JPS5891601A - Moisture sensitive resistor - 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 relates to a moisture sensitive resistor.

The humidity-sensitive resistor is made of a material whose electrical resistance changes depending on the humidity, and the humidity can be determined by determining the electrical resistance. It is physically, chemically and thermally stable;
In addition, it is desired that the electrical resistance changes largely in response to changes in humidity.

Conventionally, Kanaoka fused compounds such as iron oxide and chromium oxide have been used for moisture-sensitive resistors.

However, since these metal oxides have high electrical resistance, it is difficult to electrically detect electrical resistance with high accuracy. Furthermore, since metal fluoride is not a sintered body, it has the disadvantage that it is prone to errors due to coatings and has poor sensitivity.

A moisture-sensitive resistor that eliminates this drawback uses CR, O, and Zn.
O line KLI, 01Ha, OlK, 0, Rb, OlOu
, 0 has been proposed. However, although this sintered body has physical and chemical stability, has low electrical resistance, and is less affected by surface coatings, it is necessary to sinter at high temperatures (1100 to 1800 ℃).
℃) is required. Along with this, monovalent metal oxides such as O1N~0, L1, 0, Ou, O, etc. are difficult to manufacture because they easily evaporate at low temperatures.

The present inventors conducted research to provide a moisture-sensitive resistor that is physically and chemically stable, has electrical resistance that changes significantly in response to changes in humidity, and can be sintered at a relatively low temperature. A moisture-sensitive resistor whose main component is a fired product of a mixed composition of Ll, 0, and ZnO in a specific ratio can be fired at low humidity and has excellent moisture-sensitive characteristics. 82.4 months 86.5~8 years. This is a moisture-sensitive resistor made of a sintered body that absorbs moisture.

Li, 0 to ZnO tono full aggregate ki, Li, 0.
In addition, Li, 00.00, which generates Li,0. ,
LiOH.

A lithium compound such as L I HOOs and zinc white or a zinc compound that thermally decomposes to produce ZnO are mixed so that the Li, O components and ZnQ component have a predetermined molar ratio,
The obtained mixed composition is calcined at about 850°C to perform decarboxylation or thermal decomposition, the obtained calcined product is crushed, and then the crushed calcined product is molded into a desired shape under pressure. It is obtained by firing at about 750°C.

If the above-mentioned decarboxylation and calcination steps are performed under reduced pressure of less than IQ"sawH1i4, preferably about 1Q"mHp,
This is preferable because each step can be completed quickly. The pressure of the molding force G is 1,000 to 500 kg/cm *
is the standard.

When the molar ratio of Ll,0 and ZnO becomes less than % (the range of change in resistance value with respect to humidity becomes small, it becomes unsuitable for practical use. When the molar ratio of Ll,0 and ZnO becomes 3 or more, L
ItO evaporates violently, resulting in poor sinterability and high electrical resistance, making it unsuitable for practical use.

Since the moisture-sensitive resistor of the present invention is constructed as described above, its surface condition will not change even if it is left in the atmosphere for a long time.
Humidity can be measured even under high humidity for long periods of time.

Since the humidity sensitive resistor of the present invention has a small electrical resistance, relative humidity
The accuracy is good because the electrical resistance changes greatly over the entire range from 100% to 100%.

In addition, since the moisture-sensitive resistor of the present invention is sintered at low temperature, the working environment during manufacturing is favorable (Li, 0 minute sublimation and evaporation loss are extremely small.

The resistance characteristics of the moisture-sensitive resistor of the present invention change very little even after a long period of time. Also, responsive electric relative humidity θ~1
At 00%, the response speed is extremely fast, within 20 seconds.

The humidity-sensitive resistor of the present invention is stable up to 500° C. as determined by differential thermal analysis and thermal device measurement.

The humidity-sensitive resistor of the present invention has the above features and is used as a sensor for humidity measurement and humidity control.

Next, the relationship between electrical resistance and relative humidity (%) of the manufacturing examples of humidity-sensitive resistors according to a few embodiments of the present invention and their compositions was determined, and the results are shown in FIG.

Production example Reagent grade lithium carbonate (purity 9999%) and reagent grade zinc oxide in a molar ratio of 1:1O11:8, 1:1
．． The mixtures were mixed in ratios of 2:1, 3:1, and 4=1, and the respective mixtures were wet-pulverized and mixed in a bot mill containing an agate ball. After drying each of the obtained mixtures, decarboxylation was performed by calcining in a platinum crucible under reduced pressure at 850°C for 6 hours in a normal electric furnace.
It was molded into a plate-shaped molded product with dimensions of 5w x 15g under a pressure of kt/C1n'. Each of the obtained molded bodies was placed in a platinum crucible, and these crucibles were then placed in an ordinary electric furnace and fired at 750°C for 8 hours, and after firing, the crucibles were allowed to cool naturally. The obtained fired body was used as a moisture-sensitive resistor.

For characteristic testing, moisture-sensitive resistors with a distance of 5IIIl between electrodes were prepared.

The relative humidity of the atmosphere between the electrodes was set in the range of 0 to 100%, the electrical resistance between the electrodes corresponding to the humidity was determined, and the relationship between humidity and electrical resistance characteristics for each humidity-sensitive resistor was determined. is shown in Figure 2.

Note that this measurement 1 was conducted at 20°C.

As is clear from Figure 2, humidity-sensitive resistors with a molar ratio of Li to ZnO of 0.5 or less have a small change in electrical resistance with respect to changes in relative humidity, and when the molar ratio is 8 or more, the electrical resistance is small. It becomes large and becomes unsuitable for practical use.

On the other hand, when the molar ratio of Ll,0 and ZnO is 0.5 to B, the electrical resistance is small, and the change in electrical resistance corresponding to the change in relative humidity is the same as the relative humidity in the entire range of relative humidity 0 to 100%. It was observed that the relationship with the resistance value was almost linear and changed significantly.

[Brief explanation of the drawing]

Figure 1 is an explanatory diagram of measurement of a humidity-sensitive resistor, and Figure 2 is a diagram showing the relative humidity of molded bodies fired with various molar ratios of Ll,0 and ZnO.
〇Patent showing the electrical resistance curve Applicant Nippon Cement Co., Ltd. Representative Patent Attorney Tsukasa Minato No 1 Figure 1 Figure 2 Sum of degrees N9L (7)

Claims (1)

[Claims] A moisture-sensitive resistor comprising a sintered body having a composition of Ll,0 and ZnO in a no molar ratio of 0.5 to 8:1.