JPS5811721B2 - Kanshitsusoshi - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a humidity sensing element that is made of an oxide semiconductor and detects humidity as a change in electrical resistance.

As is well known, metal oxides (Fe304tFe20
3#A403pCr203, etc.) have excellent water absorption properties and can be used as moisture-sensitive elements.

In other words, it takes advantage of the fact that the electrical resistance of a layer formed by depositing this type of metal oxide fine powder on the surface of an inorganic insulating substrate with a pair of opposing electrodes changes significantly in response to changes in humidity. It is.

Moisture-sensing elements using fine powders of the metal oxides mentioned above are physically, chemically, and thermally stable, but they generally have a high specific resistance, so even if there is a slight change in resistance due to moisture absorption and desorption phenomena, this will not occur. It is difficult to detect electrically with high precision.

Therefore, several attempts have been made to lower the resistivity. For example, alkali metal oxides (Li, 0pK20j
Addition of Na20, etc.) has been carried out.

However, in this case, there are disadvantages that not only the humidity cycle history becomes significantly large, but also that reproducibility is poor and changes over time are large.

Accordingly, the present invention aims to provide a moisture-sensitive element in which the above-mentioned drawbacks are eliminated.

Hereinafter, the moisture sensitive element of the present invention is LiMeMn04 (Me=A
At least one selected from tpCo, Cr, Fe, and GayRh) is used, and L
A sintered body having a composition of iMeMn045 molt or more (but not including 100 molt) and Zn095 molt or less (but not including 0 molt) is used.

That is, the moisture sensing element of the present invention is an oxide film having a pseudo-spinel structure, which is obtained by sintering at least one of aluminum oxide, cobalt carbonate, chromium oxide, iron oxide, gallium oxide, and rhodium oxide, as well as lithium carbonate and manganese carbonate. At least one pair of electrodes is provided on the sintered body obtained by press-forming and sintering the sintered body, which is made mainly of aluminum oxide, mixed with zinc oxide if necessary.

By adding ZnO, the resistance value of the sintered body can be lowered and controlled to a desired value.

However, when adding and mixing the ZnO component, the composition ratio must be selected to be 95 molti or less.

The reason for this is that if the composition ratio of ZnO is 95 molar or more, the range of change in resistance value with respect to humidity becomes small, making it unsuitable for practical use.

In the present invention, LiMeMnO4 powder which is the main component is Li2CO3sMe20Li2C03s, Co.

at least one of CreFe and GatRh).

and MnCO3 in a molar ratio of 1=2:20, mixed well in a ball mill, pre-calcined at a temperature of 700 CI degrees for about 1 hour, and pulverized.

Therefore, the sintered body of the moisture-sensitive element of the present invention is made of the above-mentioned LiMeMn
It can be obtained by adding and mixing ZnO powder alone or LiMeMn04 powder and press molding and firing.

Next, the present invention will be specifically explained.

First, Lt2CO3sMe203 (Me=AttCQsC
ryFesGa, Rh) and M
nCO3 was accurately weighed out to a composition ratio of 1:2:2 in terms of molar ratio, and thoroughly mixed using a ball mill.

Thereafter, this mixture was pre-calcined at 700°C for 1 hour and then ground in a ball mill to obtain LiMeMn04 (
At least one of Me=AIaCO#Cr#Fe5Ga and Rh) was obtained.

The thus obtained LiMeMn04 powder and ZnO powder were selected and mixed in the composition ratios (molti) shown in the following table to prepare 50 types of raw materials including comparison ρ.

Next, polyvinyl alcohol (binder) is added to the raw material powder.
was added and press-formed at a pressure of 1 ton/dm2, then 80
A disk-shaped sintered body having a thickness of 1 m and a diameter of 20 mm was obtained by heating and sintering at a temperature of 0 to 1300°C for 2 hours.

A silver paste was baked on the main surface of this disc-shaped sintered body, a pair of electrodes were provided, and lead wires were soldered to each to produce moisture-sensitive elements.

FIG. 1 is a plan view of the above-mentioned moisture-sensitive element, in which 1 is a sintered body, 2.7' is an electrode, and 3.3' is a lead wire.

The relationship between the relative humidity and the resistance value for each of the moisture-sensitive elements obtained as described above is shown in the table together with the composition ratio.

Further, FIG. 2 shows the relative humidity-resistance value characteristics of the example row 31.

No deviation due to humidity cycles was observed, indicating stable customization.

For reference, FIG. 2 also shows the case of the magnetite colloid type as a conventional column.

Further, Examples 13 and 33.42 were left for 1000 hours at 40° C. and 95% relative humidity, and changes in characteristics (resistance value-humidity relationship) over time were determined, as shown in FIG.

As is clear from the figure, LiMeMn0 according to the present invention
4 type moisture sensing elements show almost no change in resistance value,
It is also stable over time.

As described above, the humidity sensing element according to the present invention always exhibits the required characteristics, does not deviate due to humidity cycles, and has a large resistance change with respect to humidity changes, so it is useful for accurately measuring humidity. It can be said that it brings many practical advantages in combination with ease of manufacture and ease of handling.

[Brief explanation of the drawing]

FIG. 1 is a plan view showing a configuration row of a humidity sensing element according to the present invention, FIG. 2 is a characteristic diagram showing an example of the relationship between relative humidity and resistance value for the humidity sensing element according to the invention, and FIG. FIG. 2 is a diagram showing a series of temporal characteristics of the moisture-sensitive element according to the present invention.

Claims (1)

[Claims] I LiMeMn04CMe=Al, CapCryFe
A moisture sensing element comprising at least one pair of electrodes provided on a sintered body made of at least one type selected from eGasRh. 2 Sintered body with a composition of LiMeMn045 molti or more (but not including 100 molti) and Zn095 molti or less (but not including OMoA%) (Me = At least one selected from At, Co, Cr. Fe#GazRh) A moisture sensing element comprising at least one pair of electrodes.