| 摘要 |
PURPOSE:To suppress the decrease of the resistance of a sensor with lapse of time and to prevent the breakdown thereof by impregnating a silicic acid soln. having a prescribed degree of polymn. to a molding formed by embedding electrodes therein and precalcining the molding, then subjecting the molding to normal calcination under specific conditions. CONSTITUTION:The molding 6 of SnO2 embedded therein with electrode 2 in common use as a heater and the detecting electrode 4 is precalcined and thereafter, the soln. of silica having 2-3 average degree of polymn. is dropped onto the molding 6 to impregnate the silica therein. The electrodes 2, 4 are energized after air drying, by which the molding is subjected to the normal calcination for 10-60min at 700-800 deg.C. The silica added to the molding 6 is penetrated into the molding by the normal calcination and is deposited on the surface of the molding 6 to form a silica film 8. The resistance change of the sensor with lapse, of time is decreased and the breakdown thereof is hardly generated according to the above-mentioned method.
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