Plasma-sprayed bulk-like yttria-stabilized zirconia coatings for solid oxide fuel cell electrolytes based on liquid-phase sintering-induced interfacial healing

To achieve a coating density meeting the solid oxide fuel cell (SOFC) electrolyte requirements of high gas tightness and ionic conductivity, in this study, a new interface healing densification process based on a liquid-phase sintering induction mechanism was conducted on plasma-sprayed 8 mol% Y₂O₃-stabilized ZrO₂ (8YSZ) coatings. Using Fe₂O₃ and Bi₂O₃ as healing additives, metallurgical healing of unbound interfaces was achieved by impregnating the additives into the gap interfaces, followed by liquid-phase sintering at 1200 and 1050 °C. After healing, the YSZ coating exhibited a dense bulk-like microstructure with a significant reduction in the gas leakage rate by two orders of magnitude, and the oxygen ion conductivity of the coating was significantly increased. The YSZ coating healed with the Fe₂O₃ additive showed an oxygen ionic conductivity nearly one order of magnitude higher than that of the as-sprayed coating, reaching more than 80% of the value of the high-temperature-sintered YSZ bulk.