JPH055713A - Method for manufacturing gas detection element - Google Patents

Abstract

(57) [Summary] [Purpose] A low temperature sintering is performed without using a silica or alumina type binder to obtain a gas detection element having neither mechanical strength nor humidity dependency. [Structure] After mixing tin oxide ultrafine particles 4 having an average particle size of 50Å with fine particles of tin oxide 4 having a particle size of 200Å or more, kneading with water to form a paste, which is applied onto the insulating substrate 1 and dried,
After that, the tin oxide fine particles 4 are solidified by sintering at 800 ° C. or lower to obtain a mechanically strong gas detection element using the tin oxide ultrafine particles 5 as a binder.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION The present invention is to improve the mechanical strength by firmly sintering tin oxide fine particles by using a binder containing tin oxide ultrafine particles as a main component and to improve the humidity dependency of gas sensitivity. The present invention relates to a method for manufacturing a suppressed gas detection element.

[0002]

_2. Description of the Related Art Conventionally, in the manufacture of a gas sensing element of a metal oxide sintered body such as SnO ₂ or ZnO, a strong sintering temperature of 1000 ° C. or higher is maintained in order to maintain the gas sensitive activity. 800 because it cannot be sintered at high temperature
Low temperature sintering below ° C had to be performed. For this reason, the sintering strength is remarkably weaker than that of ordinary ceramics, and the mechanical strength sufficient to withstand shock and vibration during general use cannot be obtained. Therefore, various proposals have been made to increase the mechanical strength of the gas detection element. On the other hand, currently commercially available gas detection elements use silica made of an organosilicon compound as a binder, and silica sol and the like are also used in other research and development stages. Alumina sol, silica sol, etc. are also used in the research and development stage.

[0003]

However, the conventional ones sintered with these binders have SiO ₂ and A.
Since l ₂ O ₃ remains and the silica and alumina are very hygroscopic, the gas sensitivity of the gas detection element is highly dependent on humidity, and also changes over time in a high humidity atmosphere. was there.

The present invention has been made in order to solve the above-mentioned drawbacks, and it is possible to carry out low temperature sintering by using ultrafine particles of tin oxide without using a binder of silica or alumina type, and to obtain a strong result. It is also an object of the present invention to provide a method for manufacturing a gas detection element that suppresses humidity dependency.

[0005]

A method for manufacturing a gas detecting element according to the present invention is a method in which a tin oxide fine particle having a particle diameter of 200 Å or more is used as a main component of a tin oxide ultrafine particle having an average particle diameter of 50 ∫ 800 It is one that is sintered at a temperature of ℃ or less.

[0006]

In the present invention, the ultrafine tin oxide particles serve as a binder to firmly fix the tin oxide fine particles and increase the mechanical strength. Further, since SiO ₂ and Al ₂ O ₃ are not used, humidity dependency is low.

[0007]

EXAMPLES The present invention focuses on the fact that the tin oxide ultrafine particles used in the gas detection element have excellent sinterability at low temperatures,
It can be used practically by mixing the tin oxide particles with a particle size of 200 Å or more, which has been used conventionally, with a binder containing ultrafine particles of ultrafine particles (average particle size of 50 Å) as the main component and sintering. The obtained mechanical strength is obtained.

An embodiment of the present invention will be described below.

The primary particle size of the hydrate obtained from the SnCl ₄ aqueous solution by the precipitation method is 20 Å or less.
Dehydrated and vapor-phase oxidized at 00 to 300 ° C, and pulverized to obtain tin oxide ultrafine particles having an average particle size of 50Å. About 30% of the total weight of tin oxide fine particles having a particle size of 200 Å or more is mixed with the tin oxide ultrafine particles, and the mixture is kneaded with water to form a paste. Next, this paste is applied on an alumina substrate having a platinum film heater and electrodes, dried, and sintered at 800 ° C. for 5 hours to obtain a target gas detection element.

An example of the gas detecting element thus obtained is shown in FIG. In FIG. 1, 1 is an insulating substrate such as an alumina substrate, 2 is a platinum film heater, 3 is an electrode, 4 is tin oxide fine particles having an average particle size of 200 Å or more, and 5 is an average particle size of 5.
Shows 0Å tin oxide ultrafine particles.

FIG. 2 shows an insulating substrate 1 made of alumina of 1.5 × 3.0 × 0.4 mm with a thickness of 0.1 to 0.2 mm as shown in FIG. 1 by the manufacturing method of the present invention. It is a characteristic view which shows the humidity dependence of the methane gas sensitivity of the gas detection element which apply | coated and sintered the tin oxide paste.

FIG. 3 is a characteristic diagram of the humidity dependence of the conventional gas detecting element. This gas detection element has a fine particle powder containing tin oxide as a main component in a paste of 1.5 × 1.5 × 4.
After embedding and molding the electrode wire coil on the mm chip, after drying,
It was obtained by immersing a 5-hexameric oligomer of tetraethyl orthosilicate in a solution of silicic acid hydrosol obtained by hydrolyzing it with hydrochloric acid, drying and sintering it at about 700 ° C. in the atmosphere. Note that the silicic acid hydrosol impregnated by immersion is sintered at about 700 ° C. in the atmosphere to form SiO 2.
₂ , it acts as a solidifying agent between tin oxide particles and becomes a robust and strong sintered body. FIG. 4 shows a partially cutaway perspective view of the gas detection element used in FIG. In this figure, 11 is S
nO ₂ sintered body, 12 and 13 are electrodes made of an Ir—Pd alloy wire, all of which are coiled to form SnO ₂ sintered body 11
It is isolated and buried inside.

2 and 3, the characteristic curve A is the gas detecting element of the present invention, and the characteristic curve B is the conventional gas detecting element, showing the dependence of the sensor output on the absolute humidity (mmHg) for 500 ppm of methane gas, respectively. It is a thing.

It can be seen from FIG. 2 that the sensor output (mV) of the gas detecting element of the present invention hardly changes even when the absolute humidity is 20 mmHg or less.

Further, in the gas detecting element manufactured according to the present invention, since the tin oxide fine particles 4 are firmly bonded to each other by the tin oxide ultrafine particles 5, the barrier of the contact between the tin oxide fine particles 4 is lowered, and the bonding element thereof is reduced. The sensitivity can be improved without increasing the specific resistance value of.

[0016]

As described above, the present invention has a particle size of 20.
Since 0 Å or more tin oxide fine particles are sintered at 800 ° C or less using a binder whose main component is tin oxide ultrafine particles with an average particle size of 50 Å, gas detection with high mechanical strength even at low temperature sintering An element is obtained, and its humidity dependence is small,
There is an advantage that there is little change with time in a high humidity atmosphere.

[Brief description of drawings]

FIG. 1 is a cross-sectional view showing a gas detection element manufactured according to the present invention.

FIG. 2 is a characteristic diagram showing humidity dependency of a gas detection element according to the present invention in methane gas.

FIG. 3 is a characteristic diagram showing the humidity dependence of a conventional gas detection element in methane gas.

FIG. 4 is a partially cutaway perspective view of the gas detection element used in FIG.

[Explanation of symbols]

 A characteristic curve B characteristic curve 1 insulating substrate 2 platinum film heater 3 electrode 4 tin oxide fine particles 5 tin oxide ultrafine particles

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[Procedure amendment]

[Submission date] November 29, 1991

[Procedure Amendment 1]

[Document name to be amended] Statement

[Name of item to be corrected] 0002

[Correction method] Change

[Correction content]

[0002]

_2. Description of the Related Art Conventionally, in the production of a gas sensing element of a metal oxide sintered body such as SnO ₂ or ZnO, a strong sintering temperature is set to maintain a gas-sensitive activity.
Since sintering at a high temperature of ℃ or higher cannot be performed, 8
Low temperature sintering below 00 ° C had to be performed.
For this reason, the sintering strength is remarkably weaker than that of ordinary ceramics, and the mechanical strength sufficient to withstand shock and vibration during general use cannot be obtained. Therefore, various proposals have been made to increase the mechanical strength of the gas detection element. On the other hand, are currently in commercial gas sensing elements are used as the silica coupling agent with an organic silicon compound, to be used is an alumina sol or a silica sol such as those of the other research and development stage.

Claims (1)

Claim: What is claimed is: 1. A method of manufacturing a gas detection element using a tin oxide sintered body, wherein tin oxide fine particles having a particle size of 200 Å or more are mainly composed of ultrafine tin oxide particles having an average particle size of 50 Å. A method of manufacturing a gas sensing element, which comprises sintering at 800 ° C. or lower using a binder.