MANGANESE-DOPED BISMUTH VANADATE SOLID ELECTROLYTES - OXYGEN PERMEATION IN BI2V0.8MN0.2O5.3

Oxygen permeation and transference number measurements have been made on dense membranes of Bi2V0.8Mn0.2O5.3. Measurements of the permeation flux as a function of membrane thickness and oxygen partial pressure gradient suggest that the oxygen transport is limited by bulk diffusio n rather than by surface exchange kinetics. The electronic conductivit y of the sample at 750-850 degrees C was obtained from the permeation flux measurements and found to be in the range 2 x 10(-3)-10(-2) S cm( -1). The transference numbers were measured by a potentiometric techni que in two oxygen partial pressure gradients. The values range from 0. 67 at 550 degrees C to 0.82 at 850 degrees C. At high temperature, the transference numbers measured by the potentiometric technique are in close agreement with those derived from the permeation flux and the to tal electrical conductivity data. At lower temperatures, the results a re significantly different, most likely due to slow electrode kinetics .