JPH0830691B2 - Limit current type oxygen sensor - Google Patents

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a limiting current type oxygen sensor, and more particularly to a thin film type limiting current type oxygen sensor in which an ion conductor film and electrodes are formed by a thin film technique.

[0002]

2. Description of the Related Art A ceramic oxygen sensor using yttrium (Y) -stabilized zirconium oxide (ZrO2 --Y2 O3) as an ion conductor (solid electrolyte) has been known. In the bulk type ceramic oxygen sensor, a ZrO2 --Y2 O3 ionic conductor bulk is obtained by press molding and firing, and a Pt electrode having a catalytic action is formed by printing and firing a Pt paste.

In contrast to such a bulk type ceramic oxygen sensor, recently, in order to miniaturize, miniaturize, and mass-produce elements, a thin film type limit for forming a ZrO2 --Y2 O3 ionic conductor and an electrode by a thin film technique is applied. Current oxygen sensors have been proposed. This type of thin film type ceramic oxygen sensor is obtained, for example, by sequentially stacking a cathode electrode, an oxide ion conductor film, and an anode electrode on a substrate. In order to obtain the limiting current characteristic with the substrate side as the oxygen gas supply side in this thin film type ceramic oxygen sensor, a gas permeable substrate having a diffusion rate control of oxygen molecules is required as the substrate. As such a gas permeable substrate, for example, ZrO2
There is BN.

However, the gas permeable substrate as described above is
Since the pore size is as large as 0.1 to 0.2 μm, it is difficult to form a uniform film, and it is also difficult to provide a good diffusion rate controlling property. Therefore, using a dense substrate, the anode and cathode electrodes are turned upside down from the above-mentioned element,
It is also conceivable to form the gas diffusion layer by thin film technology so as to cover the cathode electrode.

[0005]

However, when a dense substrate is used and an anode electrode, an oxide ion conductor film, and a cathode electrode are laminated in this order, an ionic current flows to generate the anode electrode. Unless a discharge path for surely discharging the generated oxygen gas is secured, good limiting current characteristics cannot be obtained. The present invention has been made in view of such circumstances, and an object thereof is to provide a thin film type limiting current type oxygen sensor capable of obtaining excellent limiting current characteristics.

[0006]

In a limiting current type oxygen sensor according to the present invention, an anode electrode is formed on the entire surface of a substrate, and an oxide ion conductor film having a predetermined pattern is formed on the anode electrode. A cathode electrode is overlaid on the product ion conductor film in a state where the surface around the oxide ion conductor film is exposed, a gas diffusion layer covers the upper surface and the side surface of the cathode electrode, and It is characterized in that it is formed with its side surface exposed.

[0007]

The thin-film oxygen sensor according to the present invention has a structure in which the three-phase interface, that is, the interface between the ionic conductor, the electrode, and the atmosphere is sufficiently large on both the cathode side and the anode side. Therefore, the electrode reactions that contribute to the operation of the oxygen sensor proceed sufficiently on both the cathode and anode sides. Since the anode and cathode electrodes are formed by sandwiching the ion conductor film above and below, the electric resistance to the ionic current is also small. Since the anode electrode is formed on the entire surface of the substrate, the oxygen gas generated in the anode electrode is reliably discharged from the anode electrode portion where the oxide ion conductor film is not formed. From the above, a limiting current type oxygen sensor that operates at a relatively low temperature and is excellent in high-speed response can be obtained.

[0008]

Embodiments of the present invention will be described below with reference to the drawings. 1 (a) and 1 (b) are a plan view and a sectional view taken along the line AA 'of a thin film type limiting current type oxygen sensor according to an embodiment of the present invention. In this embodiment, as the dense insulating substrate 1,
It uses a ceramic substrate that can be cut. The surface of the insulating substrate 1 is mirror-finished. First, the Pt anode electrode 2 is formed on the entire surface of the substrate 1. Zr, which is an oxide ion conductor film, is formed on the anode electrode 2.
O2-8mol% Y2O3 film (hereinafter referred to simply as ZrO2-Y2O
3 film 3) is formed in a comb pattern.

ZrO2 --Y2 O3 film 3 is overlaid with Z
The Pt cathode electrode 4 is formed in a comb pattern in which the pattern of the rO2 -Y2 O3 film 3 is reduced. That is, the cathode electrode 4 is patterned around the cathode electrode 4 so that the peripheral surface of the ZrO2 --Y2 O3 film 3 is exposed. Furthermore, the cathode electrode 4
Of the gas diffusion layer 5 so as to cover the upper surface and side surfaces of the
It is formed in the same comb pattern as the rO2 -Y2 O3 film 3. The side surface of the ZrO2-Y2O3 film 3 is kept exposed.

A manufacturing process for obtaining such a structure will be specifically described. First, the Pt anode electrode 2 is formed on the entire surface of the dense substrate 1 by the sputtering method. Then ZrO
Comb-shaped ZrO 2 pattern using metal mask by sputtering method using 2-Y 2 O 3 ceramic target.
A 2-Y2 O3 film 3 is formed. Then, a Pt cathode electrode 4 is formed on the ZrO2 --Y2 O3 film 3 by a sputtering method using a metal mask having a window smaller than the upper metal mask.

Next, a gas diffusion layer 5 is formed by screen printing and firing so as to cover the cathode electrode 4. The screen printing mask is ZrO2-Y2O3
It is almost the same as the patterning mask of the film 3. Specifically, in this example, a paste obtained by mixing about 20 wt% of steatite ceramic powder with polysilazane, which is an inorganic polymer, was screen-printed, and the paste was mixed in a nitrogen gas atmosphere at 6
The gas diffusion layer 5 is formed by baking at 00 ° C. or higher for 10 minutes. As the material of the gas diffusion layer 5, an organic polymer such as polyimide or crystallized glass may be used instead of the inorganic polymer, and silicon nitride or the like may be used as the ceramic powder. Further, in the figure, the gas diffusion layer 5 covers the entire surface of the cathode electrode 4, but the cathode electrode 4 is naturally exposed at the terminal lead-out portion (not shown) of the cathode electrode 4.

In the device structure of this embodiment, ZrO 2 --Y
Since the 2 O 3 film 3 is sandwiched by the electrodes from above and below, the electric resistance to the ionic current is sufficiently low. Further, oxygen gas whose diffusion rate is controlled is supplied to the upper surface and the side surface of the cathode electrode 4 through the gas diffusion layer 4. Further, the anode electrode 3 is formed on the entire surface of the substrate and is made of ZrO2 --Y2
It is in good contact with both the O3 film 3 and the atmosphere. For these reasons, the oxygen sensor of this example is excellent in high-speed response and can obtain good limiting current characteristics at a relatively low temperature. As a result of performing oxygen gas measurement in an air atmosphere using a device that was actually prototyped, a clear limiting current characteristic with a sharp rise at 300 ° C. was obtained.

[0013]

As described above, in the thin film oxygen sensor according to the present invention, the anode electrode is formed on the entire surface of the substrate, and the oxide ion conductor film, the cathode electrode and the gas diffusion layer are laminated on the anode electrode in a predetermined pattern. The three-phase interface of the anode and the cathode is reinforced so that the limiting current characteristic with excellent high-speed response can be obtained at a relatively low temperature.

[Brief description of drawings]

FIG. 1 is a diagram showing a limiting current type oxygen sensor according to an embodiment of the present invention.

[Explanation of symbols]

1 ... Dense substrate, 2 ... Pt anode electrode, 3 ... ZrO2
-Y2O3 film, 4 ... Pt cathode electrode, 5 ... Gas diffusion layer.

 ─────────────────────────────────────────────────── ─── Continuation of the front page (72) Inventor Katsuaki Nakamura 1-5-1 Kiba, Koto-ku, Tokyo Fujikura Ltd. (72) Inventor Issei Ishibashi 1-1-5 Kiba, Koto-ku, Tokyo Shares In Fujikura, Ltd. (72) Inventor Yoshinori Kato, 1-5-1, Kiba, Koto-ku, Tokyo In Fujikura, Ltd. (56) Reference JP-A-63-259459 (JP, A)

Claims (1)

[Claims] 1. A dense substrate, an anode electrode formed on the entire surface of the substrate, an oxide ion conductor film formed in a comb pattern on the anode electrode, and an oxide ion conductor film oxidized to the oxide ion conductor film. A cathode electrode formed so as to overlap the surface around the ion-ion conductor film, and an oxide ion conductor film on which the cathode electrode is formed, covering the upper surface and the side surface of the cathode electrode, and forming an oxide. A limiting current type oxygen sensor, comprising: a gas diffusion layer formed with the side surface of the ionic conductor film exposed.