Investigation of a reference electrode based on perovskite oxide for second kind potentiometric gas sensor in open systems

Different oxygen electrodes are compared to be used in second kind gas sensors. Perovskite oxides (La1−xSrxMnO3), RuO2, platinum and gold deposited on NASICON electrolyte were characterized by impedance spectroscopy in different atmospheres (argon, synthetic pure air or with 5% CO2). They were also mixed with Na2Ti6O13–TiO2 and Na2Ti3O7–Na2Ti6O13 to improve the reversible exchange of oxygen and sodium at the interfaces. Results show that the resistance of the platinum electrode is generally smaller than the perovskite one hundred or thousand times smaller than the gold one when they are deposited alone. The best results when using mixtures are obtained for the Na2Ti3O7–Na2Ti6O13 system mixed with La0.8Sr0.2MnO3 for which a sensitivity to oxygen is observed.