JPH1019821A - Gas sensor - Google Patents
Gas sensorInfo
- Publication number
- JPH1019821A JPH1019821A JP17771996A JP17771996A JPH1019821A JP H1019821 A JPH1019821 A JP H1019821A JP 17771996 A JP17771996 A JP 17771996A JP 17771996 A JP17771996 A JP 17771996A JP H1019821 A JPH1019821 A JP H1019821A
- Authority
- JP
- Japan
- Prior art keywords
- gas
- metal oxide
- added
- ammonia
- gas sensor
- Prior art date
- Legal status (The legal status is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the status listed.)
- Withdrawn
Links
Landscapes
- Investigating Or Analyzing Materials By The Use Of Fluid Adsorption Or Reactions (AREA)
Abstract
Description
【０００１】[0001]
【発明の属する技術分野】本発明は、アンモニア濃度等
の測定を他のガス成分の影響を受けることなく正確に行
うことができるガスセンサに関するものである。BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a gas sensor capable of accurately measuring ammonia concentration and the like without being affected by other gas components.
【０００２】[0002]
【従来の技術】従来から、ガス漏れ警報器等においてガ
スの吸脱着により抵抗値が変化する金属酸化物半導体に
電極を接続し抵抗値を測定することでガスの有無を検出
するようにしたガスセンサが利用されているが、従来の
この種のガスセンサにおいては検出可能濃度が数百ppm
以上と感度の低いものであり、特に精度の高いアンモニ
アの測定には適用できないものであった。2. Description of the Related Art Conventionally, in a gas leak alarm device or the like, an electrode is connected to a metal oxide semiconductor whose resistance value changes due to adsorption and desorption of gas, and the presence or absence of gas is detected by measuring the resistance value. However, this type of conventional gas sensor has a detectable concentration of several hundred ppm.
As described above, the sensitivity was low, and it was not applicable particularly to highly accurate measurement of ammonia.
【０００３】そこで、特開平５−８７７６０号公報に示
されるように、高精度なアンモニア測定用の金属酸化物
半導体ガスセンサとして金属酸化物にＷＯ3 を用い、Ｐ
ｔ、Ｒｕ、Ａｕ、Ａｇ、Ｒｈ、Ｐｄ等の貴金属を添加し
て検出精度を高めたものが提案されている。ところが、
このガスセンサの場合には、例えば火力発電所の煙道排
ガス中におけるアンモニア濃度等を測定しようとする
と、共存するＮＯX やＣＯX 等の他のガスの影響を受け
て半導体の抵抗値が変化してしまうため正確な測定をす
ることができないという問題点があった。[0003] Therefore, as disclosed in Japanese Patent Application Laid-Open No. 5-87760, WO 3 is used as a metal oxide as a metal oxide semiconductor gas sensor for highly accurate ammonia measurement.
A proposal has been made of adding a noble metal such as t, Ru, Au, Ag, Rh, and Pd to increase the detection accuracy. However,
In the case of this gas sensor, for example, when trying to measure the ammonia concentration or the like in the flue gas of a thermal power plant, the resistance value of the semiconductor changes due to the influence of other gases such as NO X and CO X which coexist. Therefore, there is a problem that accurate measurement cannot be performed.
【０００４】[0004]
【発明が解決しようとする課題】本発明は上記のような
従来の問題点を解決して、アンモニア濃度等の測定を他
のガス成分の影響を受けることなく正確かつ高精度に行
うことができるガスセンサを提供することを目的として
完成されたものである。SUMMARY OF THE INVENTION The present invention solves the above-mentioned conventional problems, and makes it possible to measure ammonia concentration and the like accurately and accurately without being affected by other gas components. It has been completed for the purpose of providing a gas sensor.
【０００５】[0005]
【課題を解決するための手段】上記の課題を解決するた
めになされた本発明のガスセンサは、主体となる金属酸
化物に添加物を加えた金属酸化物半導体に対するガスの
吸脱着による抵抗値の変化を利用したアンモニア測定用
のガスセンサであって、前記主体となる金属酸化物をＷ
Ｏ3 とし、添加物をＭｏＯ3 としたことを特徴とするも
のである。Means for Solving the Problems A gas sensor according to the present invention which has been made to solve the above-mentioned problems has a resistance value by adsorption and desorption of gas to a metal oxide semiconductor in which an additive is added to a main metal oxide. A gas sensor for measuring ammonia using change, wherein the main metal oxide is W
O 3 and MoO 3 as an additive.
【０００６】[0006]
【発明の実施の形態】以下に、図面を参照しつつ本発明
の好ましい実施の形態を示す。図１は本発明に係るガス
センサの一例を示すもので、１は筒状のアルミナ管、２
は該アルミナ管１上に一対のＰｔ線を巻回してなる電
極、３はこの電極２を包むように形成された多孔質焼結
体からなる金属酸化物半導体層である。さらに、この金
属酸化物半導体層３の製法について述べる。まず、ＷＯ
3 についてはパラタングステン酸｛（ＮＨ4 ）10Ｗ12Ｏ
41・５Ｈ2Ｏ｝を出発原料とし、これを空気中で６００
℃・５時間加熱分解する。得られた粉末をボールミル等
で２４〜３０時間湿式粉砕し、１１０℃・５時間乾燥し
てＷＯ3 粉末を得る。ＭｏＯ3 については、モリブデン
酸アンモニウム｛（ＮＨ4 ）6 Ｍｏ7 Ｏ24・４Ｈ2 Ｏ｝
を出発原料とし、これを空気中で４００℃・５時間加熱
分解する。得られた粉末をボールミル等で２４〜３０時
間湿式粉砕し、１１０℃・５時間乾燥してＭｏＯ3 粉末
を得る。これらの作業によりサブミクロンオーダーの一
次粒子径をもった微細な粒子を得ることが可能であり、
焼結時の素子の比表面積が大きくなることによって、セ
ンサとしてより高い感度を得ることができる。得られた
各粉末は所定重量比に混合され、ボールミル等で１２時
間湿式粉砕、１１０℃・５時間乾燥して原料粉末とす
る。これを蒸留水を溶媒としてペースト化し、先述の筒
状アルミナ管１と電極２を包むように塗布する。これを
空気中で６００℃・４時間焼成し、目的の金属酸化物半
導体層３を得る。なお、原料については硝酸塩、酢酸塩
等の熱分解もしくは金属アルコキシド等の加水分解等に
よって得たものでも同様の特性のセンサ素子が得られ
る。DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS Preferred embodiments of the present invention will be described below with reference to the drawings. FIG. 1 shows an example of a gas sensor according to the present invention.
Reference numeral 3 denotes an electrode formed by winding a pair of Pt wires on the alumina tube 1, and 3 denotes a metal oxide semiconductor layer made of a porous sintered body formed so as to surround the electrode 2. Further, a method of manufacturing the metal oxide semiconductor layer 3 will be described. First, WO
For 3 paratungstate {(NH 4) 10 W 12 O
The 41 · 5H 2 O} as the starting material, 600 this in the air
Decompose by heating at ℃ for 5 hours. The obtained powder is wet-pulverized by a ball mill or the like for 24 to 30 hours, and dried at 110 ° C. for 5 hours to obtain WO 3 powder. For MoO 3, ammonium molybdate {(NH 4) 6 Mo 7 O 24 · 4H 2 O}
Is decomposed by heating at 400 ° C. for 5 hours in the air. The obtained powder is wet-ground with a ball mill or the like for 24 to 30 hours and dried at 110 ° C. for 5 hours to obtain MoO 3 powder. By these operations, it is possible to obtain fine particles having a primary particle diameter of the order of submicron,
By increasing the specific surface area of the element at the time of sintering, higher sensitivity can be obtained as a sensor. The obtained powders are mixed at a predetermined weight ratio, wet-pulverized by a ball mill or the like for 12 hours, and dried at 110 ° C. for 5 hours to obtain a raw material powder. This is made into a paste using distilled water as a solvent, and is applied so as to surround the above-described cylindrical alumina tube 1 and the electrode 2. This is fired in air at 600 ° C. for 4 hours to obtain a target metal oxide semiconductor layer 3. In addition, as for the raw material, a sensor element having similar characteristics can be obtained even if the raw material is obtained by thermal decomposition of nitrate or acetate or hydrolysis of metal alkoxide or the like.
【０００７】またガスセンサとしては、図５に示される
ように、アルミナ基盤４に一対の櫛形Ａｕ電極５、５を
焼成により形成し、このＡｕ電極５、５が接続する金属
酸化物半導体６を同じく焼成によりアルミナ基盤４に形
成したものとしてもよい。更に、アルミナ等の基盤に金
属酸化物半導体を薄膜状に形成せず、ある程度の厚みの
金属酸化物半導体に直接電極を埋設したものとしてもよ
い。As a gas sensor, as shown in FIG. 5, a pair of comb-shaped Au electrodes 5 and 5 are formed on an alumina substrate 4 by firing, and a metal oxide semiconductor 6 to which the Au electrodes 5 and 5 are connected is similarly formed. It may be formed on the alumina substrate 4 by firing. Further, the metal oxide semiconductor may not be formed in a thin film shape on a substrate such as alumina, and the electrode may be directly embedded in the metal oxide semiconductor having a certain thickness.
【０００８】そして、本発明においては前記の金属酸化
物半導体層３の主体となる金属酸化物としてＷＯ3 を用
い、かつ添加物としてＭｏＯ3 を用いた点に特徴的構成
を有するものである。添加物をＭｏＯ3 としたのは従来
のＰｔやＡｕ等の貴金属を添加した時のように被検出ガ
ス中にアンモニアの他にＮＯX やＣＯX 等のガスが共存
する場合に、それらの影響を受けてアンモニアの正確な
検出できなくなるのを防止し、アンモニア濃度等の測定
を他のガス成分の影響を受けることなく正確に行うため
であり、本発明者らが種々の添加物につき実験を繰り返
した結果、ＭｏＯ3 が最適であることを見出したのであ
る。In the present invention, WO 3 is used as the main metal oxide of the metal oxide semiconductor layer 3 and MoO 3 is used as an additive. The reason why MoO 3 is used as the additive is that when gases such as NO X and CO X coexist in the detected gas, such as when adding a noble metal such as Pt or Au, as in the case of the conventional method, the effects of these are considered. In order to prevent the detection of ammonia from becoming unacceptable due to the above, and to accurately measure the ammonia concentration and the like without being affected by other gas components, the present inventors conducted experiments on various additives. As a result of repeating, MoO 3 was found to be optimal.
【０００９】なお、前記ＭｏＯ3 の添加は単純に表面へ
塗布する方法は勿論のこと、蒸着法や含浸法、更には粉
末原料の段階で混合する方法など任意の手段を採用する
ことができる。また、ＭｏＯ3 の添加量は共存する他の
ガスの影響を受けることなくアンモニアのみを正確に検
出できるよう外配で２０重量％以上の範囲とすることが
好ましい。２０重量％未満では他のガスの影響を十分に
カットすることができないからである。そして本発明に
係るガスセンサは、例えば図２に示されるように、火力
発電所のボイラー４から出る排ガスを脱硝装置５および
脱硫装置６によって脱硝・脱硫した後、煙突７より大気
中へ放出する場合の排ガス中におけるアンモニア濃度の
測定をするよう、例えば前記煙突７の手前に設置され、
使用に供されることとなる。The MoO 3 can be added by any means such as a method of simply applying it to the surface, a vapor deposition method, an impregnation method, and a method of mixing at the stage of powder raw material. The amount of MoO 3 to be added is preferably in the range of 20% by weight or more so that only ammonia can be accurately detected without being affected by other coexisting gases. If the content is less than 20% by weight, the influence of other gases cannot be sufficiently cut. The gas sensor according to the present invention is, for example, as shown in FIG. 2, when exhaust gas discharged from a boiler 4 of a thermal power plant is denitrified and desulfurized by a denitration device 5 and a desulfurization device 6 and then discharged to the atmosphere from a chimney 7. For example, installed before the chimney 7 so as to measure the ammonia concentration in the exhaust gas,
It will be used for use.
【００１０】[0010]
【実施例】金属酸化物をＷＯ3 としＭｏＯ3 の添加量が
外配で５０重量％としたガスセンサを作成して、脱硝後
における排ガスの一般的なガス濃度に基づきＯ2 が２％
の雰囲気下でＮＨ3 が１０ppm のガスに対し、表１にあ
るような各種のガスを共存させた場合のガスセンサの抵
抗値Ｒ２（Ω）を測定した。一方、アンモニア以外のガ
スを共存しないＯ2 が２％の雰囲気下でＮＨ3 が１０pp
m のガスの場合の抵抗値Ｒ１（Ω）を測定して、共存ガ
スの妨害程度の目安として抵抗比Ｒ１／Ｒ２を算出し
た。この結果、図３に示されるように、実施例のガスセ
ンサでは抵抗比がほとんど１．０に近い値でアンモニア
の測定を他のガス成分の影響を受けることなく正確に行
えるものであることが確認できた。なお、比較例として
金属酸化物をＷＯ3 としＡｕを添加したガスセンサを作
成して同様に抵抗比Ｒ１／Ｒ２を算出した結果、いずれ
も実施例に比べ、１．０から離れた値で他のガス成分の
影響を大きく受けていることが判った。また、ＭｏＯ3
の添加量と前記抵抗比との関係を調べた結果は図４に示
されるとおりであり、外配で２０重量％以上の範囲が好
ましいことが判った。EXAMPLE A gas sensor was prepared in which the metal oxide was WO 3 and the amount of MoO 3 added was 50% by weight, and O 2 was 2% based on the general gas concentration of the exhaust gas after denitration.
The resistance value R2 (Ω) of the gas sensor was measured when various gases as shown in Table 1 were allowed to coexist with a gas containing 10 ppm of NH 3 under the atmosphere described above. On the other hand, in an atmosphere of 2% O 2 which does not coexist any gas other than ammonia, NH 3 is 10 pp.
The resistance value R1 (Ω) in the case of the gas m was measured, and the resistance ratio R1 / R2 was calculated as a measure of the degree of interference of the coexisting gas. As a result, as shown in FIG. 3, it was confirmed that in the gas sensor of the example, the measurement of ammonia could be performed accurately at a resistance ratio almost equal to 1.0 without being affected by other gas components. did it. As a comparative example, a gas sensor was prepared in which the metal oxide was WO 3 and Au was added, and the resistance ratio R1 / R2 was calculated in the same manner. It turned out that it was greatly influenced by gas components. Also, MoO 3
The result of examining the relationship between the amount of addition and the resistance ratio was as shown in FIG. 4, and it was found that the range of 20% by weight or more was preferable in the external distribution.
【００１１】[0011]
【表１】 [Table 1]
【００１２】[0012]
【発明の効果】以上の説明からも明らかなように、本発
明はアンモニア濃度等の測定を他のガス成分の影響を受
けることなく正確かつ高精度に行うことができるもので
あり、従って、火力発電所の煙道排ガス中におけるアン
モニア濃度等も共存するＮＯXやＣＯX 等の他のガスの
影響を受けることなく正確に測定することができるもの
である。よって本発明は従来の問題点を一掃したガスセ
ンサとして、産業の発展に寄与するところは極めて大で
ある。As is apparent from the above description, the present invention can measure ammonia concentration and the like accurately and accurately without being affected by other gas components. Ammonia concentration and the like in flue gas of a power plant can be accurately measured without being affected by other gases such as NO X and CO X which coexist. Therefore, the present invention greatly contributes to industrial development as a gas sensor that has eliminated the conventional problems.
【図１】 本発明の実施の形態を示す斜視図である。FIG. 1 is a perspective view showing an embodiment of the present invention.
【図２】 本発明に係るガスセンサを煙道排ガス中にお
けるアンモニア濃度の測定に適用した例を示す正面図で
ある。FIG. 2 is a front view showing an example in which the gas sensor according to the present invention is applied to the measurement of the concentration of ammonia in flue gas.
【図３】 本発明の実施例と比較例における各種の共存
ガスと抵抗比の関係を示すグラフである。FIG. 3 is a graph showing a relationship between various coexisting gases and a resistance ratio in Examples of the present invention and Comparative Examples.
【図４】 本発明の実施例におけるＭｏＯ3 の添加量と
抵抗比の関係を示すグラフである。FIG. 4 is a graph showing the relationship between the added amount of MoO 3 and the resistance ratio in the example of the present invention.
【図５】 その他の実施の形態を示す斜視図である。FIG. 5 is a perspective view showing another embodiment.
１ アルミナ管 ２ 電極 ３ 金属酸化物半導体層 Reference Signs List 1 alumina tube 2 electrode 3 metal oxide semiconductor layer
フロントページの続き (72)発明者 山添 昇 福岡県春日市松ケ丘４丁目32番地 (72)発明者 三浦 則雄 福岡県福岡市中央区平尾３−17−５−301 (72)発明者 松田 和幸 愛知県名古屋市瑞穂区須田町２番56号 日 本碍子株式会社内 (72)発明者 菱木 達也 愛知県名古屋市瑞穂区須田町２番56号 日 本碍子株式会社内Continued on the front page (72) Inventor Noboru Yamazoe 4-32 Matsugaoka, Kasuga City, Fukuoka Prefecture (72) Inventor Norio Miura 3-17-5-301 Hirao, Chuo-ku, Fukuoka City, Fukuoka Prefecture (72) Inventor Kazuyuki Matsuda Aichi Prefecture (56) Inventor Tatsuya Hishigi, Japan 2-56, Suda-cho, Mizuho-ku, Nagoya-shi, Aichi Japan
Claims (3)
金属酸化物半導体に対するガスの吸脱着による抵抗値の
変化を利用したアンモニア測定用のガスセンサであっ
て、前記主体となる金属酸化物をＷＯ3 とし、添加物を
ＭｏＯ3 としたことを特徴とするガスセンサ。1. A gas sensor for measuring ammonia using a change in resistance value due to adsorption and desorption of a gas to and from a metal oxide semiconductor obtained by adding an additive to a main metal oxide, wherein the main metal oxide is Is WO 3 and the additive is MoO 3 .
上である請求項１に記載のガスセンサ。2. The gas sensor according to claim 1, wherein the amount of MoO 3 added is 20% by weight or more as an external component.
ある請求項１に記載のガスセンサ。 3. The gas sensor according to claim 1, wherein the amount of MoO 3 added is 50% by weight as an external component.
Priority Applications (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| JP17771996A JPH1019821A (en) | 1996-07-08 | 1996-07-08 | Gas sensor |
Applications Claiming Priority (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| JP17771996A JPH1019821A (en) | 1996-07-08 | 1996-07-08 | Gas sensor |
Publications (1)
| Publication Number | Publication Date |
|---|---|
| JPH1019821A true JPH1019821A (en) | 1998-01-23 |
Family
ID=16035921
Family Applications (1)
| Application Number | Title | Priority Date | Filing Date |
|---|---|---|---|
| JP17771996A Withdrawn JPH1019821A (en) | 1996-07-08 | 1996-07-08 | Gas sensor |
Country Status (1)
| Country | Link |
|---|---|
| JP (1) | JPH1019821A (en) |
Cited By (2)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| US7341694B2 (en) | 2002-09-25 | 2008-03-11 | Ngk Spark Plug Co., Ltd. | Ammonia sensor |
| CN110879238A (en) * | 2019-10-25 | 2020-03-13 | 东北大学 | Molybdenum trioxide nano-structure sensitive material, corresponding ammonia gas sensor and preparation method |
-
1996
- 1996-07-08 JP JP17771996A patent/JPH1019821A/en not_active Withdrawn
Cited By (3)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| US7341694B2 (en) | 2002-09-25 | 2008-03-11 | Ngk Spark Plug Co., Ltd. | Ammonia sensor |
| CN110879238A (en) * | 2019-10-25 | 2020-03-13 | 东北大学 | Molybdenum trioxide nano-structure sensitive material, corresponding ammonia gas sensor and preparation method |
| CN110879238B (en) * | 2019-10-25 | 2021-08-24 | 东北大学 | Molybdenum trioxide nano-structure sensitive material, corresponding ammonia gas sensor and preparation method |
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Legal Events
| Date | Code | Title | Description |
|---|---|---|---|
| A300 | Withdrawal of application because of no request for examination |
Free format text: JAPANESE INTERMEDIATE CODE: A300 Effective date: 20031007 |