JPS6255681B2 - - Google Patents

Description

[Detailed description of the invention]

The present invention relates to an electrical resistance type moisture sensing element that utilizes changes in electrical resistance due to humidity. Conventional electrical resistance type moisture sensing elements have a humidity sensing element (1).
Those using electrolyte salts such as lithium chloride, (2)
Fe ₃ O ₄ colloid, Fe ₂ O ₃ , Al ₂ O ₃ , Cr ₂ O ₃ and
Examples include those using metal oxides such as Ni ₂ O ₃ and (3) those using vapor deposited films of Ge and Se. Typical of these humidity sensing elements are those using lithium chloride and Fe ₃ O ₄ colloids, which have good linearity and sensitivity to humidity and have been used as humidity sensing elements for measuring instruments. However, since the moisture-sensitive element described above has a film-like structure, it is easily affected by the manufacturing conditions (film thickness, coating method, heat treatment, etc.) during the production of the element, which tends to cause variations in characteristics and performance, resulting in poor reproducibility and Because this resulted in a decrease in yield, it required a great deal of skill to manage the manufacturing conditions. In addition, the humidity sensitive element changes relatively significantly over time, requiring periodic calibration and readjustment. Therefore, it is unsuitable for uses other than devices that can be calibrated and readjusted, such as measuring instruments, and cannot be used for products that cannot be periodically calibrated, such as home appliances. An object of the present invention is to eliminate the above-mentioned drawbacks of the prior art, and to provide a moisture-sensitive element made of a sintered body that is easy to manufacture, has small performance variations, has a good manufacturing yield, and has good long-term reliability. It is in. The above purpose is to use Al,
This is achieved by using a sintered body containing composite oxides of Fe and Co as essential components. The present invention will be explained in detail below using examples. Using aluminum oxide (Al ₂ O ₃ ), iron oxide (Fe ₂ O ₃ ) and cobalt oxide (Co ₂ O ₃ ) as raw materials,
After weighing to obtain a predetermined composition ratio, the mixture was placed in a pot mill together with ion-exchanged water, and wet-mixed for 15 hours using a conventional mixing method. After mixing, dehydrating and drying the material powder, the material powder is granulated and then temporarily molded (molding pressure: 80
~150Kg/ ^cm3 ) and temporarily molded products at 900~1000℃.
Temporary firing is performed for 2 hours. After calcining, the material is coarsely pulverized and finely pulverized (pot mill method) using a commonly used method, dehydrated and dried to produce a calcined powder material.
The obtained material is granulated by adding a binder (e.g. polyvinyl alcohol, etc.) and ion-exchanged water in a predetermined amount, and then molded into a disc shape with a diameter of 9 mm and a thickness of 1 mm at a molding pressure of 500 to 850 Kg/ ^cm3. manufacture the body. This molded body was fired at 1,050°C to 1,400°C for 2 hours to obtain a moisture-sensitive body for a humidity-sensitive element. On both planes of the obtained humidity sensitive body,
Apply RuO ₂ electrode material with sheet resistance 10Ω, 800~
The moisture-sensitive element shown in Figure 1 was completed by baking at 900°C for 10 minutes. The moisture sensing element manufactured by the above method had good thermal stability because it was a sintered body sintered at a high temperature, and it was a highly reliable moisture sensing element with little change over a long period of time. Moreover, since the manufacturing method of the moisture sensitive element does not require particularly difficult manufacturing techniques and can be similar to the manufacturing method of ordinary ceramic materials, it is possible to reduce the variation in performance of the moisture sensitive element due to manufacturing technology and the reproducibility of characteristics. No problems occurred and the manufacturing yield was good. Moisture-sensitive elements having the compositions shown in Table 1 (compositions are expressed by the metal atomic molar ratio of each material) were manufactured using the manufacturing method shown above, and the moisture-sensing characteristics were measured. As shown in FIG.
In Figure 2, straight lines 3, 4, 5,...13, 14
and 15 are sample Nos. 1 and 2 shown in Table 1 above,
3..., 11, 12 and 13 are shown. Also, in Fig. 3, straight lines 16, 17,
18, 26, 27 and 28 are the samples shown in Table 1 above, 14, 15, 16, 24, 25 and 26

【table】

【table】

【table】

[Table] This table shows the humidity-sensitive characteristics of the humidity-sensitive element. Next, Table 2 shows the moisture sensitivity coefficient of each moisture sensing element:
β, temperature dependence: α/β. In addition, moisture sensitivity coefficient: β and temperature dependence: α/β
was calculated from the measurement results using the following formula. However, p ₁ : Resistivity of the humidity sensing element at relative humidity RH ₁ (%) p ₂ : Resistivity of the humidity sensing element at relative humidity RH ₂ (%) However, p ₁ : Resistivity of the humidity sensing element at temperature T ₁ (°C) p ₂ : Resistivity of the humidity sensing element at temperature T ₂ (°C) Moisture sensitivity coefficient in Table 2: β and temperature dependence Characteristics: For general purposes, if α/β is in the range of β≧3 and α/β≦0.3, it can be used without the need for temperature compensation. FIG. 4 shows the composition of the moisture-sensitive element samples shown in Table 1 in a commonly used composition triangular diagram. In the compositional triangular diagram of FIG. 4, the numerical values written in the circles correspond to the sample numbers shown in Table 1 above. As explained above, if a sintered body with a composition within the range surrounded by the dotted line in the composition triangular diagram of Fig. 4 is used as a humidity sensing element, the moisture sensitivity coefficient: β and the temperature dependence: α/β β≧3, α/β≦, respectively
0.3 and can be used as a good moisture-sensitive element. That is, in the range surrounded by the dotted line 29 in the compositional triangular diagram described above, in other words, in the compositional triangular diagram expressed by the atomic molar ratios of Al, Fe, and Co, the atomic molar ratio is Fe/Al=0.091, Co /Al=0
.091, Co/Al =2, Fe/Co=0.5, Fe/Co=2.0 and Fe/
When the composition points where Al=5 are successively connected with a straight line, this corresponds to the range surrounded by the straight line (including the composition where the molar ratio is on the straight line). For compositions outside of this range, moisture sensitivity coefficient: β
is β<3 or the resistivity is 10 ⁸ Ω-cm or more, making it unsuitable and unsuitable for use as a moisture-sensitive element for general use. Next, to confirm reliability, a high temperature and high humidity test (temperature
60℃, relative humidity 95% RH) The results are the 5th.
It was as shown in the figure. In Figure 5, curves 30, 31, 32, 3
3, 34, 35, 36, 37, 39, 40, 41
and 42 are samples No. 1, No. 3, No. 5, No. 8, No. 14, No. 16, and No. 23 shown in Table 1 and Table 2 above.
,
It shows the rate of change in characteristics of the moisture sensitive elements No. 25, No. 27, No. 28, No. 29, and No. 30, and it can be seen that they are stable over a long period of time and have little deterioration. In addition, in Fig. 5, curve 38 is the rate of change in characteristics of a conventional humidity sensing element (using Fe ₃ O ₄ colloid) used for comparison. Although only representative examples are shown in the figure, similar good results were obtained with moisture-sensitive elements having compositions not shown. As mentioned above, the use of a sintered body containing at least two or more types of composite oxides among the oxides of Al, Fe, and Co as a moisture sensing element has traditionally caused problems. There is no variation in characteristics or performance due to the manufacturing process, and there is no decrease in yield.
Moreover, it has the advantage that a stable moisture-sensitive element with little change over time can be obtained, and can be used in applications such as home appliances that cannot be calibrated or readjusted.

[Brief explanation of the drawing]

FIG. 1 is an example of the structure of a moisture-sensitive element according to the present invention, FIGS. 2 and 3 are diagrams showing the moisture-sensitive characteristics of the moisture-sensitive element according to the present invention, and FIG. 4 is a composition showing the scope of the present invention. The triangular diagram and FIG. 5 are examples of reliability test results for the moisture-sensitive element according to the present invention. 1: Moisture sensitive body, 2, 2': Electrode material.

Claims (1)

[Claims] 1 A composite oxide which is a sintered body of oxides of Al, Fe and Co, and in which the atomic molar ratio of metal atoms in the composite oxide is equal to or less than Fe/Al in the composition triangular diagram. =0.091, Co/Al=0.091, Co/Al=2, Fe/
1. A moisture-sensitive element characterized by being within a range surrounded by connecting the composition points of Co=0.5, Fe/Co=2.0 and Fe/Al=5.