PURPOSE: To bring a ceramic tube into proper contact with a platinum electrode, stabilize the output and improve the durability of an oxygen sensor by burying platinum particles inside a ceramic substrate which is formed on the outer surface and near the electrode while bringing the particles into touch with the electrode.
CONSTITUTION: Electrodes 2, 3 respectively made of platinum for taking out motive electric power are respectively installed in a part of each inner surface and outer surface 11 of a ceramic tube 1 as a ceramic substrate which has a closed top part and consists of mainly zirconium oxide. A platinum catalyst layer 4 is formed further on the outer surface 11 of the ceramic tube 1 by evaporation of platinum and it is protected with a protective layer 5 of a metal oxide such as magnesium spinel. In the inside 13 of the ceramic tube 1 near the electrode 3, platinum particles 21 are buried while being brought into contact with the electrode 3. The particle size of the platinum particles 21 is made larger as the particles are nearer the surface of the ceramic tube 1. Consequently, the contact of the platinum electrode with the ceramic substrate is improved and thus stable output is obtained.
UCHIKAWA AKIRA
KAWASHIMA MASAMI
NEMOTO KOICHI
KANEKO HIROAKI
NISSAN MOTOR