Electrodes for oxygen sensors based on rate earth manganites or cabaltites

Abstract Rare earth manganites and cobaltites are particularly suitable electrode materials for solid electrolyte oxygen sensors. Perovskite-type manganites Ln1−xCa(Sr)xMnO3 (Ln=La, Nd, Gd, Yb, Y; x = 0−0.5) and cobalties Ln1−xSrxCoO3 (Ln  La, Pr, Nd, Sm; x = 0–1), SrCo1−xFexO3 (x = 0–0.5) were prepared in air by sintering at T = 1270–1570 K. The formation of the perovskite-type phase was confirmed by X-ray powder diffraction results. The cation concentrations were determined by atom absorption spectroscopy. Isothermal oxygen permeation measurements were performed with zirconia solid electrolyte tubes by using a special glass for sealing and adjusting the oxygen solid electrolyte pump. From ultraviolet photoemission spectroscopy (UPS) we determined the work function Φ of electrons, the position of the Fermi level in relation to the valence band edge (EF – EV), and the change of the ionization potential (ΔI) as a function of temperature. The polarization resistivity of perovskite-type oxide electrodes on Bi0.75Y0.25O1.5 solid electrolytes was determined from the steady-state current density overpotential curves which were measured in a three-electrode arrangement.

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