JPS5847665B2 - gas sensing element - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a gas-sensitive element using an oxide semiconductor gas-sensitive body.

Conventional gas-sensitive elements using gas-sensitive bodies made of S n 0 2 -based oxide semiconductors usually have a small rate of change in resistance with respect to a certain concentration of gas, making it difficult to extract a gas detection output signal.

Alternatively, even if the resistance change rate is large, the change in resistance reaches the saturation value with a small amount of gas, making it impossible to distinguish between a gas leak caused by an accident or a gas leak caused by ignition during use of the appliance. It was inconvenient.

Furthermore, conventional methods have many drawbacks, such as being difficult to distinguish between liquefied petroleum gases such as propane gas and butane gas and H2, CO, etc., and causing false detection output signals due to reducing components such as cigarette smoke. was there.

The present invention improves the above-mentioned conventional drawbacks, and
99.85 to 20 mol 1%, Me 40g 0. 50 moles (However, as Me'203, SC203,L
At least one of a203 is 0 and Me≦03.
．． 05-30 mol% (Me203 is Ga203, B2
03 e I n2 03 p F e203 F k
l 2 03 t At least one of Cr203)
An object of the present invention is to provide a highly reliable gas-sensitive element by using a gas-sensitive body containing the following.

The gas-sensitive element according to the present invention detects gas by disposing a gas-sensitive body having the above-mentioned composition between a pair of electrodes and extracting a change in the electrical resistance of the gas-sensitive body as an electric signal using the electrodes.

The gas-sensitive element according to the present invention has a structure as shown in FIG. 1, for example.

This gas-sensitive element consists of a pair of metal wire electrodes 2 and 3 wound in parallel on the surface of a cylindrical ceramic insulating substrate 1, and a gas-sensitive material 4 coated and sintered around the wound portion. be.

In this example, one of the electrodes 2 and 3 is used also as a heater for heating the gas-sensitive body 4, but a separate heater may be provided.

The gas-sensitive element is manufactured, for example, as follows.

That is, Z n O = Me 2 0 s (M
e' is at least one of Sc, Y, La) Me≦
03 (Me2 is at least one of Ga, B, In, Fe, Al, and Cr) is weighed out in a predetermined composition ratio, mixed, and then water or a binder is added to form a paste, and the electrodes 2 and 3 are wound. After painting on the same part of the rolled volume and drying, 60
Fire at 0-800'C.

Regarding this firing, even in an electric furnace, electrode 2 or 3
The heater may be energized, and the atmosphere may be in the air.

The characteristic of resistance change with respect to gas concentration, which is the most remarkable feature of the gas-sensitive element of the present invention, is that as shown in FIG. The resistance value changes linearly.

However, the vertical axis in Figure 2 shows the resistance value in the absence of gas as Ro, and the resistance value in a C4H1o gas atmosphere as Rg, and the ratio of Rg to Ro as Ro/Rg. The axis shows the concentration of C4H1o gas.

Further, the characteristics of the resistance change of the gas-sensitive element of the present invention with respect to changes in gas concentration are shown in Table 1 for various examples, including reference examples.

In this table, the resistance value when the gas concentration is 0% at 25°C is R.
o, and C2H1o gas is 0. The resistance value at a concentration of IVol% is Rg O. The relationship when it is set to 1 is shown.

Further, the resistance value change of the gas-sensitive element of the present invention with respect to various reducing gases is shown in FIG.

In other words, hydrocarbons containing two or more carbon elements C (C2H6,
C3H8, C4H1o,...)), and the more carbon element C there is, the better the sensitivity, so this can be used to develop measuring instruments for hydrocarbon component analysis. Can be configured.

The gas-sensitive body used in the gas-sensitive element of the present invention may contain subcomponents such as catalysts within a range that does not impair the effects of the present invention.

For example, by adding Pt in an amount not exceeding 10% by weight to the entire composition, the sensitivity can be further improved.

Table 2 shows the resistance value Ro and resistance value change Ro/Rg of various examples when the gas-sensitive element of the present invention was manufactured by adding Pt to the composition of the gas-sensitive body.

Note that Ro and Rg are values measured by changing the gas concentration as described above.

The crude composition range of the gas-sensitive body of the gas-sensitive element of the present invention is that ZnO is 99%
．． Exceeds 85 mo/L/% and Me403 is 0. When Me 03 is less than 0.05 mol, the change in resistance value Ro/Rg0.1 due to adsorption and desorption of gas is small and difficult to detect.

Furthermore, even if ZnO is less than 20 molar, MeΔ03 is more than 50, Mei03 is more than 30, or pt added to these is more than IO, the change due to gas adsorption is still small, and the gas-sensitive material is Large temperature coefficient.

For these reasons, Z can be used as a gas-sensitive body.
99.85 to 20 mol% of nO, 0.1 to 0.1 of Me'0
50 mol% (Me' is at least one of ScY, La), 0.05 to 30 mol% (M
e2 contains at least one of Ga, B, In, Fe, 1'J, and Cr.

As a representative example among the examples shown in Table 2, for Example 128, the resistance change due to room temperature change is shown in FIG. 4, and the resistance value change due to heater voltage change is shown in FIG. 5. As shown in FIG. 6, all of them exhibit excellent characteristics.

In addition, ZnO, Mem used for manufacturing the gas-sensitive body of the present invention
o3 (however, Me" is at least one of Se, Y, La), Me Todoro 03 (however, Me2 is Ga,
At least one barrel of B, In, Fe, and Cr may be a compound that converts into an oxide upon heating, such as a hydroxide, carbonate, oxalate, or nitrate.

Also, pi is H2PtCl6・H20, NH4PtCl6
, K2PtCl4, K2PtCl6, Na2PtCl, etc. may also be used.

[Brief explanation of the drawing]

FIG. 1 is an external perspective view showing the gas-sensitive element of the present invention, and FIG. 2 is the gas concentration (VOl) of the gas-sensitive element of the present invention and the conventional example.
%) is a characteristic diagram showing the resistance change (Ro/Rg), and FIG. 3 shows the gas concentration t! A characteristic diagram showing resistance change (Ro/Rg) with respect to −(Vol%), FIG.
FIG. 5 is a characteristic diagram showing the resistance change rate (ΔR/R20°C) with respect to room temperature change based on the resistance value (R20°C) of , and FIG. 5 is a characteristic diagram showing the resistance value with respect to heater voltage change according to the embodiment of the present invention. FIG. 6 is a characteristic diagram showing the change in resistance value over time after gas injection in the embodiment of the present invention. 1... Insulating base, 2, 3... Heater/electrode, 4... Gas sensitive body.

Claims (1)

[Claims] 1. A gas-sensitive element comprising a pair of electrodes and a gas-sensitive body provided between the electrodes, wherein the gas-sensitive body is...
, ZnO at 99.85 to 20 mol, Me M 0
3 to 0.1 to 50 molar ratio (however, Me403 is SC
2 03 t Y2 03 p La 2 03) and Me 03 from 0.05 to 30
Mol ratio (however, M e '> 0 3 is Ga203
1 B203, In2os, Fe203, Al
203, Cr203).