Influence of sensing electrode and electrolyte on performance of potentiometric mixed-potential gas sensors

The influence of the chemical composition and microstructure such as morphology of the tin-doped indium oxide (ITO) sensing electrode and the types of the solid-state oxygen conducting electrolytes such as yttria or scandia-stabilized zirconia (YSZ or ScSZ) and perovskite-type La0.85Sr0.15Ga0.8Mg0.2O(3−0.35/2) (LSGM) on the sensing properties of the mixed-potential gas sensors has been investigated. It was found that the sensitivity of the sensor with ScSZ and ITO as the electrolyte and sensing electrode, respectively, decreased although the magnitude of the sensor signal was found to increase as the concentration of tin in the ITO composite increased. The sensor using the spherical ITO particles as the sensing electrode exhibited higher sensitivity than that of the sensor employing the ITO powders with coexisting rod-like and spherical morphologies. The sensitivity of the sensor based on YSZ electrolyte did not show much difference from that of the ScSZ-based sensor. However, the sensor utilizing the perovskite-type oxygen ion conductor (LSGM) displayed much lower sensitivity and much slower response to the test gas than those based on stabilized zirconia.