JPS5960348A - Gas and humidity sensitive element - Google Patents

Abstract

PURPOSE:To detect selectively 0-100% relative humidity, malodorous gas and gaseous alcohols with high sensitivity, by constituting an element monolithically with an element substrate made of an apatite ceramic material and a metallic oxide between separation electrodes provided to said substrate. CONSTITUTION:Apatite hydroxide powder substituted 10% Ca by Na is formed and is calcined. Separation electrodes 2, 3 made of RuO2 paste are screen-printed on a sintered body 1 and also, an electrode 4 made of RuO2 paste which is pasted all over the surface is screen-printed on the rear surface of the sintered body 1. Next, titanium oxide TiO2 paste is screen-printed interposing the electrodes 2, 3. Thereafter, it is sintered after attaching lead wires 6, 8. A gas sensitive material is formed by TiO2 and it is necessary to keep the element at >=200 deg.C in case of detecting the gas. For that reason, it may be good to provide a kanthal wire coil heater around the element or to serve both as the heater and a humidity sensitive electrode by attaching two lead wires to the RuO2 electrode pasted RuO2 all over the surface.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to an element that detects malodorous gases such as methyl mercaptan (CH3SH) and hydrogen sulfide (H2S), alcohol gas, and humidity.

Measurement of concentrations of CJS) I, H2S, etc., which are the main components of bad odors generated at human waste treatment plants, garbage treatment plants, etc.

- This is done using an electrochemical method, but it requires gas sampling and requires a complicated side chamber.

Furthermore, conventional semiconductor gas sensors have insufficient sensitivity and have not been used.

Alcohol gas detection conventionally uses 5no2, ZnO
Many devices are used, such as those that utilize the change in electrical type conductivity due to gas chemisorption NVc of gold-patterned oxide semiconductors. However, they show the same phenomenon with other combustible gases such as methane, propane, carbon oxide, and hydrogen. That is, there is no selectivity for gas species.

On the other hand, depth sensing elements include metal oxides, inorganic and organic electrolytes, conductive materials,
Its simplicity, connectivity with microbroseturi, etc.)
It has been often used. Among them, metal oxides have low stability,
It is said to be preferable because it has good thermal properties.

Detects temperature with α degree, gas, and a single integrated element, and has stable moisture-sensing characteristics, and;, J! , ”, - Rigas, high m degree for alcohol gas, quotient selection t', 1-
There was no one in town that had both fast response speed and gas-sensitive characteristics.

This invention was made to solve the above problem, and is a gas-sensitive humidity sensor that selectively detects O, -100% relative humidity, malodorous gas, and alcohol gas concentration with a single integrated element. The element is 47,1. The purpose is to provide

This invention detects humidity using an apatite ceramic material, and detects odor gas and alcohol gas using a metal oxide between separated electrodes installed on an element substrate made of the apatite ceramic material.

In addition, the separation electrode is formed by baking ruthenium oxide.
This helps increase gas sensitivity.

The electrical resistance of the gas-sensitive and humidity-sensitive element of the present invention changes greatly at relative humidity Q of -100%, malodorous gas concentration of 0 and -1000 ppm, or alcohol gas concentration of 3000 ppm. By measuring, relative humidity, malodorous gas, and alcohol gas can be easily detected.

The details of this invention will be explained below with reference to Examples.0 Example 1 Hydroxyl anodite powder in which 10% of Ca was substituted with QNa Total size of 4 x 4 cities, thickness of 0°8 , 350k (1
It is molded at a pressure of 7c1J and fired in air at 1100°C for 6 hours. This was polished to a thickness of 250 μm, and separate electrodes (21, (31 (first and third electrodes)) made of RuO2 paste were attached as shown in the sintered body (1) in Fig. 1, and second electrodes were attached to the back side. As shown in the figure, screen print an electrode (4) (second N pole) with RuO2 paste coated on the entire surface. Next, screen print titanium oxide TlO2 paste between the separated electrodes (21, (31) at 250μ intervals. Do.Tl
O2 paste is made by pulverizing reagent-grade powder that is fired at 1000°C for 1 hour in the air.

Made by passing through a 400 mesh sieve and adding butyl calpitol. Lead wires after TiO2r printing (6), (71,
Attach +81 and bake at 800℃ for 10 minutes. The electrode formed in the above manner becomes a porous surface electrode, and humidity easily reaches the sintered body through the entire N electrode. (The element substrate 11 is made of a hydroxyapatite moisture-sensitive ceramic material.

(5) It is a keT-02 gas-sensitive material. When detecting gas, it is necessary to maintain the element at 200° C. or higher. Therefore, a Kanthal wire coil heater should be installed in place of one of the elements shown in Figs. 1 and 2, or the solid 14s and t) shown in Fig. 2 should be replaced.
Attach 2 lead wires to the 02 frost pole.

Heater and humidity sensing? It may also serve as the lt pole.

Using the gas- and humidity-sensitive element manufactured as described above, the u111 determination shown in FIG. 3H and FIG. 5 is carried out.

FIG. 3 shows the moisture sensitivity characteristics at 25°C. Measurements were made using electrode +21. +31 and connect l between this and electrode (4).
The test was carried out by applying a sine wave of V, 50H2. Electrode [21
, (31k may be applied between one electrode and electrode (4) without contact, but the measured resistance will increase.

As shown in the figure, the relative humidity is 0. At -100%, the electrical resistance changes by more than four orders of magnitude, which is extremely high. Even if it was left in a small laboratory for 6 months with or without 1V current, the percentage change was within the estimated error and it was very stable. The first feature is that other ceramic humidity sensors do not have. Also, the response is 2
- Fast at 15 seconds.

FIG. 4 shows the sensitivity characteristics when changing the element temperature. Resistance between electrodes (2+, (31) (f- measure.0l)
ii Oppm of CH3SH in the atmosphere, YuC at 021
1001]pm of H3SH. .

As shown in the figure, the resistance value changes by more than two orders of magnitude.

Figure 5 shows 0H3SI (, 1i2S, ethanol (02
H50H).

Hydrogen (H2), -carbon oxide (CO), propane (C3
I(8)% Sensitivity S to 100 ppm○
Resistance value in the atmosphere 7z lta, gas 100pp+n
If the resistance value iRg is the sensitivity S Vi, Pa/R
g means the amount of change in resistance value. Figure 5 shows element temperature 4
The temperature is 50°C. Diagram Karyo IC, R2, Co
, Cy, ■-IB K ij shows little sensitivity.

The sensitivity to methanol, inpropyl alcohol II, etc. was almost the same as that of ethanol.3 Since apatite has a strong gas adsorption ability, it is highly likely that apatite also contributes to the high sensitivity and high selectivity.

Example 2 The first half was manufactured under the same conditions as Example 1, but the second half was different in the formation process of the sensitive gas. The paste for forming the sensitive material was prepared by adding a total of 400 mesh of reagent grade tin oxide 5NO2 powder, and then adding butylcalcitol to make a 5N02 paste. Example 1
and after screen printing in the same position.

Lead F4 (61, (71, (I'll k with ij te,
800'C-7'I O minute i is attached. At this time (1)
is aqueous apatite moisture-sensitive ceramics, (21, +31
, (41t-t RuO27111-et al'fZ b
? 3', 4iAq, (51fiSnO2 gas-sensitive material.

The measurements shown in FIGS. 6 and 7 were carried out using the gas- and moisture-sensitive element using the 5n02 sensor. 6J and 7 correspond to FIGS. 4 and 5 of the first embodiment.

In this case, the sensitivity of 011581J is about 1000 times higher.

As shown in FIG. 7, the element temperature Iw is 300°C.

Although the alcohol f1 is shown as a representative example of ethanol, it shows similar sensitivity to other alcohols such as methanol and inpropyl alcohol. Note that the third example of Example 1
The measurement results corresponding to the figure were the same in Example 2, so their description will be omitted. Example 3: The first half was manufactured under the same conditions as Example 1, but the second half of the sensitive gas The formation of rays is different. Gas sensitive paste i [u, o
Screen print soot oxide 5N02 Haste Deko f+ containing 2 kO, -50 wt % (1) in the same position as in Example 1. This paste is made by crushing the reagent PSR1O2.

After passing through a 400 mesh sieve, mix Ruo2 and add butyl calpitol. After printing, connect the lead wire (
61, (7), (attached 81k, 10 at 800'C
Separately baked.

In this case, (1) hydroxyapatite moisture-sensitive ceramics.

(21e, (31, (41tl electrode made of RuO2, +51h (day n02+ RuO2) gas-sensitive material.

The measurements shown in FIGS. 8 and 9 were carried out using a gas-sensitive moisture-sensitive element using a (Sno2+Ru02) gas-sensitive material.

Figure 8 shows (jl(38H) when the device is kept at 300°C.
This is the relationship between the gas-sensitive characteristics and the RuO2 content.

However, even if the RuO2 content is 0 wt%, RuO2 ((
Electrodes (2) and (3) as main components are provided. Measure the resistance between electrodes +21 and (31 in Figure 1.O
D is Oppm of OH, SH in the atmosphere, H is 0H3E
It is in 1100pp of IH. Does the one containing 10wt% Ru0 have about 2000 times more sensitivity? Shimesu. RuO2 is 40
-50 wt%.

The resistance value in the atmosphere is 9. Sensitivity also decreases. The sensitivity mentioned here is the ratio Ra/Rg of the resistance value Ra in the atmosphere and the resistance value Rg in 10 Oppm of ethanol.

Figure 9 is C! H3SH, H2S, C! 2H50H,
On the sensitivity day, R2, 'c3uB and CO were each 1100 pp, and the element temperature was 300° C. and the RuO2 content was 10 wt%. As you can see from the figure, 0H3SH, H2S,
All except 02H50H are Fj&m'? I don't show it. methanol. For alcohols such as inpropyl alcohol, ethanol dissolution and repulsion sensitivity is shown.

In FIG. 8, R1102: OW t% i"I # is the same as Example 2.

Note that the measurements corresponding to FIG. 3 of Example 1 and Example 3 had the same IJ determination results, so their description will be omitted.

Example 4 The first half of the paste is produced under the same conditions as in Example 1, but the second half of the paste for forming gas-sensitive material is different.

RuO2? ! "O-"50 Wt % 'jtr[f
Screen print this in the same position as in Example 1.

This paste is made by grinding, pulverizing, passing through a <aa mesh sieve, mixing with □O22, and adding butyl calpitol. After printing, lead wire (6).

(Attach 71, +81 and bake at 1100°C for 10 minutes. At this time, (1) hydroxyapatite moisture-sensitive ceramics,
(21゜(31, (41 is lightning t&i5 made of RuO2
It is a gas-sensitive material (ZnO+Ru02).

All measurements shown in FIGS. 10 and 11 were carried out using a gas-sensitive moisture-sensitive element using a (znO+Ru02) gas-sensitive material.

10 and 11 correspond to FIGS. 8 and 9 of the third embodiment. In this case, the sensitivity to 0H5SH is about 2000 because RuO2 is included as in Example 3.
The response speed at 0H3SHO-+100 ppm is extremely fast at 1 second. The element temperature in the measurement of the 10th ratio and FIG. 11 is 450°C. Alcohol is shown as ethanol, but methanol is used instead.

Other alcohols, such as isopropyl alcohol, showed a similar effect to 1.1.

Note that the measurement corresponding to FIG. 3 of Example 1 had the same measurement results in Example 4, so the description thereof will be omitted.

Example 5 The first half was manufactured under the same conditions as Example 1, but the second half was different in the formation process of the gas-sensitive material.

The paste for gas sensitive is Ru O2f O, -50w
Screen printing was performed using a magnesium ferrite paste containing t% in all the same positions as in Example 1. This paste is oxalate 110000C obtained by coprecipitation method.

After firing in the atmosphere for 1 hour, crushing, and passing through a 400 mesh sieve, RuO2'? ! - Mix and add butylcarbitolke. Ferrite thread 11 construction '17Fe1
．． 5AlO, 504. After printing, lead wire C61,
(71, (Attach 8i and bake at 800℃ for 10 minutes.

In this case, (1) is a hydroxyapatite moisture-sensitive ceramic, (
21, (3), (electrode made of 41UFu02, (5)
is (magnesium ferrite + 1 < l + 02) gas sensitive 8 (M F l'°131.5 A1 [1,504
+Ru02) Carry out the measurements shown in Figures 12 and 13 using a gas-sensitive moisture-sensitive element using 7jr) 1st
2 and 13 correspond to FIG. 4 and FIG. 5 VC of the third embodiment. The heart sensitivity of this paste to 0H4S](VIL was about 600 times that of J(containing 10 wt% u02) as in Example 3, and the response speed at c1i3saO→100 ppm was very fast at 2 seconds.

In Figure 13, the element temperature at 1lll 1 foot is 250'
It is C.

Although ethanol is shown as a representative alcohol, the sensitivity is similar to other alcohols such as methanol and isopropyl alcohol. show.

Note that the measurement corresponding to FIG. 3 of Example 1 had the same measurement results in Example 5, so the description thereof will be omitted.

Top”: 1MP, 'f゛1.5Alos04'tfdl
ll I=;/;-F, Mg11 not containing A1!゛o204 also has a similar black gold color.

Unlike the old materials of Examples 1 to 4, the resistance of magnesium ferrite increases due to adsorption of scum.

(Fig. 12) It is a P-type semiconductor. Therefore, only in this case, S='B(g/Ra).

Example 6 Example 1 and 111 and a half were manufactured under the same conditions, but the second half of the process for forming the gas-sensitive material was different. Paste for sensitive gas,
Using nimeb oxide Nb2O5 paste containing 10-50 wt% of RuO2, screen print this on the same level as in Example 1. 3. This paste TrL, reagent special grade Nb205yi
ooo℃, baked in air for 1 hour, crushed, 40
RuO2' after 0 mesh sieving! It is made by mixing f and adding butylcarpitol. -7 mark A6, attach lead wires +61, (71, (81) and bake at 800'C for 10 minutes. Now (1) H hydroxyl anode (tight moisture sensitive ceramics * (2), (31) , (41i1
Ruo, , an electrode consisting of (51U (N1) 20s
-1-RuO2) gas-sensitive material 0(Nb2O5-1-
The first AEL humidity sensing element using RuO2) gas-sensitive material.
The measurements shown in FIGS. 4 and 15 were carried out. Figure 14, 1st
FIG. 5 corresponds to FIGS. 4 and 5 of the third embodiment. In this case, the sensitivity to C115E3H is about 600 times higher than that of RuO2f 10 w t +[) as in Example 3, and the response speed at 0H3SHO→100 ppm is very fast at 1 second. The element temperature in the measurements shown in FIGS. 14 and 15 was 300°C. The alcohol shown is ethanol as a representative, but what about other alcohols such as methanol and isopropyl alcohol? 1 shows similar sensitivity.

Note that the measurement corresponding to FIG. 3 of Example 1 had the same measurement results in Example 2, so the description thereof will be omitted.

In the above examples, hydroxyl apatite) =
This is an example of apatite used in the above, but other apatites, that is, those in which the hydroxyl groups are replaced with halogens.

Apatite, in which calcium is replaced with strodium, barium, lead, etc., may be used. A gas-sensitive paste may be applied between the zero-separation electrodes using the outer surface as a separation electrode.

A first plate provided on the element substrate with a ceramic material interposed therebetween.
．． Second electrode, first! A third electrode provided on the element base 82 apart from the electrode, a metal oxide sensitive to gas provided in contact with the first electrode and the third electrode and provided between the first electrode and the third electrode. Since it is a gas-sensitive and humidity-sensitive element, it is possible to selectively detect relative humidity of 0.-100 cm, malodorous gas, and alcohol gas with high sensitivity using one integrated element.

[Brief explanation of drawings]

FIGS. 1 and 2 are perspective views showing the structure of an embodiment of the present invention, with FIG. 1 showing its front surface and FIG. 2 showing its back surface. Third
The figure is a characteristic curve diagram showing the moisture sensitive characteristics of the present invention, FIGS. 4 and 6 are characteristic curve diagrams showing the temperature dependence of the gas sensitive characteristics of each embodiment of the present invention, and FIGS. 8 and 10, respectively. , FIG. 12, and FIG. 14 μ, respectively. 11, 13, and 15 are characteristic curve diagrams showing the sensitivity to various gases in each embodiment of the present invention. In the figures, (1) is an element substrate made of moisture-sensitive ceramics. (21, (31, (41) are the first, third, and third electrodes, respectively.
This corresponds to the second electrode. (5) is a gas-sensitive material, +61,
(71, (81 digit 1) - line. Note that the same reference numerals in the figures indicate the same - or corresponding parts. Agent Makoto Kazuno - Figure 1 Figure 2 Figure 3 Figure 14r4 Figure 5) 6 Figure 250 300 350 Temperature C) Figure 8 Ruo, jq content (wf''A) Figure 9 Figure 10 Ruoz @ 1 (wt -A) Figure 11 Figure 12m Ruoi 8$t (wt-/ , ) Fig. 14 RuO2-containing + (wtγ.)

Claims (5)

[Claims] (1) An element substrate made of apatite ceramics,
A first plate provided on the element substrate with the apatite ceramic interposed therebetween. A second electrode, a 3'Fl pole separated from the first electrode and provided on the element substrate, and a first pole and a 371st!Fl pole in contact with the first and third electrodes. Gas- and moisture-sensing element with metal oxide sensitive to gas provided between electrodes (2) Metal oxide f'i The gas- and moisture-sensitive element according to claim 1, which is one of titanium oxide, niobium oxide, tin oxide, zinc oxide, and magnesium ferrite. (3) The gas- and moisture-sensitive element according to claim 1, wherein the metal oxide is a mixture of one of titanium oxide, niobium oxide, tin oxide, zinc oxide, and magnesium ferrite and ruthenium oxide. (4) The gas-sensitive and moisture-sensitive element according to any one of claims 1 to 3, wherein the electrode is a porous surface electrode. (5) First. The gas- and moisture-sensitive element according to any one of claims 1 to 4, wherein the third lightning electrode is made by completely baking ruthenium oxide onto the element substrate.