Effects of La0.67Sr0.33MnO3 protective coating on SOFC interconnect by plasma-sputtering

Two metallic alloys, namely, Crofer22 APU and equivalent ZMG23 were investigated as possible interconnect materials in SOFC fuel cells. A La0.67Sr0.33MnO3La0.67Sr0.33MnO3 (LSM) thin film is coated on these materials using pulsed DC magnetron sputtering. The as-deposited film is amorphous but is transformed into perovskite structure after annealing at different temperatures and times. The coating and uncoated structures and surface morphologies are analyzed using X-ray diffraction (XRD), electron Probe Micro Analyzer (EPMA), X-ray photoelectron spectroscopy (XPS), and scanning electron microscopy (SEM). The result shows that the LSM thin film on Crofer22 APU is good for compaction and adhesion, but there are some stresses between the equivalent ZMG232 and the coating and then create some cracks on the coating. Thereby, the coefficients of thermal expansion (CTE) of the equivalent ZMG232 may be higher than the CTE of the LSM. The cross-section of equivalent ZMG232 did not allow diffusion of Cr element. Thus, coating by plasma-sputtering could prevent the growth of oxide and the diffusion of Cr element to avoid cathode poisoning and the decline of conductivity in SOFC at high temperature.