| 摘要 |
PURPOSE:To obtain an oxygen sensor having good durability by forming a lead trap layer of a porous ceramic material so as to have >=0.3cc/g and <=5cc/g pore volume and >=200mu and <=1,000mu thickness. CONSTITUTION:Platinum electrodes 12, 13 are respectively provided on the inside and outside surface of a ceramic pipe 11 essentially consisting of zirconium oxide having closed ends and platinum is deposited by evaporation on the electrode 13 on the outside surface side to form a catalyst layer 14. A metallic oxide such as magnesium spinel is further thermally sprayed thereon to form a protective layer 15 and the lead trap layer 16 having >=0.3cc/g and <=5cc/g pore volume and >=200mu and <=1,000mu thickness is formed on the layer 15 by using the porous ceramic material such as gamma-alumina having a large specific area. Since the thickness of the layer 16 is large, the trapping amt. of the lead component is increased. The lead component contained in an exhaust gas is adsorbed by the gamma-alumina of the layer 16. On the other hand, the exhaust gas is made to arrive quickly at the layer 14 as the pore volume is large. The decrease of the reaction rate is thereby obviated. The durability of the oxygen sensor is thus improved. |
