| 摘要 |
PURPOSE:To suppress the lowering in the detection capacity of an oxygen concn. sensor, by providing a first layer comprising an metal oxide semiconductor containing platinum on an insulating substrate and further providing a second layer comprising a metal oxide semiconductor with reduced platinum content thereon. CONSTITUTION:A first layer 21 comprising a metal oxide semiconductor such as titania containing platinum on an insulating substrate 20 and a second layer 22 comprising a metal oxide semiconductor such as titania with platinum content lower than that of the first layer 21 is applied to said first layer 21. The first and second layers are baked so as to form a porous structure and electric heating wires 24 and electrodes 23 are provided in an embedded state. The concn. of oxygen is detected from the resistance value corresponding to oxygen partial pressure. At this time, even if atmospheric gas is raised to high temp. and platinum in the first layer is grown into a large particle size to be escaped, said platinum is caught by the second layer 22. Because the detection capacity of the concn. of oxygen of the second layer 22 is enhanced even if the detection capacity of the concn. of oxygen of the first layer is lowered, the lowering in the detection capacity of the concn. of oxygen can be suppressed as a whole. |
