Structural characterization of La0.67Sr0.33MnO3 protective coatings for solid oxide fuel cell interconnect deposited by pulsed magnetron sputtering

Films made of La0.67Sr0.33MnO3 (LSM) were deposited by pulsed direct current (DC) magnetron sputtering at ambient temperature. After annealing in air at temperature from 600 to 900 deg. C, the crystallographic structure and phase composition were studied using X-ray diffraction and scanning electron microscopy. Area specific resistance (ASR) of the coated specimen was measured with the standard DC four-point approach at 750 deg. C in air. Adding oxygen during deposition increased crystallization temperature from an amorphous to a perovskite phase and decreased the deposition rate. After annealing, excess oxygen in the films produced additional oxide segregations at the specimen surface and left bubble holes after spallation. The specimen ASR after 1050 h at 760 deg. C was 39.5 mΩ. The degradation rate was 3.5 mΩ per 1000 h, considerably lower than the standard for auxiliary power unit application. Preliminary results in this study show that LSM films deposited by pulsed DC magnetron sputtering are good candidates for protective coating of solid oxide fuel cell interconnects