JPH02280045A - Limiting current-type oxygen sensor and its production - Google Patents

Abstract

PURPOSE:To control the thickness of a conductor thin film with high precision and to obtain the oxygen sensor having a low working temp. by forming a porous electrode on a substrate having a gas diffusion hole by printing and forming the thin film of an ion conductor by vapor deposition. CONSTITUTION:The porous electrode 3 is applied on the substrate 1 having the gas diffusion hole 2 and a heater 7 and calcined, and a stabilizing zirconia thin film 4 is formed thereon by sputtering. A porous electrode 5 is formed on the thin film 4 in the same way as the electrode 3, and the peripheral part of the substrate 1 is sealed with a glass layer 6 to form an oxygen sensor. Since the porous electrode is formed by printing and the ion conductor thin film as the factor determining the working temp. of the sensor is formed by vapor deposition, the thickness of the thin film can be controlled with high precision, and an oxygen sensor having a low working temp. is obtained.

Description

[Detailed description of the invention] [Industrial application field]

The present invention relates to a limiting current type oxygen sensor and a method for manufacturing the same.

[Conventional technology]

A limiting current type oxygen sensor detects oxygen concentration by utilizing the fact that the amount of oxygen passing through a gas diffusion hole corresponds to the current using oxygen ions as carriers in an ionic conductor. This limiting current type oxygen sensor usually uses a stabilized zirconia chip as an ion conductor, has porous electrodes formed on both the front and back sides, and covers and seals the cathode electrode with a cap, and gas is diffused into this cap. Created by forming pores.

[The problem that the invention tries to solve! ] However, since the conventional limiting current type oxygen sensor does not operate sufficiently unless the temperature is high, there are problems such as the power consumption of the heater is large and it is difficult to convert it into a portable device powered by a battery. On the other hand, it has been known that the operating temperature can be lowered by making the ionic conductor thinner. Therefore, attempts have been made to achieve ultra-miniaturization and low-temperature operation by making the film thinner, but until now there has been no practical method for easily making the film thinner. In other words, the method of cutting and wrapping a stabilized zirconia chip to form a thin film (O,
It cannot be made thinner than 1 nvn. Further, according to the green sheet method, the thickness can be made up to 50 μIn, but that is the limit and it cannot be made thinner than that, and the manufacturing yield is poor at about 50%. An object of the present invention is to provide a limiting current type oxygen sensor that can operate at low temperatures by making the film thinner. Another object of the present invention is to provide a practical manufacturing method that allows a limiting current type oxygen sensor to be made into a thin film. [Means for Solving the Problems] In order to achieve the above object, a limiting current type oxygen sensor according to the present invention includes a porous electrode printed on a substrate having gas diffusion holes, and a porous electrode printed on a substrate having gas diffusion holes, and a An ionic conductor thin film and a porous electrode printed on the ionic conductor thin film are provided. The method for manufacturing a limiting current type oxygen sensor according to the present invention also includes a printing step of forming a first porous electrode on a substrate having gas diffusion holes, and a vapor deposition step of forming an ion conductor thin film on the electrode. , and a printing step of forming a second porous electrode on the ion conductor thin film.

[For production]

The ion conductor thin film is formed on the electrode by vapor deposition, and therefore can be easily reduced to a thickness of about 10 μIn. Therefore, it becomes a low temperature moving cow type limiting current type oxygen sensor. Further, the porous electrode is formed by printing, and only the ion conductor thin film is formed by vapor deposition. Therefore, the manufacturing process is easy and suitable for mass production.

【Example】

Next, an embodiment of the present invention will be described with reference to the drawings. First, as shown in FIG.
) Gas diffusion holes 2 with a diameter of about 10 μm are formed in advance on the substrate 1, and a heater 7 is formed on the back surface, and platinum particles are mixed with a suitable solvent and made into a paste on the surface of the substrate 1. Coat it. This step can be easily performed by screen printing, for example. Thereafter, it is fired at, for example, 900° C. for 30 minutes to obtain a porous electrode 3 having a thickness of about 5 μm. Next, as shown in FIG. 1B, sputtering is carried out using a sputtering device using stabilized zirconia (Zr02-8mol%Y2O3) as a target, and a layer of stabilized zirconia with a thickness of about 10 mm is deposited on the porous electrode 3 described above. (Zr02
-8 mo1% Y2O3) thin film 4 was formed. Furthermore, as shown in FIG.
μm forms which porous electrode 5. Finally, as shown in the first diagram, the peripheral portion of the substrate 1 was sealed with a glass layer 6. Specifically, a paste of glass particles mixed with a solvent was applied and fired at, for example, 900° C. for 30 minutes to form a dense glass layer 6. The limiting current type oxygen sensor made in this way operates at low temperatures because the stabilized zirconia is formed as a thin film with a thickness of 10 μIn. That is, when a voltage was applied between the electrodes 3.5 in this limiting current type oxygen sensor and the current was measured, voltage-current characteristics as shown in FIG. 2 were obtained. Note that this measurement was performed with this limiting current type oxygen sensor placed in the atmosphere at 200°C. This result shows that the operating temperature could be lowered by forming a single film. Further, as described above, only the stabilized zirconia thin film 4 is formed by vapor deposition, and the porous electrode 3.5 is formed by a coating process and a sintering process, so that it can be easily manufactured and has excellent reproducibility. Therefore, it has excellent mass productivity and can be manufactured at low cost. (Incidentally, it is also possible to form the porous electrode 3.5 by sputtering, but since it is normally deposited densely, a pretreatment process such as etching the surface is required before depositing. Furthermore, even if such a method is used, it is difficult to control the degree of porosity, and as a result, considering productivity and reproducibility, it is not viable as a practical mass production method. The zirconia thin film 4 is not limited to sputtering, but can also be formed by vapor-depositing stabilized zirconia by excimer laser, plasma CVD, or the like.

【Effect of the invention】

According to the limiting current type oxygen sensor of the present invention, the operating temperature can be lowered by making the film thinner. Further, the manufacturing method of the present invention requires fewer man-hours, the manufacturing process is easy, and has excellent reproducibility. In other words, the thickness of the electrode is unrelated to the temperature dependence of the limiting current type oxygen sensor.
Therefore, it can be produced roughly, and a printing process can be used. The thickness of the ion conductor thin film is a determining factor in the operating temperature, but since it is formed by vapor deposition, the thickness can be controlled with high precision. As a result, a limiting current type oxygen sensor having a sufficiently low operating temperature can be manufactured through an overall easy manufacturing process. ,Furthermore, since the deposition process is only performed once,,the rest can be done by the printing process.
It has excellent mass productivity and can be manufactured at low cost.

[Brief explanation of drawings]

FIGS. 1A, B, C, and D are cross-sectional views at each stage of the manufacturing process according to an embodiment of the present invention, and FIG. 2 is a graph showing an example of voltage-current characteristics. DESCRIPTION OF SYMBOLS 1... Substrate, 2... Gas diffusion hole, 3.5... Porous electrode, 4... Stabilized zirconia thin film, 6... Glass layer, 7... Heater

Claims (2)

[Claims] (1) A limiting current comprising a porous electrode printed on a substrate having gas diffusion holes, an ionic conductor thin film deposited on the electrode, and a porous electrode printed on the ionic conductor thin film. type oxygen sensor. (2) A printing process to form a first porous electrode on a substrate having gas diffusion holes, a vapor deposition process to form an ionic conductor thin film on the electrode, and a second porous electrode formed on the ionic conductor thin film. A method for manufacturing a limiting current type oxygen sensor, which comprises a printing process for forming a quality electrode.