Performance of Plasma-sprayed Bi2O3–Er2O3–WO3 for Intermediate-Temperature Solid Oxide Fuel Cells (IT-SOFCs)

Stabilized bismuth oxides with fluorite structure (δ-Bi₂O₃) such as Bi₂O₃–Er₂O₃–WO₃ are promising electrolyte material for intermediate temperature solid oxide fuel cells due to its high oxygen ion conductivity in mediate temperature. In this study, considering its low melting point, the possibility to deposit dense electrolyte by plasma spraying was examined by plasma spraying of Bi₂O₃)_0.705 (Er₂O₃)_0.245 (WO₃)_0.05 (EWSB). The phase structure and cross-sectional microstructure of plasma-sprayed EWSB were characterized by XRD and SEM. It was confirmed that the EWSB bulk presents high ion conductivity of 0.23 S cm^-1 at 700 °C and excellent stability without structure change and conductivity degradation after annealing at 600 °C for 1000 h. The as- sprayed EWSB presents a dense microstructure with well bonded lamellae. The XRD revealed the diffraction peaks of δ-phase and trace of β-phase which disappeared after annealing at 750°C for 10h. The deposited EWSB presented the conductivity of 0.15 S cm^-1 at 700 °C and reached 65% of the sintered bulk at the correspondent temperature. The SOFC cell was also assembled with Ni-based anode and La_xSr_1-xCoO₃ cathode to examine the performance of the plasma-sprayed electrolyte. The relationships between EWSB deposit microstructure, ionic conductivity, and cell output performance are examined.