JPS5898901A - Moisture sensitive 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 relates to a humidity sensing element that detects humidity as an electrical signal by utilizing the property that its electrical resistance changes depending on humidity.

Conventionally used moisture-sensitive resistors include salts such as lithium chloride and chloride/L/sium.

In addition, since metal oxide powder has extremely high moisture adhesion resistance and quick drying properties, Q r 203 * Fe!
There is a method in which a thin film is made of fine powder such as Os +N 1303, Zoo, Mul, 01, etc., and the electrical resistance of the film is measured. Furthermore, in order to lower the resistivity, there are also sintered moisture sensing elements to which alkali metal oxides (Li!0.20) are added, and polymer type elements that utilize the hygroscopicity and swelling properties of organic materials.

However, elements such as lithium chloride are susceptible to dirt, easily elute when saturated with water, and are unstable, and have a narrow detection range. Types that use fine metal oxide powder generally have a high specific resistance, so this! It is difficult to detect electrically with high precision. Furthermore, elements to which alkali metals and the like are added have a significantly large humidity cycle history and a large change over time. Furthermore, polymer type elements have the disadvantage that their use environment conditions are limited because their characteristics change significantly at high temperatures.

The device of the present invention is a sintered moisture sensing device made of ZnFe2O4, and is intended to provide the following effects. That is, the specific resistance value of the metal oxide is lowered to a value that can be easily detected electrically, and the amount of change in electrical resistance with respect to humidity changes is large, and the detectable humidity range is widened.

First, since the element of the present invention is a high-temperature sintered body, it is stable even at high temperatures1, and exhibits characteristics that change little over time.

FIG. 1 shows the shape of the moisture sensitive element of the present invention, where l is Zn.
It is a sintered body made of Fe2O4. Reference numeral 8 denotes a thin rolled electrode, which is attached to both sides of the sintered body 1 by means of printing, vapor deposition, or the like. This electrode material is Mug, Muu
, ILtxO1, etc. are used.

3 is a pair of lead wires for extracting electrical signals.

It is firmly attached to the electric wire w2 by soldering or conductive paste.

Next, an example of a method for manufacturing a moisture-sensitive element having the above structure will be described. ZnO and Fe2O were blended as starting materials so that the composition ratio was equal to 7μ. After wet mixing these raw materials, polyvinyl altu~ (binder) was added and blended, and the mixture was directly pressure-molded at a pressure of 1 tOn/d into a disc shape with a thickness of 15mm, and then heated to a temperature of 1050°C. and baked for 2 hours. This fired element was further cut to a thickness of 0.5 mm. Next, as shown in FIG. 1, the sintered body I K Ru OH electrode 2 is printed and baked, and the lead wire 8 is attached to this electrode by soldering or using a conductive paste. The moisture sensitivity characteristics of the device of the present invention thus obtained are shown in FIG.

In Fig. 2, the resistance value of the device of the present invention increases greatly from about 107 to 10'Ω from the low temperature side to the high humidity side.
Moreover, since it exhibits a practically appropriate resistance value, it can be used as a moisture-sensitive element.

The present invention is not limited to the above-described embodiments, but can be modified in various ways as described below.

(1) In this example, Fe2O and ZnO were used as starting materials, but for example, F.304.
Fed, iron nitrate, etc., ZnC50, zinc chloride, zinc bromide, etc. may be used as zinc raw materials. (2) In this example, IE electrodes are attached to both sides of the element, but two electrodes are attached to one side. It may also be attached in a comb-like shape.

Alternatively, a sintered body formed by directly integrating lead wires may be used.

As mentioned above, the element of the present invention is made of ZnFe2O4, and its resistance value is highly dependent on humidity, and covers a wide range from low humidity to high humidity.

There is resistance change and little hysteresis. Moreover.

Since it is a sintered body, it can be used over a wide range of temperature ranges and can be used as a new element with little change over time.

[Brief explanation of drawings]

FIG. 1 is a perspective view showing an embodiment of the present invention, and FIG. 2 is a diagram of moisture sensitivity characteristics of a ZnFe2O4 element, which is used to explain the present invention. l... Sintered body, 2... Electrode, 8... Lead wire. Representative Patent Attorney Takashi Okabe @2 Diagram

Claims (1)

[Claims] A moisture sensing element made of a sintered body of ZnFe2O4.