Cubic-stabilized ((DyO1.5)(x)-(WO3)(y)-(BiO1.5)(1-x-y)) electrolytes (DWSB) having higher conductivity than (ErO1.5)(0.2) (BiO1.5)(0.8) (20ESB) were developed. However, this DWSB composition also experienced a conductivity degradation like other cubic stabilized bismuth oxides in intermediate temperature (IT) ranges, i.e. 500 degrees-700 degrees C. Several DWSB compositions with the same 2:1 dopant content ratio (Dy:W) were annealed to determine the conductivity behavior in the IT range with time. All DWSB compositions maintained their initial conductivity at 700 degrees C, but underwent conductivity degradation at < 600 degrees C. The effect of total dopant concentration on the conductivity degradation behavior was investigated at 600 degrees and 500 degrees C. It was also found that 8D4WSB, which is the highest conductivity composition, has promise as an electrolyte for an isothermal operation above 650 degrees C or below 400 degrees C.