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The Tennessee Technological University (TTU) will develop and demonstrate a cobalt-free nickel iron oxide [Co-free (Ni,Fe)3O4] spinel for solid oxide fuel cell (SOFC) cathode-side contact application using an environmentally-assisted reactive sintering (EARS) process at a lower sintering temperature. The starting powders and EARS parameters for the (Ni,Fe)3O4 spinel layer formation will be studied and optimized. The EARS mechanism for the spinel formation in air will be elucidated using metallic starting powders. Researchers will assess the area-specific resistance (ASR) of the developed contact layers under isothermal and cyclic exposure conditions as well as their chemical compatibility and chromium-retaining capability. Approaches to further improve the performance of the (Ni,Fe)3O4 spinel contact—such as doping the spinel with other transition metals, adding a suitable perovskite to form a composite contact material, etc.—will also be explored. A cost analysis will detail the cost reduction in both materials (e.g., utilizing a Co-free spinel phase) and processing (e.g., lowering the sintering temperature via exothermic reactions).
TTU’s deposition of the metallic precursor layers via low-cost processes as well as in-situ sintering of the spinel-containing layer at the SOFC stack startup temperature enables development of the Co-free spinel contact structure at a significant reduction in overall cost. This spinel contact structure is expected to provide improved performance compared to the current contact materials because of its good electrical conductivity, adequate coefficient of thermal expansion, excellent chromium-retaining capability, and chemical compatibility to the different components. A new spinel-based structure between the cathode and interconnect will also help improve the robustness/reliability/endurance of SOFC stacks, thus contributing to the commercial viability of the SOFC technology.
