JP2911292B2 - Humidity sensor - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a humidity sensor for detecting a ratio of water vapor in air based on a change in electric resistance of a humidity sensing element.

[0002]

2. Description of the Related Art The principle of humidity sensitivity of a humidity sensor is roughly classified.
Using the change in electrical resistance due to the adsorption of water molecules
There are two types:
Many humidity sensors that use a laser material use the former principle.
doing. In addition, conventionally, the ceramic material of the moisture sensitive part,
Al_TwoO_Three, ZrCr_TwoO_Four, MgCr_TwoO_Four-TiO
_Two, ZrO_TwoA humidity sensor using such as has been developed.

[0003]

However, the above-mentioned conventional humidity sensor has a drawback that if it is used for a long period of time, its humidity-sensitive characteristics change and it becomes impossible to measure the humidity accurately.
An object of the present invention is to provide a humidity sensor that can maintain the same characteristics for a long period of time and has little change over time.

[0004]

In order to solve the above-mentioned problems,
The present invention employs the following configuration. (1) A pair of electrodes and a moisture-sensitive element arranged so as to be in contact with both of the electrodes, and the electric resistance value between the electrodes due to the adsorption and desorption of water vapor in the air to and from the moisture-sensitive element. In a humidity sensor that detects a ratio of water vapor contained in the air from a change, the moisture-sensitive element includes a sodium element,
It is a porous ceramic in which various kinds of solid solutions containing silicon element, oxygen element and rare earth metal element as main components are mixed. (2) a pair of electrodes and a moisture-sensitive element arranged so as to be in contact with both of the electrodes, and the electric resistance value between the electrodes due to the adsorption and desorption of water vapor in the air to and from the moisture-sensitive element. In a humidity sensor that detects a ratio of water vapor contained in the air from a change, the humidity-sensitive element has a calcined composition ratio,
1 mol% to 45 mol% sodium monoxide, trace amount to 45 mol%
Mole% oxide of rare earth metal element, and 1 mole% to 6 mole%
This is a porous ceramic manufactured using a calcined material composed of 5 mol% of silicon dioxide. And (3) a pair of electrodes and a moisture-sensitive element arranged so as to be in contact with both of the electrodes, and the electric resistance value between the electrodes due to the adsorption and desorption of water vapor in the air to and from the moisture-sensitive element. In a humidity sensor that detects a ratio of water vapor contained in the air from a change, the humidity-sensitive element has a calcined composition ratio,
1 mol% to 45 mol% sodium monoxide, trace amount to 45 mol%
Mole% oxide of rare earth metal element, and 1 mole% to 6 mole%
This is a porous ceramic manufactured using a calcined body obtained by adding and mixing an appropriate amount of phosphorus or a phosphorus compound to a calcined product composed of 5 mol% of silicon dioxide and recalcining.

[0005]

[Action and effect of the invention]

[Claim 1] An electric resistance value between electrodes due to the provision of a pair of electrodes and a moisture-sensitive element arranged so as to be in contact with both of the electrodes, wherein water vapor in the air absorbs and desorbs from the moisture-sensitive element. In the humidity sensor of the humidity sensor that detects the proportion of water vapor contained in the air from the change in
Oxygen element, and the use of porous ceramics mixed with various types of solid solutions mainly composed of rare earth metal elements,
Although the theoretical operation is unknown, the humidity sensor is unlikely to cause the time-dependent change of the humidity-sensitive characteristics, so that the humidity sensor can maintain the same characteristics for a long time. [Claim 2] The composition ratio of the calcined product is 1 mol% to 45 mol%.
A porous ceramic manufactured using a calcined substance composed of mol% sodium monoxide, a trace amount to 45 mol% of an oxide of a rare earth metal element, and 1 mol% to 65 mol% of silicon dioxide is used for a humidity sensor. When used in a humidity-sensitive element, the theoretical function is unknown, but the humidity-sensitive element is unlikely to cause a change with time in its humidity-sensitive characteristics, and its resistance value falls within a range suitable for humidity measurement. For this reason, the humidity sensor can maintain the same characteristics for a long period of time and can easily perform humidity measurement. If the composition ratio of the calcined product of sodium monoxide exceeds 45 mol%, deterioration with time becomes severe, and if it is less than 1 mol%, the resistance value at low humidity is high. If the composition ratio of the calcined product of the oxide of the rare earth metal element exceeds 45 mol%, the resistance value increases over the entire range, and the resistance value becomes extremely high even at high humidity. On the other hand, if the ratio is zero, the sinterability deteriorates and the strength decreases. If the calcined composition ratio of silicon dioxide exceeds 65 mol%, the resistance value increases over the entire range, and the resistance value becomes extremely high even at high humidity. On the other hand, if the ratio is zero, the sinterability deteriorates and the strength decreases. [Claim 3] The composition ratio of the calcined product is 1 mol% to 45 mol%.
An appropriate amount of phosphorus or a phosphorus compound is added to a calcined product composed of mol% of sodium monoxide, a trace amount to 45 mol% of an oxide of a rare earth metal element, and 1 mol% to 65 mol% of silicon dioxide, and mixed, When a porous ceramic manufactured using the recalcined calcined body is used for a humidity sensor of a humidity sensor,
Although the theoretical operation is unknown, the humidity-sensitive element is unlikely to cause the time-dependent change of the humidity-sensitive property, and its resistance value falls within a range suitable for the humidity measurement, and the linearity of the humidity-sensitive property is further improved. . For this reason, the humidity sensor can maintain the same characteristics for a long period of time, and can easily and accurately measure the humidity. If the amount of phosphorus or the phosphorus compound is out of the appropriate range, the rate of deterioration with time increases.

[0006]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS One embodiment of the present invention is shown in FIGS.
Explanation will be made based on the table. As shown in FIG. 1, the humidity sensor A includes an end face 10 of an alumina substrate 1 having electrical insulation.
The comb electrodes 2 and 3 and the moisture sensitive element 4 are sequentially laminated. Also, gold electrode extraction portions 5 and 6 are fixed to the ends of the comb-shaped electrodes 2 and 3, and lead wires 7 and 8 are electrically connected to the electrode extraction portions 5 and 6.

In the present embodiment, the alumina substrate 1 is a plate having a thickness of 0.6 mm, a length of 5 mm, and a width of 15 mm, and is formed of a ceramic sintered body mainly composed of alumina.

The comb-shaped electrodes 2 and 3 have a thickness of several tens of microns, and a ruthenium oxide (R)
uO ₂ ) is a thick film printed and baked.

The moisture-sensitive element 4 has a thickness of several tens of microns,
In addition to the sodium ion conductor in which the sodium element, rare earth metal element, silicon element, and oxygen element are three-dimensionally linked, various solid solutions containing sodium, silicon, oxygen, and the rare earth metal element as main components are mixed. , Exhibiting a microcrystalline porous structure. In the present embodiment, in order to manufacture the moisture-sensitive element 4, sodium carbonate (Na ₂ CO ₃ ) and silicon dioxide (SiO ₂ ), yttrium oxide (Y ₂ O ₃ ), lanthanum oxide (La ₂ O ₃ ) , Samarium oxide (Sm
₂ O ₃ ), gadolinium oxide (Gd ₂ O ₃ ), dysprosium oxide (Dy ₂ O ₃ ), holsium oxide (Ho ₂ O)
₃ ), any one of erbium oxide (Er ₂ O ₃ ) and ytterbium oxide (Yb ₂ O ₃ ) and selectively used ammonium dihydrogen phosphate (NH ₄ H ₂ PO ₄ ).

Next, a method of manufacturing the humidity sensor A will be described. {1} After calcination, sodium monoxide (Na ₂ O), an oxide of a rare earth metal element, and silicon dioxide (SiO ₂ )
Is mixed with predetermined amounts of sodium carbonate (Na ₂ CO ₃ ), an oxide of a rare earth metal element and silicon dioxide (SiO ₂ ) so that the composition ratio of
Calcinate at ~ 1000 ° C. {2} sample numbers 16, 18, 20, 22, 23, 25,
With respect to 27, 29 and 31, after the calcined product was pulverized, ammonium dihydrogen phosphate (NH ₄ H ₂ PO ₄ ) was added at the ratio shown in Table 1 and mixed, and calcined at 800 to 1000 ° C. Then, crush. In the case of other sample numbers, the calcined product is pulverized and subjected to {3}. {3} The above pulverized material is made into a paste. {4} This paste is printed on the alumina substrate 1 on which the comb electrodes 2 and 3 and the electrode extraction portions 5 and 6 have been baked in advance. {5} Integrated firing at 600 ° C to 900 ° C. {6} Platinum lead wire 7,
8 is attached, and the humidity sensor A is completed.

Table 1 Sample Rare Earth Total Number Na ₂ O Oxide of metal element SiO ₂ NH ₄ H ₂ PO ₄ Evaluation 180 Y ₂ O ₃ 10 10 − × 260 Y ₂ O ₃ 30 10 − × 360 Y _{2 O 3 10 30 - × 4} 40 Y 2 O 3 40 20 - 〇 _{5 40 Y 2 O 3 20 40} - 〇 _{6 30 Y 2 O 3 60 10} - × 7 30 Y 2 O 3 10 60 - 〇 8 20 Y ₂ O ₃ 40 40 -９ 910 Y ₂ O ₃ 80 10-× 10 10 Y ₂ O ₃ 60 30-× 11 10 Y ₂ O ₃ 3060-１２ 1210 Y ₂ O ₃ 1080-× 1342 Y ₂ O ₃ 1 57 - 〇 _{14 40 Y 2 O 3 10 50} - 〇 _{15 40 Y 2 O 3 6 54} - 〇 _{16 40 Y 2 O 3 6 54} 10 ◎ 17 40 La 2 O 3 6 54 - 〇 18 40 La _{2 O 3 6 54 10 ◎ 19} 40 Sm 2 O 3 54 - 〇 _{20 40 Sm 2 O 3 6 54} 10 ◎ 21 40 Gd 2 O 3 6 54 - 〇 _{22 40 Gd 2 O 3 6 54} 10 ◎ 23 40 Gd 2 O 3 6 54 30 × 24 40 Dy 2 O 3 6 54 - 〇 _{25 40 Dy 2 O 3 6 54} 10 ◎ 26 40 Ho 2 O 3 6 54 - 〇 _{27 40 Ho 2 O 3 6 54} 10 ◎ 28 40 Er 2 O 3 6 54 - 〇 29 40 Er ₂ O ₃ 6 54 10 ◎ 30 40 Yb ₂ O ₃ 654-３１ 3140 Yb ₂ O ₃ 6 54 10 ◎ ←←←← Numbers are% by weight →→→→ However, Na ₂ O, oxides of metal elements, and SiO ₂ NH ₄ H against the figures below precalcination composition ratio (mol%) the numbers under NH ₄ H ₂ PO ₄ is calcined product
₂ PO ₄ content (% by weight)

Next, a description will be given of a humidity sensitivity characteristic test of the humidity sensor A. Using a split flow type humidity generating tank, the relative humidity is changed at intervals of 6 minutes within a temperature range of 20 ° C. and a relative humidity range of 20% RH to 90% RH, and the impedance between the lead wires 7 and 8 is determined based on the LCR meter. Was measured. FIG. 2 shows the results of a humidity sensitivity test of the humidity sensor A using the sample numbers 16, 21, and 22. The humidity sensor A using gadolinium oxide (Gd ₂ O ₃ ) as the oxide of the rare earth metal element and using the sample No. 22 to which 10% by weight of ammonium dihydrogen phosphate (NH ₄ H ₂ PO ₄ ) was added showed a change in impedance. , And low hysteresis, sample numbers 1-31
Among them, it was found that the moisture sensitivity was most excellent.

Next, the change over time of the humidity sensor A will be described. The humidity sensor A manufactured using the moisture-sensitive element of Sample No. 22 was subjected to a measurement of 30% RH, 50% RH, and 90% RH during a room temperature operation test period of about 300 days, as shown in FIG. The drift was within ± 3%, and extremely stable characteristics were exhibited. A humidity sensor A manufactured using the moisture-sensitive element of sample No. 22 was subjected to an operation test for about 300 days under severe conditions of 40 ° C. and 95% RH. During the period, as shown in FIG. , 30% RH, 50% RH, and 90% RH, the drift was within ± 3%, showing extremely stable characteristics even under severe conditions. When a humidity sensor manufactured using the moisture-sensitive element of Sample No. 23 to which ammonium dihydrogen phosphate (NH ₄ H ₂ PO ₄ ) was excessively added was tested in the same manner, the results shown in FIGS. 5 and 6 were obtained. It was found that the change with time was much greater than that of Sample No. 22 with the proper addition (trace amount to 29% by weight). This is considered to be due to the chemical instability of phosphorus (P).

Next, the responsiveness of the humidity sensor A will be described. The temperature of the humidity sensor A manufactured using the moisture-sensitive element of the sample No. 22 was 20 ° C., the relative humidity was 50% RH, and the humidity was 90%.
FIG. 7 shows the measurement results of the response characteristics at the time of humidity increase and humidity decrease at% RH. As shown in the results of FIG.
It was confirmed that equilibrium was reached in about 140 seconds when the humidity and the humidity increased, and it was found that this humidity sensor A could be used without any practical problems.

[Brief description of the drawings]

FIG. 1 is an exploded view of a humidity sensor according to one embodiment of the present invention.

FIG. 2 is a graph showing a relationship between relative humidity and impedance of a humidity sensor manufactured using sample numbers 16, 21, and 22.

FIG. 3 is a graph showing a temporal change when a humidity sensor manufactured using a sample number 22 is operated indoors.

FIG. 4 shows a humidity sensor manufactured using Sample No. 22;
It is a graph which shows a time-dependent change at the time of operating at 40 degreeC and 95% RH.

FIG. 5 is a graph showing a temporal change when a humidity sensor manufactured using the sample number 23 is operated indoors.

FIG. 6 shows a humidity sensor manufactured using Sample No. 23,
It is a graph which shows a time-dependent change at the time of operating at 40 degreeC and 95% RH.

FIG. 7 shows a humidity sensor manufactured using the moisture-sensitive element of Sample No. 22 at a temperature of 20 ° C., a relative humidity of 50% RH and a humidity of 90%.
It is a graph which shows the measurement result of the response characteristic at the time of humidity increase and humidity reduction in% RH.

[Explanation of symbols]

 2, 3 Comb-shaped electrode (electrode) 4 Humidity-sensitive element A Humidity sensor

Claims (3)

(57) [Claims] 1. An electric resistance between a pair of electrodes and a moisture sensitive element arranged so as to be in contact with both of the electrodes. In a humidity sensor for detecting a ratio of water vapor contained in the air from a change in the value, the moisture-sensitive element contains a mixture of various types of solid solutions containing sodium element, silicon element, oxygen element, and rare earth metal element as main components. A humidity sensor characterized in that it is a porous ceramic. 2. A device according to claim 1, further comprising a pair of electrodes and a moisture-sensitive element arranged so as to be in contact with both of said electrodes. In a humidity sensor for detecting a ratio of water vapor contained in the air from a change in the value, the moisture-sensitive element may have a composition ratio of 1 mol% to 45 mol% of sodium monoxide and a trace amount of 45 mol% in a calcined material composition ratio. A humidity sensor characterized by being a porous ceramic manufactured using a calcined substance composed of an oxide of a rare earth metal element and 1 mol% to 65 mol% of silicon dioxide. 3. A device comprising a pair of electrodes and a moisture-sensitive element arranged so as to be in contact with both of the electrodes, and an electric resistance between the electrodes caused by water vapor in the air being absorbed and desorbed by the moisture-sensitive element. In a humidity sensor for detecting a ratio of water vapor contained in the air from a change in the value, the moisture-sensitive element may have a composition ratio of 1 mol% to 45 mol% of sodium monoxide and a trace amount of 45 mol% in a calcined material composition ratio. An appropriate amount of phosphorus or a phosphorus compound is added to a calcined product composed of an oxide of a rare earth metal element and 1 mol% to 65 mol% of silicon dioxide, mixed, and re-calcined to produce a porous body. A humidity sensor characterized by being a high quality ceramic.