JPH06347439A - Regulating method for area of electrode for oxygen sensor - Google Patents

Abstract

PURPOSE:To form a uniform electrode of which effective area as a catalyst is regulated even on a substance having a complicate shape by forming a dense glass film having no oxygen ion permeability on the area not to act as the catalyst. CONSTITUTION:An electrode having uniform thickness is formed by electroless plating, etc., on an oxygen ion conductive solid electrolyte. A dense glass film having no oxygen ion permeability is formed on the area not to act as a catalyst. In the glass film used, a good result is exerted by a glass film formed by applying and burning paste obtained by kneading a mixture comprising 34.7-64.4wt.% of CaO-PbO-B2O3-SiO2-based amorphous glass, 6.3-11.7wt.% of SrO-ZnO-TiO2-Al2O3-B2O3-SiO2-based crystalline glass, 14.4-26.7wt.% of Al2O3 powder, and 14.7-27.3wt.% of CaZrO3 powder with a vehicle contg. 4.4-8.2wt.% of ethyl cellulose with a ratio (in wt. ratio) of 100:24.6-100:50.1.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an oxygen sensor, and more particularly to an oxygen sensor for measuring the oxygen concentration in exhaust gas of an internal combustion engine such as an automobile and controlling the air-fuel ratio of these internal combustion engines. This is a method of regulating the area acting as a catalyst to a constant value.

[0002]

2. Description of the Related Art A paste containing a platinum group metal as an ion or metal is formed on an oxygen ion conductive solid electrolyte.
An electrode is formed on the oxygen ion conductive solid electrolyte by applying it so as to have a certain area by a general method such as screen printing and then decomposing this paste by thermal decomposition or the like. There is also a method in which an electrode is formed on the entire surface of the oxygen ion conductive solid electrolyte by performing electroless plating, and the electrode other than the portion that should function as a catalyst is polished and removed.

[0003]

When an oxygen ion conductive solid electrolyte having a complicated shape is used, an electrode having a uniform thickness is formed over a certain area by the method using the above paste. Is difficult to do, while
According to the electroless plating method, it is difficult to polish and remove the formed electrode. The present invention solves the above-mentioned problems and provides a method for forming a stable electrode having a restricted effective area as a catalyst even on an object having a complicated shape.

[0004]

Means for Solving the Problems An electrode having a uniform thickness is formed on an oxygen ion conductive solid electrolyte by electroless plating or the like, and a dense glass having no oxygen ion permeability in a portion which should not act as a catalyst. Form a film. The glass film used here is a CaO-PbO-B ₂ O ₃ -SiO ₂ -based amorphous glass 3
4.7 to 64.4 _{wt%, SrO-ZnO-TiO 2} -Al 2 O 3 -B 2 O 3 -SiO 2 based crystalline glass 6.3 to 11.7 wt%, Al ₂ O ₃ powder 14.4 to 26.7 wt%, CaZrO ₃ powder 14.7 ~ 27.3% by weight of the mixture,
A glass film formed by coating and firing a paste made by kneading a vehicle containing 4.4 to 8.2% by weight of ethyl cellulose in a ratio of 100: 24.6 to 100: 50.1 (weight ratio) gives particularly good results. Show.

[0005]

[Function] The catalytic reaction occurring at the electrode of the oxygen sensor occurs only at the three-phase coexistence point of the electrode, the oxygen ion conductive solid electrolyte and the measurement gas. When a dense glass film having no oxygen ion permeability is formed on the electrode, the electrode, the oxygen ion conductive solid electrolyte and the measurement gas do not coexist in that portion. Therefore, no catalytic reaction occurs.

[0006]

Example 1 Oxygen ion conductive solid electrolyte 8 mol
Pt is deposited on the Y ₂ O ₃ modified ZrO ₂ Tamman tube by electroless plating.
The (electrode) was deposited. A polyimide tape was attached to a portion of the electrode that should have catalytic activity, and then the entire surface of the Tammann tube was covered with CaO-PbO-B ₂ O ₃ -SiO ₂ -based amorphous glass 49.5% by weight, SrO-ZnO-TiO ₂ -Al. ₂ O ₃ -B ₂ O ₃ -SiO ₂ system crystalline glass 9.0
% By weight, Al ₂ O ₃ powder 20.5% by weight, CaZrO ₃ powder 21.0% by weight
And a vehicle containing 6.3% by weight of ethylcellulose were kneaded in a ratio of 100: 39 (weight ratio) to apply a paste. After drying the paste,
The polyimide tape was peeled off. Finally, the paste was pyrolyzed by heating at 1100 ° C for 10 minutes in an electric furnace. The Pt electrode was exposed only on the portion where the polyimide tape was attached, and the other portion was covered with dense glass.

[0007]

Example 2 Oxygen ion conductive solid electrolyte 8 mol
Pt is deposited on the Y ₂ O ₃ modified ZrO ₂ Tamman tube by electroless plating.
The (electrode) was deposited. A polyimide tape was attached to a portion of the electrode that should have catalytic activity, and then the entire surface of the Tammann tube was filled with CaO-PbO-B ₂ O ₃ -SiO ₂ -based amorphous glass 39.6% by weight, SrO-ZnO-TiO ₂ -Al. ₂ O ₃ -B ₂ O ₃ -SiO ₂ system crystalline glass 11.7
% By weight, Al ₂ O ₃ powder 21.4% by weight, CaZrO ₃ powder 27.3% by weight
And a vehicle containing 6.3% by weight of ethylcellulose were kneaded in a ratio of 100: 24.6 (weight ratio) to apply a paste. After the paste was dried, the polyimide tape was peeled off. Finally in the electric furnace 1100
The paste was pyrolyzed by heating at 0 ° C for 10 minutes. The Pt electrode was exposed only on the portion where the polyimide tape was attached, and the other portion was covered with dense glass.

[0008]

Example 3 Oxygen ion conductive solid electrolyte 8 mol
Pt is deposited on the Y ₂ O ₃ modified ZrO ₂ Tamman tube by electroless plating.
The (electrode) was deposited. A polyimide tape was attached to a portion of the electrode that should have catalytic activity, and then the entire surface of the Tammann tube was filled with CaO-PbO-B ₂ O ₃ -SiO ₂ -based amorphous glass 64.4 wt%, SrO-ZnO-TiO ₂ -Al. ₂ O ₃ -B ₂ O ₃ -SiO ₂ system crystalline glass 6.3
% By weight, Al ₂ O ₃ powder 14.6% by weight, CaZrO ₃ powder 14.7% by weight
And a vehicle containing 6.3% by weight of ethyl cellulose were kneaded at a ratio of 100: 50.1 (weight ratio) to apply a paste. After the paste was dried, the polyimide tape was peeled off. Finally in the electric furnace 1100
The paste was pyrolyzed by heating at 0 ° C for 10 minutes. The Pt electrode was exposed only on the portion where the polyimide tape was attached, and the other portion was covered with dense glass.

[0009]

Comparative Example 1 Oxygen ion conductive solid electrolyte 8 mol
Pt is deposited on the Y ₂ O ₃ modified ZrO ₂ Tamman tube by electroless plating.
The (electrode) was deposited. A polyimide tape was attached to a portion of the electrode that should have catalytic activity, and then the entire surface of the Tammann tube was coated with CaO-PbO-B ₂ O ₃ -SiO ₂ -based amorphous glass 30.0 wt% and SrO-ZnO-TiO ₂ -Al. ₂ O ₃ -B ₂ O ₃ -SiO ₂ system crystalline glass 21.3
% By weight, Al ₂ O ₃ powder 21.4% by weight, CaZrO ₃ powder 27.3% by weight
And a vehicle containing 6.3% by weight of ethylcellulose were kneaded in a ratio of 100: 24.6 (weight ratio) to apply a paste. After the paste was dried, the polyimide tape was peeled off. Finally in the electric furnace 1100
The paste was pyrolyzed by heating at 0 ° C for 10 minutes. Many holes of several μmφ were generated in the formed glass film.

[0010]

Comparative Example 2 Oxygen ion conductive solid electrolyte 8 mol
Pt is deposited on the Y ₂ O ₃ modified ZrO ₂ Tamman tube by electroless plating.
The (electrode) was deposited. A polyimide tape was attached to a portion of the electrode that should have catalytic activity, and then the entire surface of the Tammann tube was filled with CaO-PbO-B ₂ O ₃ -SiO ₂ -based amorphous glass 65.0% by weight, SrO-ZnO-TiO ₂ -Al. ₂ O ₃ -B ₂ O ₃ -SiO ₂ system crystalline glass 5.9
% By weight, Al ₂ O ₃ powder 14.4% by weight, CaZrO ₃ powder 14.7% by weight
And a vehicle containing 6.3% by weight of ethyl cellulose were kneaded at a ratio of 100: 50.1 (weight ratio) to apply a paste. After the paste was dried, the polyimide tape was peeled off. Finally in the electric furnace 1100
The paste was pyrolyzed by heating at 0 ° C for 10 minutes. Many holes of 100 μmφ were generated in the formed glass.

[0011]

According to the present invention, a dense glass film having no oxygen ion permeability can be formed in a portion of an electrode formed on an oxygen ion conductive solid electrolyte, which should not act as a catalyst. This makes it possible to regulate the area of the electrode formed on the oxygen ion conductive solid electrolyte, which is effective as a catalyst.

Claims (2)

[Claims] 1. A method for controlling the area of an electrode formed on an oxygen ion-conducting solid electrolyte that is effective as a catalyst, wherein a dense glass having no oxygen ion permeability is present in a portion of the electrode which should not have catalytic activity. A method for regulating the area of an electrode for an oxygen sensor, which comprises forming a film. 2. The glass film comprises CaO—PbO—B ₂ O ₃ —SiO ₂ -based amorphous glass 34.7 to 64.4% by weight, SrO—ZnO—TiO ₂ —Al ₂ O ₃ —B ₂ O.
₃ -SiO ₂ type crystalline glass 6.3 to 11.7% by weight, Al ₂ O ₃ powder 14.
A mixture of 4 to 26.7% by weight and 14.7 to 27.3% by weight of CaZrO ₃ powder and a vehicle containing 4.4 to 8.2% by weight of ethyl cellulose are kneaded at a ratio of 100: 24.6 to 100: 50.1 (weight ratio). The method for controlling the area of an electrode for an oxygen sensor according to claim 1, wherein the glass film is a dense glass film having no oxygen ion permeability formed by applying and firing a paste.