Effect of Sr addition to La-based perovskite-type oxide as an electrode material for zirconia-based amperometric-type NOx sensor

The sensing characteristics of an amperometric NOx sensor with yttria-stabilized zirconia and a La-based perovskite-type oxide sensing electrode were examined. La_1-xSr_xMO₃ (M = Co, Mn, x = 0, 0.2, 0.4, 0.6) were synthesized using the spray pyrolysis method. The NO₂ response of a sensor fabricated with La_1-xSr_xMnO₃ increased with increasing amount of Sr, and the trend was in contrast to that of the sensors fabricated with La_1-xSr_xCoO₃. LaSr_0.2MnO₃ was determined to be the most appropriate material for the sensor in terms of a high NO₂ response and low O₂ current. In order to discuss the effects of Sr addition to La-based perovskite oxides for the sensor, NO adsorption and desorption properties of oxides and the relationship between the oxidation number of the B-site cation and Sr substitution were examined using temperature-programmed desorption and X-ray photoelectron spectroscopy, respectively.