Ni and metal aluminate mixtures for solid oxide fuel cell anode supports

Mixtures of nickel and metal aluminate (Ni–MAl₂O₄ [M = Fe, Co, Ni and Cu]) were fabricated, and their electrical conductivities, microstructures and thermal expansions were measured. During the sintering of these mixtures, MAl₂O₄ reacts with NiO to form NiAl₂O₄ and MO_x which are thought to be the reasons for the differences in the microstructures and electrical properties. Except for FeAl₂O₄, Ni–MAl₂O₄ mixtures show metallic conductivity behavior and their electrical conductivities are sufficient for cell operation. Their thermal expansion coefficients are much lower than conventional Ni-YSZ mixtures and closer to the 8YSZ electrolyte. The peak power densities of single cells supported with Ni–NiAl₂O₄ and Ni–CoAl₂O₄ are 410 and 440 mW cm⁻² at 850 °C, respectively, which are lower than 490 mW cm⁻² of Ni-YSZ. This is due to the polarization resistances of functional anode layer. The Ni–CuAl₂O₄-supported cell has no electrical performance because of Cu migration and segregation.