JPS60160102A - moisture sensitive resistance element - Google Patents

Abstract

(57) [Summary] This bulletin contains application data before electronic filing, so abstract data is not recorded.

Description

Detailed Description of the Invention The present invention is made of a sintered body of metal oxide, and can detect changes in relative humidity as changes in electrical resistance, and is less susceptible to deterioration of detection ability due to miscellaneous gases in the air. The present invention relates to a moisture-sensitive resistance element.

in general,! The sensing part of the I & moisture resistance resistance element is made of organic polymers such as polyamide resin, or ethylene.

Metal oxides such as F sm Os and Crl ol are used. However, metal oxides than organic polymers.

It is chemically and physically relatively stable and is promising as a material for moisture-sensitive resistance elements. However, 0 normal metal oxides are
It has drawbacks such as high specific resistance, small resistance change due to humidity change, and hysteresis in humidity-resistance characteristics under humidification-dehumidification condition T, so it is not suitable as a material for humidity-sensitive resistance elements as it is. It wasn't. Therefore, + M l-! is a material for a moisture-sensitive resistance element that has a zero-shot resistance, whose value changes by an order of magnitude from B to B, and whose characteristics do not change over a long period of time even in a high temperature and high humidity atmosphere T. A xFe
toa-a system (where 1M/: magnesium (Mg) or zinc (Zn), A: alkali metal, i.e. lithium (Li), sodium (Na), or potassium potassium)
.

Find a sintered material (Fe: iron) and use this material to
We have manufactured an excellent moisture-sensitive resistance element and have already applied for it (patent application filed in 1983).
6-1965114). This element has the feature that characteristic fluctuations are extremely small even if it is used for more than one year in a relatively clean room.

However, when exposed to static electricity contaminated with gases other than moisture, such as cigarette smoke, the electrical resistance 1 of the element increases, causing discrepancies with the initial characteristics.

This discrepancy in characteristics disappears when the device is heated to a temperature of about 400° C. or higher for several minutes. However, it does not require frequent heat treatment during use.

It was necessary to incorporate a heating heater and a control circuit into the element, which caused problems such as the structure of the element itself becoming complicated. Therefore, the inventors developed the above-mentioned M1-, A! Based on the discovery that when a low melting point metal oxide is added to an F, O, a-based substance, this substance becomes inert to miscellaneous gases other than moisture, such as cigarette smoke, and the above-mentioned conventional problems were solved. We have completed a moisture-sensitive resistance element that overcomes this problem. Namely.

The present invention includes + MI-x AxFszOa-a (however, 0
M is magnesium (Mg) or zinc (Zn), A is an alkali metal, α001 (x (0, 2, a is the number of oxygen vacancies +
A composite oxide represented by Fe (iron) and O (oxygen).

Boron oxide (neon), bismuth oxide (BitOn)
.

Vanadium oxide (VtOa) and lead oxide (PbO
) A moisture-sensitive resistance element comprising at least one low melting point oxide selected from the following.

The humidity-sensitive resistance element according to the present invention exhibits a large change in electrical resistance with respect to changes in relative humidity, and in addition to a small amount of hysteresis in the characteristics, it also has a small amount of low melting point oxide. It has an excellent property of being less susceptible to characteristic deterioration due to miscellaneous gases such as cigarette smoke.

The present invention will now be described in more detail.

The moisture sensitive resistance element according to the present invention is made of a composite oxide and a low melting point oxide. The above composite oxide is spinel r MF at 04 J M O, 1-201
-r M
It is represented by the general formula l-X A fem0a-a J.

Here, the value of X is in the range α001 to α8,
Within this range, good moisture sensitivity characteristics are exhibited.

Furthermore, in the range of αO1 to α06, the relationship between the relative humidity and the logarithm of the electrical resistance value becomes approximately linearly proportional, resulting in a humidity-sensitive resistance element that is easier to use.

Further, a is a numerical value determined from the amount of alkali metal,
Its value is approximately x/g.

On the other hand, the above-mentioned low melting point oxides are -Bx Ox, Vt Oa
.

One type or a mixture of two or more of BitOn and PbO in an arbitrary ratio may be used. This low melting point oxide has the role of making the humidity resistance element inert to gases other than moisture. The content of the low melting point oxide in the moisture sensitive resistance element is desirably α5 to 2 mol%. When the amount exceeds g mol %, the activity against not only miscellaneous gases but also moisture becomes low, and the humidity sensitivity of the humidity-sensitive resistance element becomes low. On the contrary, α6
At mol%, the electrical resistance value also changes with respect to miscellaneous gases, and the effect of adding the low melting point oxide becomes apparent (
It becomes.

The low melting point oxide is present so as to cover the composite oxide. Therefore, the electrical resistance value of a humid resistance element changes depending on the relative humidity of the surrounding atmosphere, and it also contains a low melting point oxide.

It has excellent performance in suppressing sensitivity reduction due to miscellaneous gases other than moisture.

That is, unlike the conventional method, cleaning by heating or the like, which is performed every time the sensor is used, is no longer necessary, so there is no need for a cleaning heater and a control circuit.

The moisture-sensitive resistance element according to the present invention can be manufactured, for example, as follows. First, in order to obtain a composite oxide, a desired amount of gold boron oxide, hydroxide, metal subacid, nitrate, etc., which becomes an oxide by heating, is used as a raw material.

Weigh and mix, and if necessary, grind with a ball mill or the like. The obtained mixed powder was calcined at 80ON at 1000°C,
A composite oxide with a spinel structure as its main component.

On the other hand, a powder of a low melting point oxide is prepared, mixed with the above composite oxide, and pulverized to obtain a raw material for the powder. The particle size of the powder is α1~
A range of 111 m is desirable from the viewpoint of sensitivity, durability, etc. of the moisture-sensitive resistance element. the mixed powder.

If necessary, add a binder such as polyviny-A//alcohol and knead to produce 80 kq/d-2 ton/d.
f) Apply pressure to the desired shape of one disc-shaped part to form a molded body. Furthermore, the molded body is heated to 6bO6~
A moisture-sensitive resistive element according to the present invention is obtained by firing 1- for a time at 1100°C. The firing temperature is a temperature above the melting point and below the boiling point of the mixed low melting point oxide. As described above, the humidity-sensitive resistance element according to the present invention can be manufactured.

#, W & oxide on the surface of the moisture resistance element! = Um electrode.

Furthermore, after forming a silver film thereon, lead wires may be soldered.

Hereinafter, the present invention will be explained in detail.

First, each implementation number 1 to 16 in Table 9. and C1 as a comparative example
, C2.

MgCO5-N Hatake, CO,, KNO□-LizCOs,
A raw material for a composite oxide is obtained by combining appropriate FsOl. After mixing and crushing these raw materials in a mortar.

The material was roughly formed into a disk having an r1F diameter of 11 at a pressure of about bah/d, and heated in the air at a temperature of 800 to 1100 DEG C. for 2 hours to obtain 18 types of pre-fired products. Each calcined body was again crushed into powder using a mortar and pestle, and the low melting point oxide shown in each execution number was added to each powder in powder form, and the mixture was remixed and crushed. Next, f) Powder power 1 ton/d
Tem! 11 W, I! It was molded into a soft circular disk and fired for 9 hours at the firing conductivity shown in Table 8. As described above, the 16 types of moisture-sensitive resistance elements according to the present invention,
A 2W1 moisture-sensitive resistance element was manufactured for comparison.

After that, both sides of the moisture-sensitive resistance element were polished, washed with acetone, and ruthenium oxide (Rus) was applied to both sides of the m-element.
t) The paste was applied in a circular shape with a diameter of 10 m, and heated to 800 ti in an electric atmosphere to bake the electrode. moreover,
By applying silver paste to a part of the surface of this electrode and heating it to 700°C.

A silver surface was formed, and a semicircular lead wire was attached thereto.

In order to investigate the humidity-sensitive characteristics of the above-mentioned humidity-sensitive resistance element.

First, these elements were placed in a temperature and humidity chamber, and the relative humidity was varied within the range of 0 to 100% while keeping the temperature inside the chamber constant at 26.degree. The relationship between the above relative humidity and the electrical resistance of the element was determined. The 11HK resistance of the device was measured by an AC bridge (at frequency 1KH). A nearly linear relationship can be seen between the logarithm of electrical resistance and relative humidity. A typical example of these relationships is shown in diagram m1. The numbers on the curves correspond to the elements with implementation numbers shown in the table.

Next, in order to examine the degree of deterioration of the moisture sensitivity characteristics of the above element due to cigarette smoke, one rolled cigarette was placed in a container with an internal volume of g50 aa and burned, and the above element was further placed in the container for 24 hours.
I left it for a while. After this test, the relationship between relative humidity and electrical resistance was determined. the above.

The moisture sensitivity characteristics after repeating the test 8 times are as follows:
In the case of No. 16, only a deviation of 10 or more was observed from the initial characteristics, but in the CI and C2 comparative examples, deviations of 20% or more were exhibited. Figure 2 shows 'gi! Number 8 and C
For case I, the initial characteristics (solid line) are compared with the characteristics after conducting the smoke test three times (dashed line).

In Figure 8,! J! Regarding the case of test number 8 and CI, the change in characteristics depending on the number of tobacco tests was examined at relative humidity of 90
%, 60 type, and resistance value measured at 80%. As can be seen from these figures, the resistance value of the moisture-sensitive resistance element according to the present invention shows very little change regardless of the number of tobacco tests, but in the comparative example, the resistance value increases as the number of tests increases. To increase. That is, it can be seen that when the element of the comparative example is exposed to smoke, the moisture sensitivity characteristic becomes low, but the moisture sensitivity characteristic of the element according to the present invention hardly changes. In addition, by adding a low melting point oxide, a low 1. & Since the electrical resistance value in the atmosphere is slightly lowered, the 1g humidity sensitivity is slightly lowered, resulting in improved mechanical strength and ease of handling.

[Brief explanation of drawings]

Figures 1 to 8 are diagrams showing examples; Figure 1 is a diagram showing a typical example of the relative humidity-electrical resistance characteristics of a humidity-sensitive resistance element; Figure 2 is a diagram showing the relative humidity before and after the smoke test; @Figure showing a typical example of electrical resistance characteristics. FIG. 8 is a diagram showing a typical example of the relationship between the number of tobacco tests and the electrical resistance value. Patent Dekojin Co., Ltd. Toyota Central Research Institute (2 others)

Claims (2)

[Claims] (1) M I-x A x FexOa-a (However, 0M is magnesium or zinc, 1 person is alkali metal, α0
01 (x<O, Q, a is the number of oxygen vacancies); and a low melting point oxide selected from at least one of boron oxide, bemuth oxide, vanadium oxide, and lead oxide. A moisture-sensitive resistance element characterized by: (2) The moisture-sensitive resistance element according to claim (1), wherein the low melting point oxide is contained in an amount of 0.5 to 2 mol %.