Thermoelectric gas sensors of different catalyst oxides and heater metals

Thermoelectric hydrogen sensors with different catalyst oxides, Pt-Al ₂O₃ and Pt-CeO₂ have been prepared, and their gas sensing properties are investigated in the air and N₂ flow. In air, the relationship between the sensor output and the gas concentration is a linear indicating the combustion only depends on the gas concentration in air. In N₂ atmosphere, where the oxygen gas content of N₂ source cylinder is below the industrial standard of 50 ppm, the sensor output shows also a linear relationship with the gas concentration, but depressed signal level. The microheater of the thermoelectric sensor has been prepared by the co-sputtering of tungsten and platinum to enhance the high temperature stability. The temperature coefficients of the Pt-W alloy multilayer heater were lowered to a half of the level of Pt.