PURPOSE: To improve the gas selectivity without spoiling basic charateristics of a gas sensor, by forming a layer of oxide ultrafine particles by mixing most portions of the oxide ultrafine particle having semiconductor characteristics and of a catalyst metal under the state of face-face contact.
CONSTITUTION: An insulating substrate 3 is made of aluminum oxide and an electrode 4 and an ultrafine particle film 3 are formed on the substrate 3. Said substrate 3 is immersed in an aqueous solution of platinic acid chloride whose concentration of catalyst metal is about 100g/l and hereafter, it is dried in hydrogen at 90°C for 30min. Hereby, about 1.5wt% catalyst metal is mixed with the oxide ultrafine particles in face-face contact with each other in the oxide ultrafine particle film. The quantity of the catalyst metal interposing between the oxide ultrafine particles is adjusted to the most effective quantity by adjusting the concentration of the catalyst metal.
MITSUYOSHI TADAHIKO
TAGUCHI MITSUO
