JPH04152259A - 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 Co 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 component as alkoxide of Co, and the resultant is baked at 500 deg.C to accomplish a film-form gas sensitive body 2 consisting of Co oxide. This achieves an ozone sensor in small size and light weight having excellent thermal stability, wherein the sensitivity and response to ozone are also excellent in the low temp. range.

Description

[Detailed Description of the Invention] Industrial Application Field The present invention relates to an ozone sensor used for ozone concentration control and ozone detection in ozone generators and ozone utilization equipment. Although ozone is used in many fields such as water and sewage water treatment for purposes such as sterilization, medicine, and the food industry, even the smallest amount of ozone is harmful to the human body. Under these circumstances, although redox titration, spectrophotometry, ultraviolet absorption spectroscopy, etc. are commonly used to measure and detect ozone concentration,
Although a sensor element using In2O5 has been proposed as a simpler method for measuring ozone concentration, the problem to be solved by the invention is, however, that the ozone measuring devices that have been used in the past are generally manual, require complicated operations, and are expensive. Although it has the disadvantage that it cannot be easily used because it is
1 is heat.The present invention solves the above problems and provides an ozone sensor made of a practical material that is chemically unstable and has problems with long-term stability. Objectives and Means for Solving the Problems In order to achieve the above objectives, the ozone sensor of the present invention has the following features:
A pair of electrodes is provided on the substrate, and C□ is placed between the pair of electrodes.
The ozone sensor according to the present invention has a structure in which a film-like gas sensitive material mainly composed of Co50= is used as the gas sensitive material. In addition, a small and lightweight ozone sensor can be easily manufactured.Embodiments Hereinafter, embodiments of the present invention will be explained with reference to the accompanying drawings. 1 is a top view of an embodiment of the ozone sensor according to the present invention, and FIG. 2 is a sectional view taken along the line A-A' in FIG. 1. In FIGS. 1 and 2, 1 is an alumina substrate (3 x 8 x O, 5 mm) 2 is a film-like gas sensitive material mainly composed of Co50a 3 is a pair of platinum electrodes (width 1 mm) formed on the substrate 1 in advance Example 1 1 CO on the substrate 1 on which a pair of platinum electrodes 3 are formed
The film was formed by screen printing, which is one of the wet film forming methods, using an ink prepared mainly from
Example 2 An ozone sensor was prepared in which a film-like gas sensitive body 2 (3 x 4 mm, thickness 2000) made of Co3O4 was baked at 500°C. Co
Produced by a coating method, which is one of the wet film forming methods, using a coating solution containing nitrate as a starting material.
A film-like gas sensitive body 2 (3x4mm,
Comparative Example 1 in which an ozone sensor with a thickness of 2,000 mm) was fabricated.A substrate on which a pair of platinum electrodes 3 was formed in advance] was coated with an ozone sensor having the same composition as in the example by RF magnetron sputtering, which is one of the dry film forming methods. Comparative example 2 in which an ozone sensor equipped with a film-like gas sensitive body was not produced. An example and a comparative example in which a 2X4X1 mm sintered ozone sensor was produced by sintering the Comaro 04 powder prepared in advance. The shape and dimensions of the substrate and electrodes in 1 were all the same.The measurement method used to measure the ozone response characteristics of these ozone sensors was as follows: A quartz glass measuring tube with the ozone sensor fixed thereon was set in an electric furnace, and the temperature was set at a predetermined value. The change in electrical resistance of the ozone sensor was measured when air and air containing 3 ppm ozone were alternately brought into contact with the ozone sensor.The electrical resistance of the ozone sensor 20 seconds after contact with air containing ozone was measured. The results are shown in Figure 3, where Reta is the electrical resistance of the ozone sensor in the air and R is the sensor sensitivity. These results show that ozone sensors equipped with a film-like gas sensitive material produced by wet film forming methods such as screen printing and coating methods have excellent gas sensitivity to ozone.Produced by RF magnetron sputtering method It has been found that ozone sensors equipped with a film-like gas-sensitive material do not have sufficient sensitivity. Film-like gas-sensitive materials produced by screen printing or coating methods have pores with a diameter of several hundred to several thousand. The surface area of the gas sensitive material is large, and gas diffusion and reactions occur quickly even at low temperatures. Although it is considered that the response characteristics are inferior due to the almost dense film, it is practical that ozone sensors made by screen printing or coating methods show higher sensitivity at lower temperatures than ozone sensors made by RF magnetron sputtering. advantageous mu people
It was found that the ozone sensor made by the sintering method hardly responds to ozone. This is because the highly reactive ozone reacts quickly on the surface of the sintered body.
Although it was thought that sensitivity could not be obtained because the change did not reach the inside of the sintered body, the response was measured using the ozone sensor of Example 1. 1000 people, 2000 people, 5000 people, 8000 people
Assuming five types of people, the relationship between film thickness and response time was calculated, and the μ response time was 9 when brought into contact with air containing 3 ppm ozone.
The temperature of the ozone sensor was 250℃ and the 0% response time (to・) was taken. The results are shown in Figure 4. From these results, it was found that the response could be greatly improved by reducing the thickness of the gas sensitive body. Example 3: An ozone sensor was fabricated by adding 0.1 wt% of Pd to a film-like gas sensitive body (1000 and 5000 mm thick) made of Coco4 formed by a screen printing method. Measure the responsiveness at 250℃ using the same method as
The results are shown in FIG.

As a result, it was revealed that the response was improved by adding Pd. This is thought to be because Pd acts as a catalyst and promotes the surface reaction. Next, Examples 1, 2, and 1 C.

A film-like gas sensitive material made of Ine○3 instead of 304 (
The change in sensitivity over time was measured for an ozone sensor (Comparative Example 3) with a film thickness of 2,000 ℃. Measure the electrical resistance change at 250°C using the same method as above.a Sensor sensitivity (RI
IntQ
26. s is an n-type semiconductor, and its electrical resistance increases due to ozone. Sensitivity is Rat・/R instead of R mouth/Rap@
This result obtained by , is shown in Figure 6. This result I
The ozone sensor equipped with a film-like gas sensitive material made of ntos has a tendency for the sensitivity to gradually decrease. As has been clarified in the nine or more Examples, the ozone sensor according to the present invention has extremely excellent characteristics. (It is also possible to use methods such as offset printing, other printing methods, and spin code methods.) In either case, it is possible to produce an active gas sensitive material with a high surface area. The starting materials for the gas sensitive material are not limited to the examples, but include acetylacenate and acetate.
It is possible to appropriately select and use materials suitable for the chlorination method and other film forming methods.Furthermore, it is also possible to use metals or metal oxides other than Pd as additives. Alternatively, 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. Effects of the Invention The ozone sensor 1 according to the present invention has excellent gas detection characteristics and excellent thermal stability. It is small, lightweight, and inexpensive, and is suitable for ozone concentration control and ozone detection in ozone generators and ozone utilization equipment.

[Brief explanation of the drawing]

Fig. 1 is a top plate of an embodiment of an ozone sensor according to the present invention. Fig. 2 is a cross-sectional view of the same. Fig. 3 is a diagram showing the temperature characteristics of sensor sensitivity. Fig. 4 is a diagram showing sensor responsiveness. is P
Fig. 6 shows the effect of d addition on the responsiveness of the sensor. Figure 6 is a diagram showing the change in sensor sensitivity over time. Muto...Substrate 2. Gas sensitive body 3. Den Kaede's name and patent attorney Osamu Koka Diarrhea diagram of the second person in the Ming Dynasty! - 1 alumina differential plate) 2---Gas type pre-assembled body 3-1 white 4 electrodes (electrodes) Fig. st /jj Fig. Back X (in) Fig. R2 taken (A)

Claims (3)

[Claims] (1) An ozone sensor characterized in that a pair of electrodes is provided on a substrate, and a film-like gas sensitive material mainly composed of cobalt oxide (Co_3O_4) is provided between the pair of electrodes. (2) The ozone sensor according to claim 1, wherein the film-like gas sensitive body is formed by a wet film forming method. (3) The ozone sensor according to claim 2, wherein an organic metal compound or an inorganic metal salt of cobalt (Co) is used as a starting material.