Enhanced long-term stability of bismuth oxide-based electrolytes for operation at 500 °C
Cubic-stabilized ((DyO1.5)x–(WO3)y–(BiO1.5)1 − x − y) electrolytes (DWSB) with much higher conductivity than (ErO1.5)0.2(BiO1.5)0.8, 20ESB, were developed through a double-doping strategy. (DyO1.5)0.08–(WO3)0.04–(BiO1.5)0.88, 8D4WSB, is the highest conductivity composition but underwent the greatest conductivity degradation at 500 °C due to its low total dopant concentration. The effect of dopant composition on conductivity behavior with time at 500 °C demonstrates that there is a trade-off between initial conductivity and long-term stability at this temperature. Therefore, it is necessary to find an optimal total and relative concentration of dopants to provide the enhanced long-term stability needed to make this DWSB electrolyte system feasible for 500 °C operation. To this end, it was found that (DyO1.5)0.25–(WO3)0.05–(BiO1.5)0.70, 25D5WSB, maintained a conductivity of 0.0068 S/cm without appreciable degradation after annealing at 500 °C for 500 h. Moreover, since bismuth oxide-based electrolytes do not exhibit any grain boundary impedance, the total conductivity of 25D5WSB is significantly higher than that of alternate electrolytes (e.g., GDC: Gd0.1Ce0.9O1.95) at this temperature.
KeywordsBismuth oxide Electrolyte Conductivity Stability Electrochemical impedance spectroscopy
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