JPS62216963A - Humidity sensor - 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] [Industrial Application Field] The present invention is directed to a composition that exhibits ferroelectricity (Pb, La).
(Zr, Ti) This relates to a moisture sensitive body made of an Os sintered body and whose capacitance value changes according to changes in humidity.

[Conventional technology]

Conventionally, A'zOs and ZrSiOs have been used as moisture-sensitive materials whose electrical resistance changes in response to the humidity in the atmosphere.
, MgA 120a , MgCr20s , CrzO
Porous bodies of metal oxides such as a, Fez Os, and T'i 01, electrolyte salts such as LiCl saturated solution, and organic substances such as cellulose and copolymer of hydrophobic and hydrophilic polymers are available. .

In addition, organic polymer + FET type, thin film A 120, and Ta
, o, -MnO type moisture sensitive elements have been developed.

[Problem that the invention seeks to solve]

However, metal oxides whose resistance value changes in response to humidity have the advantage of being excellent in thermal and chemical stability and making it easy to obtain porous sintered bodies. The coefficient of temperature vs. humidity in the electrical resistance value change characteristic with respect to humidity change changes over the entire temperature-humidity region, which has the disadvantage that the temperature correction circuit becomes complicated and accuracy deteriorates.

On the other hand, temperature sensitive materials whose capacitance value changes depending on humidity generally have the advantage that the coefficient of temperature vs. humidity does not depend on temperature or humidity, but the mainstream of organic material humidity sensitive materials Lack of stability in terms of changes, operating temperature, etc. Furthermore, a moisture sensitive body made of an inorganic material requires considerable ingenuity in manufacturing due to the complexity of its structure and shape.

As described above, each of the conventional materials has some drawbacks.

The present invention is intended to solve the above-mentioned problems; the preparation of the humidity sensing body and the structure of the humidity sensing element are simple, the detected anger level is high, and
The purpose is to provide a stable moisture sensitive body with excellent temperature characteristics and little change over time.

[Means for solving problems]

For this purpose, the present invention has a basic composition of (Pbl-x Lax) (Zr, Tt+-y
) l-X/40z.

The present invention is characterized by a moisture sensitive body whose main component is a sintered body of a ferroelectric metal oxide where 0<X0.25.0<y<1.

[Effect]

In the present invention, the basic composition is (Pbl-x Lag) (ZryTi+-y)
+-wya Os, 0< x <0.25 , O<,
The calcined products and calcined crystals containing ferroelectric metal oxides of , 200~
A sandwich type heat-treated at 800°C with counter electrodes on both sides, a surface type with a temperature sensing element on a comb-shaped electrode, or a temperature sensing element packed in a container with a pair of electrodes and one side covered with a moisture permeable membrane. It is formed into an electrode insertion type that is wrapped with. The temperature-humidity coefficient of this moisture-sensitive body is constant over the entire temperature-humidity region,
Moreover, the change over time is small and stable. In addition, hysteresis and responsiveness during rapid moisture absorption and dehumidification are comparable to commercially available products.

〔Example〕

Examples will be described below with reference to the drawings.

After blending lead oxide, lanthanum oxide, zirconium oxide, and titanium oxide in the proportions shown in Table 1, a raw material for a calcined moisture sensitive element is obtained by pulverizing, kneading, drying, and calcining using a vibrating mill.

The calcined product is further compression molded at 1000kr/- to form Ol, P
Normal pressure sintering is performed at 1150° C. for 20 to 40 hours in a bO atmosphere. The fired product is pulverized using a pulverizer, and the dried product is used as a raw material for the moisture sensitive body.

Table 1 x=9. )'-65.1 y = 35 moisture sensitive material raw material was compressed by a compressor at a pressure of 200 kg/cnl to a thickness of 0.5 m.
A molded body with a diameter of 20 m and a diameter of 20 mm is made. This was cut into 3 x 3 fl under the conditions shown in Table 2: 200°C, 400°C, 600°C, s
The sample was heat-treated at oo°C for 2 hours each to obtain a humidity sensitive body.

Figure 1 of Table 2 is a perspective view of a humidity sensing element constructed by attaching electrodes and lead wires to such a humidity sensing element, where (A) is the sandwich type 1 and (B) is the surface type. , the same figure (C) is a diagram showing an electrode insertion type moisture sensing element.
In the moisture sensing element shown in FIG. 1(A), Au is vapor-deposited on the surface of a moisture sensing element l processed into a plate shape to form an electrode, to which a lead wire 3 is attached. The Au electrode 2 has moisture permeability, and the moisture sensitive body 1 absorbs moisture through the electrode 2, and the lead wire 3
Humidity can be measured by measuring the capacitance between the electrodes.

In the humidity sensing element shown in FIG. 1(B), a comb-shaped electrode 2 is formed on an insulating substrate 4, and a humidity sensing element 1 is formed thereon. Humidity sensing body 1
directly contacts the atmosphere and absorbs moisture, and the humidity can be measured by measuring the capacitance between the electrodes through the lead 'H3, as in the case of Figure (A).

In the moisture-sensitive element shown in FIG. 1(C), a moisture-sensitive element 1 is filled in an insulating box-shaped container 5 in which a pole 2 is provided, and one side of the container 5 is wrapped with a moisture-permeable membrane 6. There is. The moisture sensitive element 1 absorbs moisture through the moisture permeable membrane 6, and the humidity can be measured by measuring the capacitance between the electrodes through the lead wire 3, as in the case of FIG.

Figure 2 shows the atmospheric temperature of the moisture-sensitive element created in this way at 30°C.
, shows the relationship between relative humidity 0~90% and capacitance value at a measurement frequency of IKHz.

This figure shows that the characteristics of sample No. 1 are that the capacitance value changes greatly depending on the humidity from 0 to 90% RH, and the detection sensitivity is high.

Figure 3 shows the relative humidity O~95% versus each electrical capacity θ
The relationship between the logarithm of the difference and the capacitance in % is shown.

Each sample shows good linearity in the range of 30 to 95%.

Figure 4 shows the relationship between the measured ambient temperature and capacitance value at each relative humidity of 20 to 90% for sample No. 1, and Figure 5 shows the relationship between the measured ambient temperature and the capacitance value for sample No. 1 at each measured ambient temperature of 30 to 45°C. The relationship between humidity and capacitance value is shown.

From Figures 4 and 5, it is recognized that the slope of the obtained straight line does not change depending on temperature or humidity, and the coefficient of temperature versus humidity of this humidity sensor is constant over the entire temperature-humidity region. I understand. Its temperature coefficient is 6%RH/10°C.

Figure 6 shows the capacitance value between 0 and 90 at an ambient temperature of 30°C.
% change over time at each relative humidity.

The figure shows that the change over time is small and stable. In addition, the hysteresis and responsiveness of this moisture sensitive body during rapid moisture absorption and dehumidification are comparable to those of commercially available moisture sensitive bodies.

For samples N002 and N013, similarly to samples No. 1, the slope of the relationship between %RH and log (C-CJ is constant regardless of temperature, and the temperature coefficient is 6%RH, / 10℃. Sample No. 014 also shows good linearity in %RH vs. log (CCo) at each temperature, and although there is a tendency for the slope to become slightly larger on the low temperature side, it is sufficiently acceptable as a humidity sensor. Note that the changes over time became stable for all samples after 3 days, and almost no changes were observed after that.

[Comparative example]

The dielectric constant of the sintered body is about 600, and the basic composition (Pb+-x
Lax) (Zr, Tit-y) I-X/
403x = 0. 3'=0.65. 1-V
=0.35 and x-0°y =0.35. 1-y=
For the case of 0.65, a molded body was made in the same manner as in the example, and as shown in Table 3, heat treated at 400°C and 600°C for 2 hours each to obtain a humidity sensitive body. It was configured as shown in Figure (A).

Table 3* (Pb+-x Lax) (Zr, Tit-
y) +-++z4oz Same as the example, ambient temperature 30
Figure 7 shows the relationship between the relative humidity 0~90% and the capacitance value at a measurement frequency of 1 KHz at a measurement frequency of 1 KHz, and the relationship between the logarithm of the difference between the relative humidity and the capacitance at a relative humidity of 0%. It is shown in FIG.

The relationship shown in FIG.
Good linearity is shown in the range of 0 to 95%.

Further, the coefficient of temperature versus humidity is also approximately constant over the entire temperature-humidity region. However, as can be seen from Figure 7, the difference in capacitance between 0% and 90% relative humidity is about 150 pF.
Example sample No. 1. 3 in case of NO, 2, No, 3
The difference is small compared to 00 to 500 pF. Therefore, sensitivity becomes an issue.

From this, (Pb, LaX) (Zr,
For Ti) 0, type moisture sensitive materials, those with a high dielectric constant are suitable.

〔Effect of the invention〕

As is clear from the above explanation, according to the present invention,
It is easy to prepare the wet body and configure the humidity sensing element, and as a type of humidity sensing body that detects temperature using capacitance, it has high detection sensitivity, shows a linear relationship between humidity and capacitance, and shows a linear relationship between temperature and humidity. It is possible to obtain coefficients that are constant over the entire temperature-humidity region, thus simplifying the temperature correction circuit, etc., and improving accuracy. Furthermore, since it can be made into a stable moisture-sensitive material with little change over time, its industrial value is great.

[Brief explanation of drawings]

Fig. 1 is a perspective view of a humidity sensing element, in which (A) shows a sandwich type 1, (B) shows a surface type, and (C) shows an electrode insertion type moisture sensing element. Figure 2 is a diagram showing the relationship between relative temperature and capacitance value, Figure 3 is a diagram showing the relationship between the logarithm of the difference between the capacitance versus relative humidity and the capacitance at relative humidity 0%, and Figure 4 is a diagram showing the relationship between the relative humidity and the capacitance at 0% relative humidity. Figure 5 shows the relationship between the measured ambient temperature and the capacitance value at each relative humidity of 20 to 90% for sample No. 1. A diagram showing the relationship, Figure 6 is a diagram showing the change over time at each relative humidity of 0 to 90% of the capacitance value at an ambient temperature of 30°C, and Figure 7 is a diagram showing the relative humidity O
FIG. 8 is a diagram showing the relationship between the capacitance value and the relative humidity relative to 90%, and FIG. 1... Humidity sensitive body, 2... Electrode, 3... Lead wire, 4
... Substrate, 5... Container, 6... Moisture permeability collection application Person: Shinagawa Shirorenga Co., Ltd. Representative Patent Attorney Masanobu Hirukawa (2 people) Figure 1<A) (8,) (ri) Fig. 2 Iη# wet friend C4) Phase Zuna wet power (7-) Fig. 5 Figure 6 8 汀厘degree砿) Japanese vs. On Ii (幡) Figure 8

Claims (5)

[Claims] (1) The basic composition is (Pb_1_-_xLa_x)(Zr_yTi_1_-
_y)_1_-_x_/_4O_3, 0<x<0.25
, 0<y<1. (2) The relative dielectric constant of the sintered body of the ferroelectric metal oxide is 1
000 or more, the moisture sensitive body according to claim 1. (3) The moisture-sensitive body according to claim 1, wherein the moisture-sensitive body is processed into a plate shape, and a pair of electrodes are provided facing each other on both sides of the plate-shaped body. (4) The moisture sensitive body according to claim 1, wherein the moisture sensitive body is processed into a plate shape and is provided on a comb-shaped electrode formed on a substrate. (5) The moisture sensitive body according to claim 1, wherein the moisture sensitive body is filled in a container having a pair of electrodes, and one surface of the container is covered with a moisture permeable membrane.