JPS60251164A - Humidity sensitive material - 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] [Technical field of invention] The present invention relates to a moisture sensitive material for detecting relative humidity.

[Prior art]

Conventionally, metal oxides such as ZnO, p62'o3 and A/203, and IJ4F6204 and znCr20 have been used as moisture-sensitive materials whose electrical resistance changes with relative humidity.
Composite oxides such as No. 4 are being considered, but the measurable range of relative humidity is narrow and the W properties change over time. There were problems such as high resistance. Elements using moisture-sensitive materials such as inorganic electrolytes such as lithium chloride and devices using moisture-sensitive materials such as organic electrolytes become unusable due to electrolyte dissolution at high humidity.

There were problems such as difficulty in measuring the entire humidity range with one element. hair.

Hygrometers in which a moisture-sensitive material such as a nylon ribbon expands and contracts depending on the humidity have problems such as material deterioration and difficulty in extracting electrical signals for humidity control.

[Summary of the invention]

The present invention has been made to eliminate the drawbacks of the conventional products described above, and is made of ceramics represented by the chemical formula AMPO4 (where A is an alkali metal L1° and at least one of Na and K).

M consists of at least one of the divalent metals Mg, Ca, Sr, Ba, zn and Od. ) The purpose of the present invention is to provide a novel moisture-sensitive material that has high reliability and sensitivity and is excellent in mass production.

[Embodiments of the invention]

Ceramics according to this invention are represented by the chemical formula A M P o4 (where A is an alkali metal Li, Na
and K (both of which are composed of one type, and 2M is composed of at least one of the divalent metals Mg+Ca+Sr+''*zn and Cd) is 10 to 99, assuming that a resistance of 10MΩ or less is a practical measurement resistance. This material can be easily mass-produced from inexpensive raw materials using ordinary ceramic synthesis technology.

The details of this invention will be explained below using examples. Table 1
shows the starting materials, calcination temperatures, firing temperatures, and chemical formulas of the resulting ceramics, listing nine types of ceramics as two representative examples. Since the synthesis method is almost the same, 4
N in Table 1 as a representative.

3, No., and H will be described.

Example 1 As starting materials, dian-enium phosphate NH4HPO4 of 99.91 or more, calsila carbonate Acaco3 and sodium carbonate Na2co5 are weighed out in a molar ratio of 1:1:0.5 and mixed in a ball mill for 2 hours. This was placed in a quartz crucible and fired at 900° C. for 1 hour in the air. At this stage, a bowl of orthorhombic NaCaPO4 is obtained. This is crushed and passed through a 400 mesh sieve. Obtained NaCa
Powder of PO4 was heated vertically to 350 at a pressure of 9/crIL2.
Press to a length of 10mm and a thickness of 11nl. The pressed product is placed in an electric furnace and fired in the atmosphere at 1100°C for 2 hours. After cooling, it is polished to a thickness of 400 μm. Next, as shown in FIG. 1, a perspective view of a moisture-sensitive element using a moisture-sensitive material according to an embodiment of the present invention, ruthenium oxide ('Ru0z) Porous electrode (2a),
(2b) is printed, platinum lead wires (3a) + (3b) are bonded using the same RuO2 paste, and then baked at 800° C. for 10 minutes to obtain a moisture-sensitive element.

Example 2 Reagent grade BaHPO4 and Na2 as starting materials
co3 in a molar ratio of 2:1, and
Mix for an hour. Put this into a quartz crucible.

Calcinate at 900°C for 1 hour in the air. As shown in Table 1, the tentative temperature varies depending on the composition of the ceramic.

Crush the calcined Tan Qiumono and pass it through a 4QQ mesh sieve.
-(NaBBPO4 powder is obtained. This is 350 Ky/
Press to a thickness of 1711 mm and a pressure of 10 cm2.

The pressed product is placed in an electric furnace and fired at 1100'C in the atmosphere for 2 hours. This firing temperature is the same as the calcination temperature in Table 2.
As shown in , it varies depending on the composition of the ceramic. After polishing the fired product to a thickness of 400 μm, porous electrodes (2a), (2
Print b) and bake at 750'C for 10 minutes. Lead wires (3a) and (3D) are soldered to this to obtain a moisture sensing element.

Above, No.3. We have described the manufacturing method of an element using the moisture-sensitive materials shown in Table 1. Next, we applied 1 volt to the lead wires (3a) and (3b) of the element using the moisture-sensitive materials shown in Table 1.

The dependence of the electric resistance value of the device on relative humidity (humidity sensitivity characteristics) when a sine wave of 1 KHss is applied is shown in FIGS. 2 to 5. The temperature is 30°C. aυ~α4Fi in Figure 2
These are the characteristics of the elements N011 to N004 in Table 1, respectively. High sensitivity of N a M g P O4. I in Figure 3
~ae are the characteristics of the elements No. 4 to No. 006 in Table 1, respectively. LiMgPO4 has high sensitivity, but KMgPO4 has the advantage of low resistance. Figure 4 a! 9. a7
).

Os has the characteristics of the elements NO, 5, 7, and 8 in Table 1, respectively, and has a higher resistance than LiZnPO4, LiCdPO4dLiMgPO4. 1ll-Jυ in FIG. 5 are the characteristics of the elements No. 009 to No. 11 in Table 1, respectively. Fifth
As shown in the figure, even if A and M of AMPO4 are combined, A is obtained.

There is no big difference in the characteristics from No. 1 to No. 8 in which M is composed of a single element.

Example 3 A humidity sensing element with another configuration using the humidity sensitive material of the example of the present invention is used, in which 99.9% or more of dibasic calcium phosphate CaHPO4 and sodium carbonate H are used as starting materials.
Weigh out a2CO5 at a molar ratio of 1:0.5 and mix in a ball mill for 2 hours. Put this in a quartz crucible,
After calcining at 1000° C. for 1 hour in the air, it was crushed and passed through a 400 mesh sieve to obtain NaCaPO4 powder. This is molded into a disk having a diameter of 20 nm and a thickness of 2 lll under a pressure of 350 Ky/cm 2 and fired in the air at 1100° C. for 2 hours. After polishing one surface, a porous ceramic Na Ca P 04 substrate (1) is prepared, as shown in FIG. On the polished side of the sieve electrode (4a) with silver-palladium paste.

(4b) is printed, baked at 850° C. for 10 minutes, and a lead wire (sa) + (5b) is soldered thereto to obtain a moisture-sensitive element.

In FIG. 7, the logarithm of the sieve electrodes (4a) and (4b) of the moisture sensing element shown in Example 3 is 8. Electrode spacing 400μm
, shows the humidity sensitivity characteristics when the length of the counter electrode is 5 lengths. Compared to the humidity sensitivity characteristics of Example 1, an element with almost the same sensitivity is obtained except that the resistance is slightly higher.

(Figure T shows the humidity-sensing characteristics of the humidity-sensing element obtained in Example 1.) Based on the humidity-sensing characteristics, the elements described above have electrical resistance values in the relative humidity range of 10 to 99 degrees. It can be seen that the change in is almost linear, and the change is three orders of magnitude, indicating good sensitivity. In addition, the response time when the relative humidity changes from 0% to 50 inches is within 2 seconds, and the humidity display error due to repeated measurements is within 3 inches, which poses no practical problem.

〔Effect of the invention〕

As explained above, this invention is a ceramic represented by the chemical formula AMPO4 (where A is an alkali metal L).
2M consisting of at least one of i, Na and K
is composed of one of the divalent metals Mg, Ca, Sr, Ba, Zn and Cd. ) is used as a main component to create a new sensor with high reliability, good sensitivity, and ease of mass production necessary for controlling relative humidity in the range of 10 to 99 degrees, which is a practical problem. A wet material can be obtained and used, for example, in sensors for air conditioners.

[Brief explanation of drawings]

FIG. 1 is a perspective view of a moisture-sensitive element using a moisture-sensitive material according to an embodiment of the present invention, and FIGS. 2 to 5 show moisture-sensitive characteristics of a moisture-sensitive element using a moisture-sensitive material according to an embodiment of the present invention. figure. FIG. 6 is a front view of a humidity sensing element having another structure using a humidity sensing material according to another embodiment of the present invention, and FIG. 7 is a moisture sensitivity characteristic diagram of the humidity sensing element of FIG. 6. +11 is a ceramic substrate, (2a), (2b) U
Porous electrodes, (3a) and (3b) lead wires, (4a) and (4b) sieve electrodes, (5a),
(5b) are lead wires. Note that the same reference numerals in the figures indicate the same or equivalent parts. Agent Masuo Oiwa Figure 1 Figure 2 λ eye vs. warming (γ0 Figure 3 vs. La display (γ・) Figure 4 I!1 Relative humidity & (γ.) Figure 5 X eye Fried humidity return ( γ・) Figure 6a Figure 7 λth Sentence) Yo! ! (chi 4)

Claims (1)

[Claims] Ceramics represented by the chemical formula AMPO4 (however, A
is the alkali metal L1. Consisting of at least one of Na and K, 2M is a divalent metal MgrCa, Sr, Ba,
It consists of at least one of zn and cd. )
A moisture-sensitive material whose main ingredient is