PEROVSKITE ELECTRODES FOR SENSORS

The data published on perovskite oxides La1-xSrxBO3-delta (B = Co, Cr, Fe, Mn) are compared to assess their use as electrodes in applications such as fuel cells, low temperature oxygen meters, etc. The oxides are reviewed in terms of their stability in temperature and oxygen partial pressure of operation, nonstoichiometry, conductivity and catalytic properties and the effect of the strontium substitution content, x. From this comparison it is found that La1-xSrxCrO3-delta is better suited for applications in reducing conditions, while La1-xSrxCoO3-delta is better suited for applications at higher oxygen potentials. While noble metals like platinum are currently being used for these applications, the perovskite oxides offer better kinetics at lower temperatures. To compare the kinetics, the electrochemical cell: air, electrode/ Bi-based or Zr-based electrolyte/ electrode, air was used and the overpotential of the interfaces was measured. The electrodes used for this comparison are Pt, La0.7Sr0.3MnO3-delta, and La0.7Sr0.3CoO3-delta. The results show that for temperatures lower than 800-degrees-C, the oxide electrodes performed better than platinum. This is attributed to the ease of transfer of oxygen potential between the electrodes and the electrolyte.