Enhanced long-term stability of bismuth oxide-based electrolytes for operation at 500 A°C

Cubic-stabilized ((DyO1.5) (x) -(WO3) (y) -(BiO1.5)(1 -aEuro parts per thousand x -aEuro parts per thousand 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 A degrees C due to its low total dopant concentration. The effect of dopant composition on conductivity behavior with time at 500 A degrees 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 A degrees 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 A degrees 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.