Preparation of BiMeVOx (Me = Cu, Ti, Zr, Nb, Ta) compounds as solid electrolyte and behavior of their oxygen concentration cells

A group of complex metal oxides, BiMeVOx, which a fraction (x) of V in Bi4V2O11 is replaced by foreign metal, has been reported to be oxide-ionic conductors. The various kinds of oxides in this group, Me = Cu (x = 0.1), Zr (x = 0.1), Ti (x = 0.4), Nb (x = 0.15) and Ta (x = 0.15), were investigated for electrochemical characterization based on oxygen concentration battery. The powders of BiMeVOx, their structural phases to the high temperature phase (γ) of Bi4V2O11, were obtained by calcining at 700-850 °C. Each sample was compacted into a disk, and installed into an oxygen concentration cell. The oxygen concentration cells using the resulting disks of BiMeVOx, especially Me = Cu, were found to work as an oxygen sensor fairly well at 700 °C: the number of reaction electrons (n) associated with the reduction of O2 was close to the theoretical one (4). With lowering operating temperature, however, the O2-responding properties degraded rather quickly: it was far larger at 500 °C. Such degradation was confirmed to be owing to decrease the rate of electrode reactions through the measurement of Faraday efficiency of oxygen pumping current. As a result, the performances of the cells were found to depend very much on the kinds of electrode materials. The use of a perovskite-type oxide, La0.6Sr0.4Co0.8Fe0.2O3, instead of Pt as a electrode was found to enable the cell to work at 400 °C and above.