Plasma-Sprayed La0.2Sr0.8MnO3-La0.3Sr0.7TiO3 Bilayer Coatings Along with the Interface Healing Processing Applied as the High Dense Interconnector for Tubular Solid Oxide Fuel Cells

Plasma spraying, an important coating and film preparation technology, provides a crucial method for depositing ceramic-based interconnects on tubular solid oxide fuel cells. However, traditional plasma-sprayed ceramic coatings exhibit typical lamellar porous structures with numerous unbound interfaces and gas-permeable channels, which makes it difficult to meet the microstructural requirements to prevent the leakage of fuel gas and oxidizing gas. This leads to the lower conductivity of the coating compared to the sintered bulk, and results in increased ohmic resistance and reduced output performance. To improve the interface bonding and conductivity of plasma-sprayed La_0.2Sr_0.8MnO₃-La_0.3Sr_0.7TiO₃ (LSM-LST) bilayer interconnects for tubular cells, a Co₃O₄ healing additive was added to the gap interfaces within the LST and LSM coatings. Results showed that metallurgical healing occurred at unbound interfaces and microcracks due to the liquid-phase sintering mechanism, and a bulk-like dense microstructure was obtained at a lower temperature (1200 °C) compared to the dense sintering temperature of the bulk. Moreover, the gas leakage rates of the stable coatings after interface healing were > 1 order of magnitude lower than that of the as-sprayed coatings. Additionally, their electrical conductivity was more than twice that of the as-sprayed coatings, which meets the microstructural and performance requirements of tubular cell interconnects.