JPS58123447A - Gas detecting element - Google Patents

Abstract

PURPOSE:To provide a small size and high reliable gas detecting element which has a fast answering speed and a high output voltage, by a method wherein electrode materials different in a type are applied to both sides of a sintered material with a specified texture being used as an oxygen ion conductive material, and the sinterd material and the electrode are covered with a porous protecting layer. CONSTITUTION:An oxide or a carbonate, being a raw material of a magnetic composition, is Y2O3, WO3, ZrO2 with a purity of not less than 99.8%, which are respectively weighed so that they are brought to 0.5<=x<=1.0 by a chemical formula of Y6(WxZr1-x)2O15, they are mixed by a ball mill for 46hr togetherwith pure water, and after the mixture is filtered and dried, it is temporarily burned at 1,200 deg.C for 2hr, and it is then repulverized by an attritor. A 5% alcohol liquid is then added to granulate it, the granulation is press-molded 10mm. in diameter and about 5mm. in length, and after it is sintered at 1,200 deg.C for 1hr, it is cut to 0.5mm. in thickness. After a platinum electrode 1 is baked to one side of a sintered material 3, a silver electrode 2 is baked to the opposite side thereof, and a lead wire is connected thereto. A glass paste is further applied as a porous protecting layer 6, the work is baked at 500-700 deg.C to produce a glass detecting element. The element has a fast answering speed to hydrogen, isobutane, or the like is also excellent in a returning property, is approximately linearly increased in a value of an electromotive force with the increase in gas concentation, and has an excellent selectivity to gas.

Description

DETAILED DESCRIPTION OF THE INVENTION When the present invention is placed in a reducing gas or a combustible gas, an electromotive force is generated depending on the gas concentration, and the gas sensing element K11I detects the gas.

Conventional solid electrolyte materials such as tMA-based gas sensing elements include calcia (CaO) and yttrium (Y2O).
1) Solid electrolyte material sensors using stabilized zirconia (ZrO, ) are well known. As shown in FIG. 1, electrodes 1 and 2 made of porous platinum 1 are applied to the inside and outside 111 of a pipe 3 made of a solid electrolyte, and leads are applied! It has a structure with I4°4. Measurement TIc of monoxide concentration is zrO, the pipe is placed in the gas to be measured I! Also, the relationship between the electromotive force generated between electrode 1 and electrode 2 of the pipe at this time and the oxygen partial pressure is 11
) expression Nernos! It is given by the relational expression n.

w=(RT/4v)In (pci”, '/pd'!:
) (1) PO (!l and PO\) are the partial pressures of oxygen in the gas in which electrode 1 and electrode 2 are placed, respectively. Therefore, the oxygen concentration cell in the gas to be measured can be estimated from the value of the electromotive force generated based on the difference in oxygen partial pressure inside and outside the solid electrolyte pipe.

Oxygen concentration meters using this type of oxygen concentration battery can be used, for example, to measure oxygen concentration in automobile exhaust gas.

(2) It is used for applications such as controlling the amount of dissolved oxygen in molten steel.

However, the above-mentioned conventional solid electrolyte materials and
, 11-The single gas detection element used has various drawbacks as follows.

If the temperature is not higher than that, it will not be possible to obtain a dense magnetic pipe, and the manufacturing will be easy. The zirconia pipe itself had the disadvantage of being weak, causing cracks and deterioration of characteristics.

In addition, 3 elements aK known gases such as air or oxygen v
Since it is necessary to supply the -1 electrode part as an i quasi-gas, the shape becomes large and the size is reduced.

There were also some drawbacks. Furthermore, since the temperature of the gas to be detected must be several hundred degrees, its use is naturally limited.

In order to eliminate the above-mentioned drawbacks, an element having a structure as shown in FIG. 2 (3) has been proposed. In other words, stabilized zirconia disk 3cD front and back KP paste! Printed and baked t electrodes 1 and 2 [Also, a catalyst layer 5 and an electrode lead wire 4t were provided on the -1 electrode. It is true that such a structure makes it easier to miniaturize the device. However, the time required for the output voltage to reach a certain value after gas introduction, that is, the response speed, is extremely slow and requires a time of 5 minutes or more.11 There is also the problem that the output voltage decreases due to deterioration of the catalyst layer.

The purpose of non-invention is to eliminate these drawbacks: 1. The objective is to provide a gas detection element that is small in size, has a fast response speed (high % output voltage, and is extremely reliable).

The gas detection element of the present invention is ""Xzr 1-X)xO+
The porcelain composition is expressed by the chemical formula s, and is expressed in the range of α5≦X≦10. Different electrode pastes were baked to form electrodes 1 and 2, and 4 tons of lead wires were attached to the electrodes, which were further porous. This will be explained in detail based on the following.

Y, σ Zs -x, ) 20 , @ The oxide or carbonate used as a raw material is an oxide with a purity of 99.8% or more.
a Y 4 (wxzr
1-X)201S Weigh out a predetermined amount of each so that X-0,8 will die, mix with M water in a ball mill for 46 hours, over-dry once, and then calcinate at 1200℃ for 2 hours. After that, it was re-pulverized using a raikai machine, then granulated by adding a 5% polyvinyl alcohol solution, and press-molded to a diameter of 11) and a length of approximately 511IIIK.
After sintering at 1200°C for 1 hour, it was cut to a thickness of 9.5 mwa.

After baking one piece of NK platinum electrode as shown in Figure 3, a silver electrode was baked on the opposite side to make II-do-IIt-connection.

Glass paste as the porous protective layer 6! Coating, 500
Baked at 700°C.

Wind the heater 5 with a constant length of 1" as shown in Figure 4 (5
) Attached quartz pipe 7t-sample 0ffl [tIK300℃
A sample prepared using the above O method was heated to ~400°C, and a gas of known concentration was flowed at approximately 100 CC for 1 minute into a quartz pipe. , the voltage ti1 induced in the sample
11 - The results are shown in Figures 5 to 7.

Figure 5 shows the electromotive force induced in the sample when a gas mixture of 3000 ppmQ of imbutane in air was poured into a quartz pipe heated with a heater so that the sample temperature reached 400°C. The induced voltage reaches its current value within 5 seconds.
'OSC was reached and the response speed was sufficiently fast. It was found that the recovery performance after switching the gas to only air was good, and the recovery was achieved within 1 minute, which was sufficient for practical use.

Figure 96 shows H2III! ! 1″ isobutane (i-
C4I (,.) III This is a tube that measures the electromotive force when changing the mixture ratio to air.・The value of electromotive force increases as the gas concentration increases.・But it depends on the type of gas. This also shows that there is a difference in [, and selectivity to gas can be obtained.

(6) 1 The concentration required for the detection of flammable gas is explosive T-
It is said to be less than 1/100 of the limit lA. For isobutane this value ranges from approximately 100 ppn to 5000 ppn.
It can be concluded that the device of the present invention has an output voltage of approximately 50 mV or more for this 8f isobutane a degree, and is sufficiently effective.

Furthermore, if the same electrode materials are used for section 1 and electrode 2t shown in Figure 3, the output voltage will be 10 mV or less, and the characteristic 1 that is effective as a gas detection element will not be exhibited. Even when the other electrode was made of palladium, it showed good characteristics as in the case of platinum, i.e., 7! Depending on the combination of electrode materials selected,
Figure 7 shows the composition of the sintered body of zirconium dioxide (ZrO2) and tungsten oxide (WO!) in the gas sensing element of the present invention.
) by changing the ratio of: Ilryocarbon (Co) k 3
Gas detection element output 1 for air containing 000 ppn
The method for detecting the motive force value of 10 mV or less, which indicates the pressure, is as follows:
7) The compositional surplus, etc. will increase. Therefore, it is desirable that the electromotive force be as large as possible, and 50 mV or more is necessary.

'ft-70' Y4 (WxZ
r,−,),0. .

In the magnetic dust composition represented by n, the range of the blending ratio X of zirconium oxide and tungsten oxide is preferably 0.5≦X≦1.0.

The table below shows how the uninvented gas sensing element can be measured from room temperature to
Put it into an electric furnace kept at 00℃, hold it for 5 minutes, take it out to room temperature again, leave it for 20 minutes, and try the temperature cycle! ! The rate of change of the output voltage after repeating up to rsoo times is shown.

The conventional element #'i in Table 1 was fabricated using Zir(8) Conia (ZrO2)t'' stabilized with calcia (Cab) with the structure shown in Figure 2.Test results ,
In conventional devices, the solid electrolyte and the electrode or between the electrode and the catalyst layer are separated by a temperature cycle or '! It has been found that cracks may occur and the output voltage will drop significantly. -7 Does the uninvented device have stable characteristics with almost no decrease in output voltage V? It shows.

Furthermore, the porous protective layer was effective in reducing the change in electromotive force over time and stabilizing the device. In the gas sensing element of the present invention, the temperature cycle test M of the device not provided with this protective layer was comparable to that of the conventional element. It was found that it has the effect of increasing the adhesive strength with the electrolyte.

As described above, it is clear that the uninvented gas sensing element is small, easy to sinter, resistant to temperature cycles, has sufficient stability, and exhibits practically useful performance in response speed output voltage t4.

In the non-example, a combination of silver and platinum and a combination of silver and palladium was shown as the electrode material, but other combinations (9) may be used. Similar properties can also be obtained with platinum.

(10)

[Brief explanation of the drawing]

Figures 1 and 2 are diagrams showing the structure of Yokomai's waste detection confectionery. , FIG. 3 is a bottom diagram of the structure of the gas detection element of the present invention. FIG. 4 is a diagram showing an apparatus for measuring characteristics of a dregs detection element according to the invention. Figures 5 and 11g6 are custom-made diagrams of the gas detection element of the present invention. FIG. 7 is a T diagram showing the relationship between the ml ratio and the electromotive force of the 1g single-body electrolytic sintered body used for the uninvented sword detection element number. In Figure 1, 5, 1.2 is platinum'1 pole, 3 is the same seat pipe, and 4 *4 is! It has a J-do flavor. In FIG. 2, numerals 1 and 2 are platinum electrodes, 3 is a sintered M body made of solid ingot, 4 and 4 are leads, and 5 is a catalyst layer. In Figures 3 and 4, 1.2 is the '-pole, 3 is the condenser-resolver, 4, 4-lead-16 is the porous protection, j is the heater, and 7 is the quartz pipe. be. In Figure 6, if you are 8, the samurai who is standing at 9, will be paying attention to water.
Illustration penalty Figure 2 Figure 3 Figure 4

Claims (1)

[Claims] In a gas detection element in which electrodes are provided on both sides of a sintered body that performs oxygen ion conductivity, and lead wires are attached to the electrodes, Y4 (wxz, -x)20,
5 (However, α5≦x<1.0)? Show me! 3 le 1111
A conductor (on conductor) is used, and tubes of different types of electrode materials are provided on both sides of this sintered body, and the sintered body and the electric conductor are
A gas sensing element characterized by being coated with a porous protective layer.