JPS58200502A - Moisture measuring element - 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 measuring element useful for measuring humidity by detecting changes in humidity as changes in electrical resistance. In particular, the present invention has excellent responsiveness in which the electrical resistance changes in response to changes in humidity, and the changes in electrical resistance that follow changes in humidity show a practically appropriate rate of change, for example, when the relative humidity is about 90~90. In a range of about 30%, the electrical resistance is about 1
It shows the appropriate order of 0' to 106Ω, and
1-Regarding a humidity measuring element that is inexpensive and easy to manufacture.

More specifically, the present invention relates to a humidity measuring element comprising a heat-treated composite metal oxide structure made of (a) lithium, (b) niobium, and (c) iron.

Conventionally, there are many humidity measuring elements, such as those in which a porous matrix is infiltrated with an aqueous electrolyte solution, and those in which metal oxides are heat-treated.

An example of a humidity measuring element in which a porous matrix is infiltrated with an electrolyte aqueous solution is one in which lithium chloride is used as the electrolyte aqueous solution.

The element of this example has a resistance value of 10 7 Ω to 10 3 Ω and is easy to use in practice for intermediate humidity between 40% RH and 80% RH. However, the upper limit of the operating temperature is low, for example 35
Even if it is left at temperatures above °C for 6 months, its characteristics will change significantly. In addition, when the humidity is high, the salt flows out due to the promotion of deliquescence, making it unusable.

Humidity measuring elements made of heat-treated metal oxides are physically, chemically, and thermally stable, but they generally have high specific resistance, making it difficult to detect with high precision even if there is a change in resistance due to moisture absorption and desorption phenomena. There are drawbacks.

As an example of a humidity measuring element in which such a metal oxide is heat-treated, Japanese Patent Application Laid-Open No. 55-2 uses a single crystal of LiNb01.
The proposal of No. 2122 is known. In this proposal, ferroelectric LiNb0. A humidity measuring element has been proposed in which an electrode is attached to a crystal and humidity is measured from the electrical resistance of the electrode. However, the use of such a single crystal has the disadvantage that the production of the single crystal itself is complicated and expensive, and its practical use is subject to various restrictions.

Instead of using such a single crystal, there is also a research report on an element in which a paste mainly composed of LiNbO1, which is a mixture of LiNbO5 powder and glass powder, is applied onto an alumina substrate, dried, and fired. (42nd Japan Society of Applied Physics Academic Conference, Proceedings, 8p-W-6, 7
95 pages, October 1982). According to this report, it is stated that in this element, LiPbNb0= is formed by utilizing the reactivity between LiNbO3 and circle]0 contained in the glass.

Furthermore, JP-A No. 56-23702 describes LiNb0. A moisture-sensitive resistor element body made of porcelain whose main component is at least one component selected from a wide range of metal oxides including Smaller than the wet resistance value range and 1Ω/
A humidity-sensitive resistor element has been proposed, which includes a pair of humidity-sensing electrodes made of a resistive heating element having a sheet resistance of 100 mL.

As specified in the above configuration, this proposal requires an electrode made of a resistance heating element that heats the humidity-sensitive resistor element body, and is complicated in structure and manufacturing and requires heating of the element body. There is profit.

The present inventors have been conducting research on the development of a humidity measuring element for a heat-treated composite metal oxide structure of lithium and niobium.

3- As a result, although the composite metal oxide heat-treated structure made of lithium and niobium has high electrical resistance, (
The electrical resistance of the composite metal oxide heat-treated structure consisting of a)'j thium, ()]) niobium, and (c) iron decreased significantly to about 103 in the range of about 90 to about 30% (R11). ~
It has been discovered that the change in electrical resistance following the change in humidity shows a practically appropriate rate of change, which is on the order of 106Ω, which is a practically appropriate order. Furthermore, it has been found that according to the present invention, a humidity measuring element that can achieve the above benefits without requiring heating of the element can be provided.

The above objects and many other objects and advantages of the present invention will become more apparent from the following description.

The humidity measuring element of the present invention comprises at least (a) lithium;
A composite metal oxide heat-treated structure containing (b) niobium and (c) iron is provided with at least one pair of electrodes.

According to a preferred embodiment, the humidity measuring element of the present invention comprises the (
a) Lithium, (b) niobium and (c) iron converted to metal atoms, (,) lithium 0.01-75 at% (b
) Niobium 20-99.98 atomic% (c) Iron
()・, 01~1() atomic% [However, (a) + (b
) + (c)'' 10 (l original f% 1 composite metal oxide heat-treated structure) A humidity measuring element provided with this pair of electrodes can be exemplified.

41 The humidity measuring element of the present invention can be a heat-treated structure from a system containing further metal oxides as carriers, which lends itself to the formation of more economical and industrial heat-treated structures.

Such carrier metal oxides include Al 203.5
i02 etc. can be exemplified. As for the amount, for example, violet may be used in which the total of (a), (b), and (c) is 0.1% by weight or more based on the carrier metal oxide.

In the examples, Li2C01, Nb2O5 and Fe are used as starting materials for the heat-treated structure constituting the humidity measuring element of the present invention.
Although zO3 is used, the combination is not necessarily limited to this. It is sufficient that the heat-treated structure contains at least lithium, niobium, and iron.

For example, as a lithium raw material L; 20, I=i=COs
, Li(-)11, L i HCO3, L ! C.I.
, LiCl0. , LiBr, Lil, liF, Li2
5O,, LiH3O,, LiN0= , LiNH
,,1,i old I, ,Li2S,LiH,Li=N,
By reducing Li2C2, C:O, Li, etc., the weight can be reduced. These can be used alone or in combination1, and as niobium raw materials, NbO, NbO2, Nb2O,...
b((',)It), NbBr3, NbFs, N
Examples include bH, NbC, and NbN. These can be used alone or in combination.

Furthermore, as an iron raw material, Fe01F e =, 03, Fe
,O,,Fe(CO):(NO),FeBr2,FeB
r2, Fe(NOz)2, Fe(,N03)3, Fe(
011):,,l' e(OH)3,FeC0,,Fe
(C5N,)2,FeF2,FeF3,l' e S
etc. 5- can be exemplified. These can be used alone or in combination.

The powder of the composite metal oxide heat-treated structure in the present invention is obtained by accurately weighing, for example,
It ends with obtaining a modified powder by calcination at a post-curing temperature and subsequent crushing. Also, in this firing, any 2
A modified powder can also be obtained by calcining the powder, adding the remaining metal oxide, calcining it again, and then pulverizing it. A binder may or may not be added to the adjusted powder as necessary, and the adjusted powder may be molded by pressure molding or non-pressure molding and then heat treated at a temperature of 900°C to 1300°C. An example of the humidity measuring element is a composite metal oxide heat-treated structure provided with at least one pair of electrodes. Also, L i 2CO,, Nb2O5)”ez
An example of a humidity measuring element is shown in which a pair of electrodes is provided on a composite metal oxide heat-treated structure obtained by accurately weighing o3, thoroughly mixing and pulverizing it in a ball mill, molding it, firing it, and then heat-treating it. can do. The heat treatment temperature for heat-treating such a powder mixture system to form a heat-treated structure is approximately 00°C to approximately 130°C (1'(
An example is the temperature of :. In addition, the powder particle size of the powder mixture system can be selected as appropriate, for example, approximately (), 1
Examples include particle sizes of 11L average particle diameter, such as ~21) 0 microns.

Also, when press-molding into the desired shape, or
As for the pressure conditions during the pressure forming heat treatment, for example, about 5
Molding pressures such as 0 Ky/d to about 2000 Ky/d can be exemplified.

The heat-treated structure constituting the humidity measuring element of the present invention is shaped like r&
According to another aspect, a preformed composite oxide comprising two metal components such as (a) lithium, (b) niobium, and (c) iron, and the remaining metals. (a), (b) by pulverizing the compounds individually and mixing them, or by co-pulverizing them using, for example, a ball mill, a vibration mill, or a suitable pulverizing and mixing means.
A powder mixture system containing (c) is prepared, mixed with an appropriate binder if desired, and molded into a desired shape to obtain a molded product of a desired shape, which is pre-fired or then heat-treated and fired. By doing so, a heat-treated structure can be obtained.

Also, according to another embodiment, in the powder mixture system as described above,
Application I: A slurry or paste mixture is formed by blending a suitable type and amount of binder to form a suitable slurry or paste, and this is mixed with alumina, beryllia, silica, 7-orsterite, etc. , steatite, mullite, magnesia, norconia, Cornolite Y, silicon nitrogen, boron nitride, etc., to form a film of about 0.001 to about 1 am, for example,
This can be heat treated under the heat treatment conditions as exemplified in 1) 1j to form a heat treated structure on the substrate-1.

Further, examples of the binder used in the above embodiment include polyvinyl butyral, polymethyl methacrylate, etc. 7-Tyl methacrylate copolymer, polyethyl acrylate, ethyl acrylate copolymer, polyvinyl chloride, polyvinyl acetate, polyvinyl alcohol, polyacrylamide, cellulose acetate', hexalatine, methyl cellulose, methyl ethyl cellulose, paraffin, Vaseline, etc. can be exemplified. A binder suitable for each aspect can be appropriately selected from among these, and a plurality of binders can be selected and used in combination.

The humidity measuring element of the present invention can be used by attaching electrodes by a method known per se. Examples of means for forming such electrodes include screen printing, coating, dipping, vapor deposition, and sputtering. Further, the shape of the electrode can be selected as appropriate, and for example, it can be provided in the shape of a comb-shaped electrode, a spiral electrode, or a parallel electrode. Examples of electrode forming materials include Au, At, I'd,
AH1A8 Metals such as Pd, Cu, Ni and I'< u
(,) 2.1 oxides such as acrO1 can be exemplified.

Hereinafter, some embodiments of the method of the present invention will be explained in more detail with reference to Examples.

Examples 1 to 6 and Comparative Example 1 l, i 2 C03, N b shown in Table 1 below:
(-), )er, and 03 were weighed out, ground, and mixed in the molar percentages shown in the table. Approximately 900 millimeters of the second grinding mixture system
A preheating treatment was carried out for about 11 hours at a temperature of '(:), and then these preheated products were ground +1+ in a ball mill to obtain a prepared powder. 5 wt % of paraffin of the prepared powder was added as a binder to the prepared powder and mixed, and 1) a disk-shaped sample having a diameter of 20 u and a thickness of about 1 H was press-molded at a pressure of 1) mm/i. The disc-shaped sample was
Heat treatment was performed for about 1 hour at a temperature set at 00°C to 1300°C to obtain a composite metal oxide heat-treated structure. Comb-shaped electrodes were printed on the composite metal oxide heat-treated structure using gold paste using a clean printing method, and baked at a temperature of about 850°C for about 45 minutes to form a pair of comb-shaped gold electrodes. Formed.

Comparative Example 2 In Comparative Example 2, a pair of comb-shaped gold electrodes were formed on a single crystal of l-,iNlIO3, a composite metal oxide consisting of lithium and niobium.

Using a standard circuit, we measured the characteristics of relative humidity versus electrical resistance of a sample consisting of a composite metal oxide heat-treated structure provided with a pair of comb-shaped gold electrodes, and determined the resistance value at 25°C and 40% R1-1. R
The resistance values R2 at 1 and 25° C. and 90% RH are shown in Table 1 along with the composition.

In addition, attached Figure 1 shows the results of Example 5 (line C in the figure), Comparative Example 1 (line b in the figure), and Comparative Example 2 (line a in the figure) in Table 1. 1. A characteristic curve of degree-electrical resistance (logarithm) is shown.

Furthermore, the term "humidity measuring element" as used herein is synonymous with "humidity sensing element" and "humidity sensing resistor element".

9- =10-

[Brief explanation of drawings]

Attached Figure 1 shows the people of Example 5, Comparative Example 1, and Comparative Example 2.
It is a graph which shows the relative humidity-electrical resistance value (logarithm) characteristic curve about /. =11-

Claims (1)

[Claims] 1. At least (+1) lithium, (b) niobium and (
c) A humidity measuring element comprising at least one pair of electrodes provided on a heat-treated composite metal oxide structure containing iron. 2. The (a) lithium, the (b) niobium, and the (c) iron are expressed in terms of metal atoms, (a) lithium 0.01-75 atomic% (b)
Niobium 20-99.98 atomic% (c) Iron
0.01 to 10 atomic% [However, (a) + (b) + (
c)" The humidity measuring element according to claim 1, which comprises a composite metal oxide heat-treated structure containing 100 atom %1.