(La0.8Sr0.2)MnO3-Ni composite for the interconnect of solid oxide cells: effect of starting Ni particle size on sintering and electrical properties

This study demonstrates the feasibility of applying La0.8Sr0.2MnO3 (LSM)-Ni oxide-metal composite to an interconnect layer for anode-supported solid oxide cells (SOCs) operated at 700 °C. The sintering behavior of LSM-Ni composites and the electrical properties of LSM-Ni composite in both reducing and oxidizing atmospheres were systematically examined. The densification and final microstructure of LSM-Ni composites are tailored by varying the size and content of Ni particles. A part of smaller Ni particles reacts with LSM matrix and forms a second phase, Sr-doped La2NiO4. The addition of Sr to La2NiO4 decreases the melting temperature of La2NiO4, which causes the liquid phase sintering and increases the density of the sintered of LSM-Ni composites. It is also found that LSM-Ni composites are electrically conductive, regardless of the atmosphere. In oxidizing atmospheres, LSM perovskite serves as the major conductive matrix. In reducing atmospheres, on the other hand, embedded Ni forms metallic percolation path and compensates for the decrease in the electrical conductivity of reduced LSM ceramics. This LSM-Ni is used to coat the multilayer thick film of LSM-Ni and LSM. The multilayer film exhibits higher and more stable electric conductivity than the single layer thick film of LSM in a simulated SOC operation environment. This shows that LSM-Ni composite can be a useful component of the interconnect of SOC, which maintains the good electric conductivity in both air and H2.