JPS5975601A - Method of producing porous 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 humidity-sensitive resistor used in the construction of a humidity-sensitive element, particularly a Ti
The present invention relates to a method of manufacturing a porous textured moisture resistor using an O2-8nO2 ceramic porous body.

As humidity-sensitive resistors that utilize the property that electrical resistance changes depending on humidity, F'e 2Q8 and p'e
sQ4.

TielI, ZnO, ZnO-Cr108-VBOII
-Ll 110+Tio! -V2O3゜MgCr204
-TiO2, A720B thin films, AtP(M, etc.) are known.Although these metal oxides have chemically and thermally stable properties, most of them have relatively high specific resistance; In addition to having hysteresis characteristics,
Most of them require heating cleaning because their moisture absorption properties deteriorate over time due to repeated absorption and desorption of moisture.

In addition, the applicant had previously proposed (%Application No. 56-66638
Reference) Although the TiO2-8nOz humidity-sensitive resistor ceramic composition containing TalI05 etc. does not require heating cleaning under specific usage conditions and has extremely good properties compared to the metal oxides etc. mentioned above. However, the disadvantages are that the resistance value at a relative humidity of 20% is relatively high, several tens of MΩ, and that some changes over time are observed in harsh atmospheres such as tobacco. In addition, other non-heating type moisture sensitive resistors that do not require heating cleaning have been proposed, for example, Japanese Patent Application Laid-Open No. 52-26293.56-420.
1.57-36813, etc., or [as described in Nikkei Electronics J July 6, 1981 issue, p. ), and the resistance value quality ratio is about 1.7 to 20 digits.

Therefore, an object of the present invention is to provide a method for manufacturing a porous textured moisture resistor that can easily produce a non-heated porous textured temperature resistor that exhibits extremely stable humidity-resistance characteristics over a wide humidity range. There is a particular thing.

In order to achieve such an objective, the present invention provides
25 pieces are impregnated and heat treated.

Specifically, first, 5nOx (1<x≦2)1-99m
o1% and T'10x (1<x≦2) 99-1.
The main component is Ta2O3,5b20
LI, Nb2O5, woa, In2O3, phosphate,
At least one kind of lanthanum-based rare earth oxide is added, and PVA, nitrocellulose, etc. are added as a binder at 0 to 5%.
After adding and mixing in the wt% range, 0.2-5 t/c
Molding at a pressure of i and a temperature of 1000-1500℃
Sinter for ~5 hours. The open pore surface of the thus obtained porous sintered body with a pore radius distribution of 200 to 6000 A and a porosity of 35 to 55 cm is coated with at least one of an alkali metal, such as sodium, potassium or lithium, or phosphorus or sulfur. (After applying a weight of 0.1 to 25% impregnated (the amount of impregnation can be determined by ordinary elemental analysis)
, and further subjected to heat treatment at 90°C to 1200°C for 0.1 to 2 hours. Next, at least one pair of electrodes, such as PT, are attached to this sintered body.

By forming and applying Au, RuO2, etc., a non-heated porous textured moisture resistor can be formed.

By using the TiO2-8nQz ceramic material in this way, it is possible to reduce the sintering temperature for 2 hours and the molding pressure to form a porous body with the desired pore radius distribution compared to when using other ceramic materials. Restrictions on manufacturing conditions have been relaxed, allowing production of 200 to 6. A porous body having a pore radius distribution of oooX can be manufactured. This situation is shown in FIG.

In other words, Fig. 1 (a), (b), (c), and (b) show sintering temperatures of 1050°C for 2 hours, 1150°C for 2 hours, and 1150°C for 2 hours, respectively.
x2hr, 1250℃×2hr, 1350℃×2h
The pore radius distribution is shown when r is taken as r.

Furthermore, such Ti0i+-8r+02. The open pore surface of the porous material reacts with alkali metal, phosphorus, or sulfur ions, resulting in the formation of a stable moisture-sensitive material.
, this modification is shown in Figure 2. The figure (,) shows an example before modification, and the figure (b) shows an example after modification, and in both figures, the white line shown corresponds to 1 μm.

The reason for setting the above-mentioned ranges for the sintering temperature of 9 hours and the molding pressure is that by combining these conditions, the pore radius distribution of 200 to 6000A can be corrected, and the porosity can be adjusted to 35 to 55q6. It is possible to obtain a porous body.
It is.

Mapco, the amount of adhesion of alkali metals, etc. is 0.1 to 2.5wt.
Chidoshi 7 is less than 0.1wt% in Reference Example 1 described later.
As can be seen in Figure 4 (a), the moisture sensitivity is insufficient and changes over time over a long period of time. This is because the hysteresis increases when the value exceeds 25w.

The heat treatment temperature after adhering alkali metal etc. to the glass is 9oo~1
The reason for this is to form a stable moisture-sensitive substance.If the temperature is lower than 900℃, the subsequent one-pole baking will occur at a temperature of 800 to 91J (J℃). When the temperature exceeds 1,200°C, although it has moisture-sensitive characteristics (see Reference Example 2 (see Figure 4 (1)) described later), alkali metals etc. react violently with the TlO2-8n02 ceramic body, causing the body to deform. It becomes difficult to apply electrodes.

Hereinafter, the present invention will be explained in detail using Examples.

First, TiO2 and 5n02 are used as main components, and these are accurately weighed and mixed at a molar ratio of 1:1. next,
Add 3.85 w of 'pa2Q5 to this main component as an additive.
t% is added and dry mixing is performed using an agate crusher. Next, 2 wt% of polyvinyl alcohol and coal were added as a binder to this mixed powder, and the mixture was compressed at a pressure of 2 t/cm2 to form a disk shape with a diameter of 7 rtrm and a thickness of 0.5 mm, and then placed on an alumina boat. Placed in an electric furnace using a siliconite heating element at f1250℃, 2
Perform baking time. After polishing the sintered body thus formed to a thickness of 0.35 m+n, it is immersed in a 20 wt % NaOH solution for 5 minutes to impregnate it with sodium ions. Thereafter, heat treatment was performed at 900° C. for 30 minutes to obtain a moisture-sensitive resistor ceramic composition. After screen printing this disk-shaped double-sided IPT paste, 8
Electrodes were formed by baking at 80° C. for 10 minutes to form a porous textured moisture resistor. This is further added to a mounting stem to form a moisture sensing element, as shown in FIG. Figure (a) shows a front view, and figure (b) shows a plan view.

In the figure, 1 is a moisture-sensitive resistor with a PT electrode 2 attached, 3
is a mount stem made of an alumina substrate, 4 is a lead wire as a terminal for external extraction, and 5 is a PT lead wire.

When this humidity sensing element was placed in a constant temperature and humidity chamber and the resistance value between the electrodes was measured while changing the relative humidity of the atmosphere, a humidity-resistance characteristic as shown by <0 in FIG. 4 was obtained. Further, its temperature dependence is shown in FIG. In Figure 5, (a), (b)
, (c) and ni) each have a temperature of 16°30.411.
The humidity-resistance characteristics at 50°C are shown. Temperature coefficient is 0.8
SR[/'C is small. Still, FIG. 6 shows the hysteresis characteristics of this device at 30° C., and it can be seen that the device has sufficiently satisfactory characteristics. In this case, the measurement circuit is I
Using a circuit in which the element and an IOKΩ resistor were connected in series to a KHz, IV power source, the voltage across the resistor was measured, and the resistance value of the element was calculated from that value.

In addition, the frequency characteristics of this element in the range of 50 Hz to IKHz are 5 in the relative humidity range of 30 to 90, as shown in Figure 7.
Excellent, less than 1. In addition, in the same figure (a),
(0), (c), ni), and f have a frequency of 10.
Hz, 50Hz, 100Hz, 1KHz, 10KH
The characteristics in the case of z are shown. Furthermore, FIG. 8 shows the response characteristics. In the same figure, (A) shows the characteristics of the moisture absorption process from 60 degrees to 90 degrees, and (J) shows the characteristics of the dehumidification process from 90% to 60%, which are fully satisfactory at 120 seconds and 180 seconds, respectively. However, this characteristic does not take into account the time constant of the device, and it is actually much faster.

Furthermore, when it was left in an atmosphere of 40°C and 80cm for 2300 hours and the change in resistance-humidity characteristics over time was determined, the results shown in Figure 9 were obtained, indicating that it is a very stable humidity sensing element. I understand. Note that (a), '(b), (c), and ni) in the same figure have relative humidity of 20.40, 60°80, respectively.
The characteristics in case of % are shown.

The example described above is referred to as Example 1, and other examples (Examples 2 to 8) were similarly produced by changing only the alkali metal impregnation conditions and subsequent heat treatment conditions, and Reference Example 1 with a small amount of alkali metal impregnation. The results of measuring the resistance values at a relative humidity of 20 degrees and 90% for Reference Example 2 in which the heat treatment temperature was increased are recorded on the lower coat together with the results of Example 1. Moreover, the humidity-resistance characteristics are shown in FIG.

As mentioned above, (A) in the figure shows the case of Example 1, but Example 2 is also almost the same. Again (mouth) ~
(G shows the results for Examples 3 to 8, respectively, and (A) and (S) show the results for Reference Examples 1 and 2.

)1 ``In this way, even at a relative humidity of 20%, the resistance value is several MOs to several tens of ohms or less.

In addition, in the above-mentioned example, only the case where Na or K was used for surface modification of the ceramic porous body was explained, but the present invention is not limited to this, and other alkali metals, phosphorus, As mentioned above, sulfur may be used.

As explained above, according to the present invention, Ti is used as the element body.
Because O2-8n02 ceramic is used, porous elements with a pore radius distribution suitable for use as moisture-sensitive resistors can be easily produced under a wide range of manufacturing conditions, and they can be made easily, unlike most conventional elements. The pore distribution diameter is 300O
Even if it is not less than A, the ceramic porous material itself can be easily modified even if it has a considerably large pore distribution radius by modifying the surface with alkali metals, phosphorus, or sulfur to form a surface with moisture-sensitive points. It is possible to form a humidity-sensitive resistor that is sensitive to humidity, and the resistance value is not too high at low humidity13
In fact, the porous textured moisture resistor obtained by the present invention has a larger resistance change ratio with respect to relative humidity and smaller hysteresis than a conventional moisture sensitive resistor containing an alkali metal.

Furthermore, since it shows almost no change over time, it does not require a mechanism to prevent changes over time due to heating, unlike many conventional products, and thus allows continuous measurement of humidity. Of course, it goes without saying that by adding a heating device, changes over time due to adverse environments such as oil and dust can be easily eliminated, making it possible to perform more stable humidity measurements.

[Brief explanation of the drawing]

Fig. 1 is a diagram showing the dependence of the pore radius distribution of the ceramic porous body on sintering conditions, Fig. 2 (-) and (b) are diagrams showing the open pore surface of the ceramic porous body before and after modification, 3(&) and (b) are a front view and a plan view showing a humidity sensing element using a porous moisture resistor manufactured by applying the present invention, and FIG. 4 is a humidity-resistance of the humidity sensing element. Figure 5 shows the temperature dependence of humidity-resistance characteristics, Figure 6 shows the hysteresis characteristics, Figure 7 shows the frequency dependence, and Figure 8 shows the response characteristics. FIG. 9 is a diagram showing changes over time. 1... Moisture sensitive resistor, 2... Electrode. Patent Applicant: Tokyo Cathode Laboratory Co., Ltd. Agent: Kazuki Yamakawa (1 person) Fig. 1 IIB%Lia jx+00f) Fig. 2 (α) t-'o> TO sentence f chant 6 (01) Figure 6: 1 bow history 1゛shi!・No [(01o) Figure 7 Rito Dodo (@/,”)

Claims (1)

[Claims] At least one of an alkali metal, phosphorus, or sulfur is added to the open pore surface of a TiO2-8nQ2 ceramic porous body having a pore radius distribution of 200 to 100 A and a porosity of 35 to 55 cm. After impregnation, 9
A method for producing a porous textured moisture resistor, which comprises performing heat treatment at 00 to 1200°C for 0.1 to 2 hours, and forming at least one pair of electrodes on the surface of the obtained porous body.