4)(Co0.8Fe0.2)O3 (LSCF) or La0.8Sr0.2MnO3 (LSM) were evaluated as the contact material between the ferritic interconnect alloy Crofer 22 APU and the LSM cathode. The area specific resistances (ASR's) and the Cr-blocking abilities of the specimens were highly dependent on the type and volume percentage of the perovskite present in the composite and the amount of thermal cycling that the cells underwent. Replacement of Ag in the composite with other noble metals, such as Au, Pt, and Pd, showed similar behavior. Lanthanum-doped strontium titanate (LST) and a cobalt-plated layer were evaluated in the anode environment as the anode-interconnect contact and solid-state diffusion barrier, respectively. The ASR of the LST contact was shown to be highly dependent on the size of the particles within the contact layer. Cobalt plating was not detrimental to the solid-state diffusion behavior of Crofer 22 APU, and the extent of diffusion was found to be dependent on the method for attaching the nickel mesh to the ferritic interconnect. Silver-perovskite composite contact materials are promising candidates for use in intermediate temperature SOFC stacks with ferritic stainless steel interconnects due to their ability to maintain acceptably low ASR's while reducing Cr migration into the cathode material. LST-based contact materials show potential for use at the anode-interconnect interface, while the presence of the cobalt-plated layer on ferritic steels might reduce the interdiffusion between the interconnect and Ni-based contact material on the anode side. |
