Low temperature operation of thin-film limiting-current type oxygen sensor using graded-composition layer electrodes

A thin-film limiting-current type oxygen sensor incorporating graded-composition layers (GCL) was fabricated. The layers were formed by changing the sputtering power so that the mixing ratio of Pt and yttria-stabilized zirconia (YSZ) may changed continuously. The electrode interface resistance of the sensor has greatly decreased by inserting GCL between Pt electrode and YSZ electrolyte. In addition, the temperature dependence of the electrode interface resistance in the sensor with GCL has also become small. Therefore, even if the heat temperature of the sensor with GCL was decreased by 100–150 °C more than that of the sensor without GCL, the sensor with GCL could maintain the sensor output. It was demonstrated that the insertion of GCL was highly effective in decreasing the operating temperature of the thin-film limiting-current type sensor. Shortening of the warm-up time can be expected by using this electrode.