Effect of sensor thickness on trimethylamine sensitivity of In2O3-MgO sensors loaded with noble metals

Variations in trimethylamine (TMA) sensitivity with sensor thickness as well as operating temperature have been investigated with thick film In2O3-MgO (5 mol%)-based sensors with interior electrodes. The sensitivity of pure In2O3-MgO (5 mol%) tended to exhibit a maximum TMA sensitivity at a certain sensor thickness at temperatures lower than 530 degrees C. Loading of 0.5 wt% Pt led to a monotonous decrease in sensitivity with increasing thickness even at a temperature as low as 300 degrees C, and then to a significant decrease in sensitivity. In contrast, the sensitivity enhancement induced by the loading of 0.5 wt% Au remained almost unchanged up to about 2.5 mm thick, especially at temperatures lower than 375 degrees C. Among the sensors tested, the Au-loaded sensor with around 2 mm thick exhibited the highest TMA sensitivity at 300 degrees C.