JPH04152258A - Ozone sensor - Google Patents

Abstract

PURPOSE:To provide a high reliability sensor consisting of a cheap and practical material by furnishing a pair of electrodes on a base board, and installing between the pair a film-form gas sensitive body chiefly containing In oxide and Sn oxide. CONSTITUTION:Over a base board 1 provided previously with a pair of Pt electrodes 3, a film is formed by the screen print method using an ink prepared with main components as 2-ethylhexanates of In and Sn, and the resultant is baked at 500 deg.C to accomplish a film-form gas sensitive body 2 consisting of In oxide (95wt.%) and Sn oxide (5wt.%). This achieves a high reliability sensor element in small size and light weight, wherein the sensitivity and response to ozone excel even in low temp. range.

Description

[Detailed Description of the Invention] Industrial Application Fields The present invention relates to ozone generation, ozone sensor used for ozone concentration control and ozone detection in ozone-using equipment, and conventional technology. Ozone exhibits a strong oxidizing effect. Although ozone is used in many fields such as water supply and sewage facilities, medical facilities, food industry, etc., ozone is harmful to the human body even in very small amounts. In such situations, it is necessary to measure ozone concentration.Although redox titration, spectrophotometry, ultraviolet absorption spectroscopy, etc. are commonly used for detection, there is a simpler method for measuring ozone concentration. Although a sensor element using Ingot has been proposed as a sensor element, the problem to be solved by the invention is, however, the ozone measuring device that has been used in the past is generally complicated, requires complicated operation, and is expensive, so it is not easy to use. In*Q was proposed as a material for a simple sensor, even though it has the disadvantage of not being able to
s is chemically unstable and had problems with long-term stability.The present invention solves the above problems and provides an ozone sensor made of a practical material that can be a highly reliable and inexpensive sensor. Objectives and Means for Solving the Problems In order to achieve the above objectives, an ozone sensor 41 of the present invention is provided.
The ozone sensor according to the present invention has a structure in which a pair of electrodes is installed on a substrate, and a film-like gas sensitive material mainly composed of In20s and Snow is provided between the pair of electrodes. 5
A material mainly composed of nOs is used as the gas sensitive body.It has excellent gJt response to ozone even in a low temperature range, and has high reliability.It also allows the sensor element to be made smaller and lighter, making it easier to handle. in,
In addition, it is possible to provide a low-cost ozone sensor.Embodiments Hereinafter, embodiments of the present invention will be explained based on the accompanying drawings. Fig. 1 is a top view of an embodiment of the ozone sensor according to the present invention. Also, Figure 2 is a cross-sectional view taken along the line A-A' in Figure 1. In Figures 1 and 2, l is an alumina substrate (3x8xO, 5mm) and 2 is In5ot and Sn.
3 is a pair of platinum electrodes (width 1 mm) formed on the substrate L in advance.
Example 1 In is deposited on a substrate I on which a pair of platinum electrodes 3 are formed in advance.
1! was produced by a screen printing method, which is one of the wet film forming methods, using an ink prepared mainly from 2-ethylhexanoate of Sn and 2-ethylhexanoate. ! L Baked at 500℃ i 1aQs
Example 2 A pair of platinum electrodes 3 were formed in advance. In on the substrate 1
11L was produced by a coating method, which is one of the wet film forming methods, using a coating solution containing chlorides of Sn as starting materials and baked at 500°C to produce 20g of In (95wt%) and Snow (5wt%).
Membrane-like gas sensitive body 2 consisting of (3 x 4 m @ thickness 2
Comparative Example 1 A film with the same composition as in the example was prepared by RF magnetron sputtering, which is one of the dry film forming methods, on a substrate l on which a pair of platinum electrodes 3 had been formed in advance. Comparative example 2 in which an ozone sensor equipped with a gas sensitive body was prepared. Pre-prepared I neos and Snow powders (particle size of each about 1 μm) were mixed at a ratio of 95+5 (wt%), prepared and sintered. The 2 x 4 x 1 mm sintered ozone sensors were fabricated. The substrate and electrode shape and dimensions in Example and Comparative Example 1 were all the same. The response characteristics of these ozone sensors to ozone were measured. Change in electrical resistance of the ozone sensor when a quartz glass measuring tube with a fixed sensor is placed in an electric furnace, the temperature is controlled to a predetermined value, and air and air containing 3 ppm of ozone are alternately brought into contact with the ozone sensor. The results are shown in FIG. 3, where ReI is the electrical resistance of the ozone sensor 20 seconds after contact with air containing ozone, R11 is the electrical resistance of the ozone sensor in air, and Raze/Re is the sensor sensitivity. From this result, screen printing method
An ozone sensor equipped with a film-like gas sensitive material produced by a wet film-forming method such as a coating method has excellent gas sensitivity to ozone. It has been found that an ozone sensor equipped with a gas sensitive body exhibits gas sensitivity at high temperatures, and that sufficient sensitivity cannot be obtained at practical temperature levels.
This is thought to be because the film is more porous than the film produced by magnetron sputtering, so the surface area of the sensitive body is larger, and gas diffusion and reaction occur quickly even at low temperatures. Although it is considered that the response characteristics are poor because of the low temperature, it is very advantageous in practical terms that an ozone sensor equipped with a film-like gas sensitive material made by screen printing or coating has a gas sensitivity peak on the low temperature side. In the case of an ozone sensor made of a sintered body (Comparative Example 2), it became clear that almost no sensitivity to ozone could be obtained. Although it was thought that sensitivity could not be obtained because the ozone sensor did not have any influence, the response was measured using the ozone sensor of Example 1.
people, 2000 people, 5000 people, 80
00 people and 5 types of LAM The response time to find the relationship between the thickness and the response time is the 90% response time (t・-) when the air containing 3 ppm of ozone is brought into contact, f, and the temperature of the ozone sensor is The results are shown in Figure 4.9 From these results, it can be seen that it is possible to greatly improve the response by reducing the thickness of the gas sensitive material.Example 3 By screen printing method 0.1 wt% of Pd was added to the formed film-like gas sensitive bodies (thickness of 1000 and 5000).
Create an ozone sensor containing the added ozone and use the same method as above
The response was measured at 50°C and the results are shown in Figure 5. As a result, it was revealed that the response was improved by adding Pd. This is thought to be due to the increase in the surface reaction rate due to Pd. In2rt instead of the film-like gas sensitive material made of 5n02
An ozone sensor equipped with a film-like gas sensitive body consisting of
Regarding Comparative Example 3), the measurement method for measuring the change in sensitivity over time was to leave the ozone sensor in an air atmosphere at 400°C, take it out every 200 hours, and measure the change in electrical resistance at 150°C using the same method as above. Sensitivity (R
The change in Im/R*) over time was determined. The results are shown in Figure 6. As a result, the ozone sensor equipped with a film-like gas sensitive material made of ne Qs had a change in characteristics. It has become clear that the ozone sensor according to the present invention has extremely stable characteristics thermally, and as has been clarified through nine or more examples.还 In the example, the force strength was shown when the weight ratio of Intos and 5nOt was 95:5.Almost similar results were obtained when the weight ratio of Intos and 5nOt was 95:5.Also, in the example, a screen printing method was used as a method for producing the gas sensitive body. Offset printing, other printing methods, and spin code methods can also be used, and in either case, it is possible to create an active gas sensitive material with a high surface area. The starting materials for the gas susceptor are not limited to those in the examples, but alkoxides, nitrates, and other materials suitable for the gas susceptor manufacturing method can be appropriately selected and used.Furthermore, noble metals or metals other than Pd can be used as additives. It is also possible to use oxides, and the structure and configuration of each part of the sensor, as well as the substrate material and electrode material, can be freely designed or used as long as they do not go against the spirit of the invention. Sensor 1 has excellent gas detection characteristics, excellent thermal stability, and is small, lightweight, and inexpensive.It is suitable for applications such as ozone concentration control and ozone detection in ozone generators and ozone utilization equipment.

[Brief explanation of the drawing]

Fig. 1 shows the top surface of an embodiment of the ozone sensor according to the present invention. Fig. 2 shows the same isolation plate. Fig. 3 shows the temperature characteristics of the sensor sensitivity. Fig. 4 shows the responsiveness of the sensor. P
Figure 6 shows the effect of d addition on the responsiveness of the sensor. Akira Haka 2 people - Shirayoshi Kameyu (electrode) Part! Front view? Figure 1 Dcn Figure film thickness (,4) Figure film thickness (〆)

Claims (3)

[Claims] (1) A pair of electrodes is provided on the substrate, and indium oxide (In_2O_3) and tin oxide (SnO) are placed between the pair of electrodes.
_2) An ozone sensor characterized by being provided with a film-like gas sensitive body mainly composed of _2). (2) The ozone sensor according to claim 1, wherein the film-like gas sensitive body is formed by a wet film forming method. (3) Starting materials include indium (In) and tin (Sn).
3. The ozone sensor according to claim 2, wherein the ozone sensor uses either an organic metal compound or an inorganic acid salt.