JPS60209159A - Gas detecting element - Google Patents

Abstract

PURPOSE:To detect gas selectively for miscellaneous gases such as alcohol by using SnO2 as a main component and adding at least >=0.01wt% Si or/and Al as an auxiliary component thereto. CONSTITUTION:A resistance value RA of a gas detecting element in air is almost constant up to 5wt% Si quantity to be added, but apt to decrease if said quantity is exceeded, said value RB in isobutane atmosphere decreases with the rise of >=0.01wt% Si quantity, but attains the min. value and is apt to remain on the same level if said quantity is exceeded. Said value RE in ethanol atmosphere is almost constant up to 5wt% Si quantity, but apt to decrease gradually if said value is exceeded. Consequently, by setting the adding quantity of auxiliary component Si for the main component SnO2 in said element at least >=0.01wt%, the sensitivity to the detecting gas is improved, and the selectivity effect is obtained.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a gas detection element for combustible gas such as inbutane gas.

Conventionally, gas detection elements for combustible gases such as inbutane gas have been made with 5n02 as the main component, and have been known to have the same sensitivity. However, it does not only improve sensitivity to flammable gases such as isobutane gas, but also improves sensitivity to miscellaneous gases such as alcohol, but has the disadvantage that it cannot detect specific gases.

The object of the present invention is to overcome all of these drawbacks and provide a gas detection element that has excellent sensitivity to flammable gases such as isobutane gas and can selectively detect miscellaneous gases such as alcohol. It is made of 8n02 as a main component, to which Sit and/or kl are added as subcomponents in an amount of at least 1% by weight of Sail O.

The figure shows the heating temperature 3 of a gas sensing element obtained by adding Si as a subcomponent to the main component S n 02 in the same amount as the glaze.
The blending amount of each 8i at 5o C, the electrical resistance value in air (hereinafter simply referred to as resistance value) RA, and the resistance direct value in the atmosphere of inbutane gas (mW 1800 ppm B)
It also shows the relationship between the resistance value fLE in an atmosphere with an ethanol gas concentration of 3600 ppm, and as is clear from the figure, the resistance value RA of the gas detection element in air is almost constant until the amount of Si added is 5% by weight. When the amount of Si added exceeds 5% by weight, the resistance value RB in an inbutane gas atmosphere tends to decrease.
The resistance value BE of the gas sensing element in an ethanol gas atmosphere decreases as the amount of Si increases, but when it exceeds 5% by weight, it reaches a minimum value and shows a flat tendency. It can be seen that although it is almost constant, it shows a gradual downward trend when it exceeds 5% by weight.

Therefore, the amount of addition of the subcomponent Si to the main component 5n02 is 0.
．． If the resistance value is less than 01% by weight, the resistance value B in the inbutane gas atmosphere and the resistance value 11[RE in the ethanol gas atmosphere are similar, so the selectivity for the detection gas is extremely low. ingredient 8i
By setting the amount of addition to at least 0.01% by weight or more, sensitivity improvement and selectivity effects with respect to the detection gas can be obtained.

In the gas detection element, the upper limit of the amount of the subcomponent S1 to be added to the main component 5n02 is the air resistance liRA, the isobutane gas resistance 1ii1 (B, and the ethanol gas resistance 1
It is desirable to set the content to 51% by weight so that the difference from 1II-E becomes noticeable. 1. From the viewpoint of reliability and safety for the gas detection element, it is more preferable that the addition range of the subcomponent Si is 0.5 to 2% by weight based on the main component 5n02.

Various amounts of A4 or S are added to SiO as a subcomponent.
i and A/1. 8i also when measuring the respective resistance values (LA, RB, RE) in air and in each gas atmosphere under the same conditions as above for the gas detection element obtained by adding each of
Similar results were obtained.

Next, the present invention will be further explained with reference to Examples and Comparative Examples.

Example Sn O4 water bath liquid was neutralized with aqueous ammonia to obtain a precipitated product, this precipitated product was filtered and calcined at a temperature of 570°C for 3 hours, and then pulverized to obtain a gas sensing element raw material consisting of 8n02. To this raw material, 8i fine powder was added and mixed in an amount of 1.5% by weight based on 8n02, and pure water was added to the mixture to form a paste. It was molded into a 1.0-inch shape and fired at a temperature of 600° C. for 1 hour to obtain a gas detection element KA.

Comparative example Pd was added to the main component S n 02 instead of the subcomponent Si.
．． A gas sensing element KB was obtained in the same manner as in the above example except that 5% by weight was added.

While maintaining the obtained gas sensing elements KA and KB at a temperature of 350°C, the resistance value RA in the air.

Resistance value R in an atmosphere with isobutane gas concentration of 1800 ppm
B. Measure each resistance value RE in an ethanol gas atmosphere, and calculate the logarithm 1iE to y of the resistance value KA in air.
Logarithm value 1 of RA and resistance value RB1RE in each gas atmosphere
The difference between o y RB and logarithm t o t RB was taken as the sensitivity characteristic of the gas detection element KA or KB to the detected gas. The results are shown in the table.

This table shows that the gas detection element KA of the example has improved sensitivity to isobutane gas compared to the gas detection system/child KB of the comparative example, and that the gas detection element KA of the example has improved sensitivity to isobutane gas compared to the gas detection element of the comparative example. It was confirmed that there was a significant difference in sensitivity to isobutane gas and ethanol gas, and that it had excellent selectivity to the detection gas.

As described above, the gas detection element of the present invention has at least 0.01% by weight of the subcomponents 8i and/or ktf added to the main component 8n02, so it has excellent sensitivity to flammable gases such as isobutane gas, and has excellent sensitivity to specific gases. It also has an effect of excellent selectivity.

[Brief explanation of drawings]

The figure shows the relationship between the weight percent of 98i added to the main component 5n02 and the resistance values RA, RB, and E. 2 people outside.

Claims (1)

[Claims] 5n02 as the main component, and S as a subcomponent.
A gas sensing element containing at least 0.01% by weight of i or/and kl.