Plasma-Sprayed (Bi₂O₃)_0.705 (Er₂O₃)_0.245 (WO₃)_0.05 Electrolyte for Intermediate-Temperature Solid Oxide Fuel Cells (IT-SOFCs)

Stabilized bismuth oxide material with fluorite structure (δ-Bi₂O₃) has been studied as a promising electrolyte material for intermediate temperature solid oxide fuel cells (IT-SOFCs) due to its high oxygen ion conductivity in mediate temperature. Especially, the ternary system Bi₂O₃-Er₂O₃-WO₃ is widely concerned for its high ionic conductivity and thermal stability. In this study, regarding its low melting point, the possibility to deposit dense Bi₂O₃-Er₂O₃-WO₃ ((Bi₂O₃)_0.705 (Er₂O₃)_0.245 (WO₃)_0.05, EWSB) electrolyte by plasma spraying was examined. It was confirmed that the sintered EWSB bulk presents a high ion conductivity of 0.34 S cm⁻¹ at 750 °C and excellent stability that indicates no structure transformation and conductivity degradation after annealing at 600 °C for 1000 h. The phase structure and cross-sectional microstructure of plasma-sprayed EWSB were characterized by XRD and SEM. Results showed that the as-plasma-sprayed EWSB presents a dense microstructure with well bonded lamellae. The XRD showed the formation of EWSB with δ-phase and a trace of β-phase, while the β-phase disappeared after annealing at 750 °C for 10 h. The deposited EWSB electrolyte presented the excellent ionic conductivity of 0.26 S cm⁻¹ at 750 °C which can be directly applied to SOFC at intermediate temperature.