JPH0526832A - Oxygen sensor - Google Patents

Abstract

PURPOSE:To obtain a room-temperature-actuated type oxygen sensor having a small size and light weight. CONSTITUTION:After a detecting section 11 is formed by patterning a layered substance composed of CuFeTe2, formed on a polyimide film 10 by a thin film forming technique, platinum electrodes 12 are formed on both sides of the section 11. Since the oxygen sensor thus formed is formed on the polyimide thin film having excellent flexibility, the weight of the sensor becomes extremely light and the size of the sensor becomes small.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an oxygen sensor which can be operated at room temperature by using a layered substance having a two-dimensional crystal structure and having intercalation characteristics, and in particular, has been made smaller and lighter. Regarding the oxygen sensor.

[0002]

2. Description of the Related Art A layered substance is a substance having a two-dimensional structure such as mica, graphite, transition metal dichalcogenide, etc., in which atoms are strongly bound by covalent bonds or ionic bonds. In addition, the layers are connected by weak van der Waals forces, and it is necessary to insert certain atoms and molecules into this van der Waals gap without destroying the layered structure. You can This phenomenon is intercalation, and the insertion substance at this time is called intercalant. Furthermore, the reversible outflow of intercalants is called deintercalation.

When a layered substance made of CuFeTe _{2 is} used as a sensing section and electrodes are electrically connected to the sensing section to form a sensor, the resistance between the sensing section between the electrodes and the oxygen gas concentration are different. Good reproducibility in relationships. For this reason,
This sensor can be applied as an oxygen sensor.

In the case of a conventional oxygen sensor, for example, an oxygen sensor using stabilized zirconia (ZrO ₂ ) which has been put into practical use for controlling exhaust gas of automobiles, or an oxygen sensor using TiO ₂ , the temperature is 350 ° C. or lower. Although it does not operate at low temperature, the oxygen sensor using this layered material is capable of low temperature operation at about 100 ° C at present, and is the most promising for developing an oxygen sensor that operates at room temperature. It is a thing.

There is another type of room temperature oxygen sensor, which is of the galvanic cell type. Since it basically utilizes chemical changes, it may be caused by factors such as mass transfer and electrolyte consumption. However, it has a short life. Recently, in order to improve the life of the galvanic cell type oxygen sensor, the diaphragm and the electrolyte to be used have been devised, but on the contrary, this causes another drawback that the response becomes slow. Further, in the case of the galvanic battery type oxygen sensor, if it is downsized, it is a consumption type sensor, so that it has a drawback that the life becomes extremely short.

On the other hand, the oxygen sensor using the layered substance as a sensing portion does not have such a defect because it is not a consumption type unlike the above-mentioned galvanic cell type oxygen sensor.

FIG. 2 is a sectional view showing an oxygen sensor using a conventional layered material. This oxygen sensor is CuFeTe
The single crystal of No. ₂ was prepared by the Bridgman method, and the obtained single crystal mass was pulverized into a fine powder state, and then molded by the uniaxial pressure pressing method into a plate-like shape, which was used as the sensing unit 1. The electrodes 2 and 3 are formed on the front surface and the back surface of 1, respectively,
It is manufactured by connecting the wiring 4 to the wiring 3.

The sensing part 1 made of this layered substance uses oxygen as an intercalant, and this intercalant causes intercalation or deintercalation depending on the change in oxygen concentration, and the electrical resistivity changes. Then, the oxygen concentration can be detected.
That is, if the calibration data between the oxygen concentration and the electrical resistivity is obtained in advance, the oxygen concentration when the oxygen partial pressure changes can be obtained from the change in the electrical resistivity.

[0009]

However, in the above-mentioned conventional oxygen sensor, in order to make the characteristics such as sensitivity and response practically sufficient, it is necessary to increase the effective surface area into which oxygen is inserted or released. There is. For this reason,
The conventional oxygen sensor has a drawback that it is difficult to reduce the size and weight.

The present invention has been made in view of the above problems, and an object of the present invention is to provide a room temperature operation type oxygen sensor which can be reduced in size and weight.

[0011]

An oxygen sensor according to the present invention comprises a film made of an organic material, and a sensing section made of a layered substance having a two-dimensional crystal structure formed on the film by a thin film forming technique. It is characterized by having a pair of electrode portions which are in contact with the sensing portion and are arranged at appropriate intervals.

[0012]

In the present invention, a thin film of a layered substance such as CuFeTe ₂ is formed on a film made of an organic material. A film made of this organic material is typified by a polyimide film, as compared with an insulating ceramic film,
Since it is excellent in flexibility and has sufficient strength even if it is extremely thin, there is an advantage that it can be made thin and lightweight. In addition, since a film made of an organic material such as polyimide has good reactivity with a metal, CuFeTe ₂
The crystal layer can be easily formed with high adhesiveness, and the heat resistance is excellent.

The layered substance which is the sensing portion is required to have a contact area with the atmospheric gas (oxygen gas) as large as possible, but the layered substance formed by the thin film forming technique has a low orientation, so that the width can be as wide as possible. By making it narrower and longer, the contact area between the layered material and the atmosphere gas increases,
The effective area can be made extremely large.

As described above, according to the present invention, since the layered substance is formed on the organic film by the thin film forming technique, the contact area with the atmosphere is large and the effective area is extremely large, so that the sensitivity and response are extremely good. ..

[0015]

Embodiments of the present invention will be specifically described below with reference to the accompanying drawings.

FIG. 1 is a schematic sectional view showing an oxygen sensor according to an embodiment of the present invention. As shown in FIG. 1, a sensing portion 1 made of a layered material such as CuFeTe _{2 is} patterned on a polyimide film 10 by a thin film forming technique such as sputtering. Then, the platinum electrode 12 is similarly pattern-formed by the thin film forming technique on the polyimide film 10 at the position where the sensing unit 11 is sandwiched in plan view. The electrodes 12 are connected to a resistivity measuring device (not shown) between the electrodes 12 by appropriate wiring.

In the oxygen sensor thus constructed, oxygen (intercurrent) is intercalated between the sensing portion 11 and the atmosphere via the surface of the sensing portion 11, as indicated by the arrow in FIG. The resistivity of the sensing unit 11 changes due to the curling and deintercalation. There is a good reproducible correlation between the oxygen concentration of the atmosphere and the resistivity. Therefore, by obtaining a calibration curve between the oxygen concentration and the resistivity in advance, it is possible to obtain the oxygen concentration based on the calibration curve from the measurement result of the resistivity at the time of measurement.

In this embodiment, since the sensing portion 11 is a thin film, the area itself in contact with the atmosphere (ie, the effective area) is extremely large, but it is itself lightweight. Further, since it can be formed by a thin film forming technique, its shape can be miniaturized. Therefore, according to this embodiment, a lightweight and small oxygen sensor can be obtained. When the electrode is formed by a printing method, generally, the structure of the electrode becomes porous in the firing process. This improves the air permeability of the electrodes, further increases the contact area between the sensing portion and the atmospheric gas, and improves the response as a sensor. However, the electrode is not limited to the porous one. However, the electrode needs to have good adhesion to the sensing section and the film made of an organic material.

Next, the result of actually manufacturing the oxygen sensor of this embodiment and examining its characteristics will be described. First, CuFeTe is formed on a polyimide film 10 having a thickness of 25 μm.
_{The second} thin film (sensing unit 11) was formed using a sputtering device. Next, the electrode 12 was formed by sputtering platinum. As a result, in the obtained oxygen sensor, the thickness of the sensing portion 11 which is a layered substance is 2 μm,
The length is 1.0 mm, the thickness of each electrode is 2 μm, and the length is
It is 1.0 mm.

As a result, the obtained oxygen sensor was much smaller and lighter than the conventional oxygen sensor in spite of the sensitivity and the response being equal to or better than the conventional oxygen sensor. It was

In this embodiment, CuFe is used as the layered material.
Although the oxygen sensor using Te ₂ has been described, it goes without saying that the present invention is not limited to this and can be applied to oxygen sensors using other layered substances.

[0022] As layered material, outside the CuFeTe _2, there is ZrSe ₂ and NbSe ₂ or the like. Further, as the insulating film, in addition to the polyimide film of the above embodiment, there are films made of organic materials such as PET, PBT, polypropylene, polyethylene and nylon.

[0023]

As described above, according to the present invention, an oxygen sensor using a layered substance, which is attracting attention as an oxygen sensor capable of operating at room temperature or relatively low temperature, can be made extremely small and lightweight. .. Therefore, the present invention significantly contributes to the expansion of applications of the room temperature oxygen sensor,
It makes a great contribution to the improvement of oxygen concentration measurement technology.

[Brief description of drawings]

FIG. 1 is a schematic cross-sectional view showing an oxygen sensor according to an embodiment of the present invention.

FIG. 2 is a schematic cross-sectional view showing a conventional oxygen sensor.

[Explanation of symbols]

 1, 11; Sensing part 2, 3, 12; Electrode 10; Polyimide film

Continued Front Page (72) Inventor Kazumi Hirakawa 1-38 Nakao 1-38 Nakao, Minami-ku, Fukuoka-shi, Fukuoka

Claims (1)

Claim: What is claimed is: 1. A film made of an organic material, a sensing unit made of a layered material having a two-dimensional crystal structure formed on the film by a thin film forming technique, and a sensing unit in contact with the sensing unit. An oxygen sensor having a pair of electrode portions arranged at an appropriate length.