Plasma-Sprayed High-Performance (Bi₂O₃)_0.75(Y₂O₃)_0.25 Electrolyte for Intermediate-Temperature Solid Oxide Fuel Cells (IT-SOFCs)

Rare earth element-doped bismuth oxides with the fluorite structure (δ-Bi₂O₃) exhibit high oxygen ion conductivity at low temperature, which is promising electrolyte materials for intermediate-temperature solid oxide fuel cells (IT-SOFCs). However, traditional co-sintering process is not applicable to the manufacturing of IT-SOFCs using low melting point Bi₂O₃-based electrolyte, while further high-temperature processing is not required for deposition Bi₂O₃-based electrolytes. In this study, plasma spraying was used to examine the possibility to deposit high-performance Bi₂O₃-based electrolytes without the following high-temperature process. (Bi₂O₃)_0.75 (Y₂O₃)_0.25 (YSB) spray powders were prepared by the sinter-crushing method. The YSB electrolytes were fabricated by plasma spraying at different deposition temperatures. The effects of deposition temperature on the coating microstructure, crystalline stability, and ion conductivity were investigated. Results showed that the as-sprayed YSB electrolytes present a dense microstructure with well-bonded lamellar interfaces. The pure δ-phase YSB electrolyte was deposited with 37.5-75 μm powders at a deposition temperature of 350 °C. The deposited YSB electrolyte presented the excellent ionic conductivity of 0.19 S cm⁻¹ at 700 °C in comparison with 0.21 S cm⁻¹ for sintered bulk.