JPS6222414B2 - - Google Patents
Info
- Publication number
- JPS6222414B2 JPS6222414B2 JP57170125A JP17012582A JPS6222414B2 JP S6222414 B2 JPS6222414 B2 JP S6222414B2 JP 57170125 A JP57170125 A JP 57170125A JP 17012582 A JP17012582 A JP 17012582A JP S6222414 B2 JPS6222414 B2 JP S6222414B2
- Authority
- JP
- Japan
- Prior art keywords
- gas
- sulfate ions
- oxide
- additives
- sensitivity
- 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.)
- Expired
Links
- QAOWNCQODCNURD-UHFFFAOYSA-L Sulfate Chemical compound [O-]S([O-])(=O)=O QAOWNCQODCNURD-UHFFFAOYSA-L 0.000 claims description 20
- 239000000654 additive Substances 0.000 claims description 13
- 238000001514 detection method Methods 0.000 claims description 10
- 239000010936 titanium Substances 0.000 claims description 10
- 239000000463 material Substances 0.000 claims description 9
- 229910006404 SnO 2 Inorganic materials 0.000 claims description 3
- 229910052719 titanium Inorganic materials 0.000 claims description 3
- FYYHWMGAXLPEAU-UHFFFAOYSA-N Magnesium Chemical compound [Mg] FYYHWMGAXLPEAU-UHFFFAOYSA-N 0.000 claims description 2
- 229910010413 TiO 2 Inorganic materials 0.000 claims description 2
- 229910052749 magnesium Inorganic materials 0.000 claims description 2
- 239000011777 magnesium Substances 0.000 claims description 2
- 229910000859 α-Fe Inorganic materials 0.000 claims description 2
- 238000010304 firing Methods 0.000 claims 2
- ATJFFYVFTNAWJD-UHFFFAOYSA-N Tin Chemical compound [Sn] ATJFFYVFTNAWJD-UHFFFAOYSA-N 0.000 claims 1
- RTAQQCXQSZGOHL-UHFFFAOYSA-N Titanium Chemical compound [Ti] RTAQQCXQSZGOHL-UHFFFAOYSA-N 0.000 claims 1
- 238000000465 moulding Methods 0.000 claims 1
- VSZWPYCFIRKVQL-UHFFFAOYSA-N selanylidenegallium;selenium Chemical compound [Se].[Se]=[Ga].[Se]=[Ga] VSZWPYCFIRKVQL-UHFFFAOYSA-N 0.000 claims 1
- 239000007789 gas Substances 0.000 description 62
- VNWKTOKETHGBQD-UHFFFAOYSA-N methane Chemical group C VNWKTOKETHGBQD-UHFFFAOYSA-N 0.000 description 30
- 230000035945 sensitivity Effects 0.000 description 22
- 230000000694 effects Effects 0.000 description 12
- ATUOYWHBWRKTHZ-UHFFFAOYSA-N Propane Chemical compound CCC ATUOYWHBWRKTHZ-UHFFFAOYSA-N 0.000 description 10
- 239000000203 mixture Substances 0.000 description 9
- 229910052718 tin Inorganic materials 0.000 description 8
- 229910052726 zirconium Inorganic materials 0.000 description 8
- 239000003153 chemical reaction reagent Substances 0.000 description 7
- 239000003054 catalyst Substances 0.000 description 6
- 239000001294 propane Substances 0.000 description 5
- 239000000758 substrate Substances 0.000 description 5
- 239000000843 powder Substances 0.000 description 4
- PNEYBMLMFCGWSK-UHFFFAOYSA-N aluminium oxide Inorganic materials [O-2].[O-2].[O-2].[Al+3].[Al+3] PNEYBMLMFCGWSK-UHFFFAOYSA-N 0.000 description 3
- 239000010931 gold Substances 0.000 description 3
- 239000001257 hydrogen Substances 0.000 description 3
- 229910052739 hydrogen Inorganic materials 0.000 description 3
- UQSXHKLRYXJYBZ-UHFFFAOYSA-N iron oxide Inorganic materials [Fe]=O UQSXHKLRYXJYBZ-UHFFFAOYSA-N 0.000 description 3
- 239000003949 liquefied natural gas Substances 0.000 description 3
- 229910044991 metal oxide Inorganic materials 0.000 description 3
- 150000004706 metal oxides Chemical class 0.000 description 3
- NDLPOXTZKUMGOV-UHFFFAOYSA-N oxo(oxoferriooxy)iron hydrate Chemical compound O.O=[Fe]O[Fe]=O NDLPOXTZKUMGOV-UHFFFAOYSA-N 0.000 description 3
- XOLBLPGZBRYERU-UHFFFAOYSA-N tin dioxide Chemical compound O=[Sn]=O XOLBLPGZBRYERU-UHFFFAOYSA-N 0.000 description 3
- GWEVSGVZZGPLCZ-UHFFFAOYSA-N Titan oxide Chemical compound O=[Ti]=O GWEVSGVZZGPLCZ-UHFFFAOYSA-N 0.000 description 2
- 238000002441 X-ray diffraction Methods 0.000 description 2
- 238000000862 absorption spectrum Methods 0.000 description 2
- 230000000996 additive effect Effects 0.000 description 2
- 230000000052 comparative effect Effects 0.000 description 2
- 238000010586 diagram Methods 0.000 description 2
- 238000004880 explosion Methods 0.000 description 2
- 239000002360 explosive Substances 0.000 description 2
- PCHJSUWPFVWCPO-UHFFFAOYSA-N gold Chemical compound [Au] PCHJSUWPFVWCPO-UHFFFAOYSA-N 0.000 description 2
- 229910052737 gold Inorganic materials 0.000 description 2
- 238000010438 heat treatment Methods 0.000 description 2
- 150000002431 hydrogen Chemical class 0.000 description 2
- RUTXIHLAWFEWGM-UHFFFAOYSA-H iron(3+) sulfate Chemical compound [Fe+3].[Fe+3].[O-]S([O-])(=O)=O.[O-]S([O-])(=O)=O.[O-]S([O-])(=O)=O RUTXIHLAWFEWGM-UHFFFAOYSA-H 0.000 description 2
- 229910000360 iron(III) sulfate Inorganic materials 0.000 description 2
- NNPPMTNAJDCUHE-UHFFFAOYSA-N isobutane Chemical compound CC(C)C NNPPMTNAJDCUHE-UHFFFAOYSA-N 0.000 description 2
- CPLXHLVBOLITMK-UHFFFAOYSA-N magnesium oxide Inorganic materials [Mg]=O CPLXHLVBOLITMK-UHFFFAOYSA-N 0.000 description 2
- 239000000395 magnesium oxide Substances 0.000 description 2
- AXZKOIWUVFPNLO-UHFFFAOYSA-N magnesium;oxygen(2-) Chemical compound [O-2].[Mg+2] AXZKOIWUVFPNLO-UHFFFAOYSA-N 0.000 description 2
- 239000011812 mixed powder Substances 0.000 description 2
- RVTZCBVAJQQJTK-UHFFFAOYSA-N oxygen(2-);zirconium(4+) Chemical compound [O-2].[O-2].[Zr+4] RVTZCBVAJQQJTK-UHFFFAOYSA-N 0.000 description 2
- BASFCYQUMIYNBI-UHFFFAOYSA-N platinum Chemical compound [Pt] BASFCYQUMIYNBI-UHFFFAOYSA-N 0.000 description 2
- 231100000572 poisoning Toxicity 0.000 description 2
- 230000000607 poisoning effect Effects 0.000 description 2
- 239000010970 precious metal Substances 0.000 description 2
- 239000007858 starting material Substances 0.000 description 2
- 229910001928 zirconium oxide Inorganic materials 0.000 description 2
- OTMSDBZUPAUEDD-UHFFFAOYSA-N Ethane Chemical compound CC OTMSDBZUPAUEDD-UHFFFAOYSA-N 0.000 description 1
- LFQSCWFLJHTTHZ-UHFFFAOYSA-N Ethanol Chemical compound CCO LFQSCWFLJHTTHZ-UHFFFAOYSA-N 0.000 description 1
- UFHFLCQGNIYNRP-UHFFFAOYSA-N Hydrogen Chemical compound [H][H] UFHFLCQGNIYNRP-UHFFFAOYSA-N 0.000 description 1
- GSEJCLTVZPLZKY-UHFFFAOYSA-N Triethanolamine Chemical compound OCCN(CCO)CCO GSEJCLTVZPLZKY-UHFFFAOYSA-N 0.000 description 1
- 239000000853 adhesive Substances 0.000 description 1
- 230000001070 adhesive effect Effects 0.000 description 1
- 230000032683 aging Effects 0.000 description 1
- 238000007605 air drying Methods 0.000 description 1
- 150000001450 anions Chemical class 0.000 description 1
- 229910001566 austenite Inorganic materials 0.000 description 1
- 239000011230 binding agent Substances 0.000 description 1
- 239000002131 composite material Substances 0.000 description 1
- 230000006378 damage Effects 0.000 description 1
- 230000005484 gravity Effects 0.000 description 1
- 239000001282 iso-butane Substances 0.000 description 1
- 238000004519 manufacturing process Methods 0.000 description 1
- 239000012528 membrane Substances 0.000 description 1
- 238000000034 method Methods 0.000 description 1
- 239000003345 natural gas Substances 0.000 description 1
- 229910000510 noble metal Inorganic materials 0.000 description 1
- 239000002245 particle Substances 0.000 description 1
- 229910052697 platinum Inorganic materials 0.000 description 1
- 238000012827 research and development Methods 0.000 description 1
- 229910001925 ruthenium oxide Inorganic materials 0.000 description 1
- WOCIAKWEIIZHES-UHFFFAOYSA-N ruthenium(iv) oxide Chemical compound O=[Ru]=O WOCIAKWEIIZHES-UHFFFAOYSA-N 0.000 description 1
- 239000004065 semiconductor Substances 0.000 description 1
- 239000011540 sensing material Substances 0.000 description 1
- 238000001179 sorption measurement Methods 0.000 description 1
- 229910001220 stainless steel Inorganic materials 0.000 description 1
- 239000010935 stainless steel Substances 0.000 description 1
- 239000000126 substance Substances 0.000 description 1
- 229910001887 tin oxide Inorganic materials 0.000 description 1
- 239000002341 toxic gas Substances 0.000 description 1
Classifications
-
- G—PHYSICS
- G01—MEASURING; TESTING
- G01N—INVESTIGATING OR ANALYSING MATERIALS BY DETERMINING THEIR CHEMICAL OR PHYSICAL PROPERTIES
- G01N27/00—Investigating or analysing materials by the use of electric, electrochemical, or magnetic means
- G01N27/02—Investigating or analysing materials by the use of electric, electrochemical, or magnetic means by investigating impedance
- G01N27/04—Investigating or analysing materials by the use of electric, electrochemical, or magnetic means by investigating impedance by investigating resistance
- G01N27/12—Investigating or analysing materials by the use of electric, electrochemical, or magnetic means by investigating impedance by investigating resistance of a solid body in dependence upon absorption of a fluid; of a solid body in dependence upon reaction with a fluid, for detecting components in the fluid
Landscapes
- Chemical & Material Sciences (AREA)
- Chemical Kinetics & Catalysis (AREA)
- Electrochemistry (AREA)
- Physics & Mathematics (AREA)
- Health & Medical Sciences (AREA)
- Life Sciences & Earth Sciences (AREA)
- Analytical Chemistry (AREA)
- Biochemistry (AREA)
- General Health & Medical Sciences (AREA)
- General Physics & Mathematics (AREA)
- Immunology (AREA)
- Pathology (AREA)
- Investigating Or Analyzing Materials By The Use Of Fluid Adsorption Or Reactions (AREA)
Description
産業上の利用分野
本発明は可燃性ガスの検知に使用する複合金属
酸化物半導体を用いたガス検知素子に関するもの
である。
従来例の構成とその問題点
近年、可燃性ガスの検知素子材料について種々
の研究開発が活発化してきている。これは、一般
家庭を中心に各種工場などで可燃性ガスによる爆
発事故や有毒ガスによる中毒事故が多発し、大き
な社会問題となつていることに強く起因してい
る。
特にプロパンガスは、爆発下限界（LEL）が
低く、かつ比重が空気よりも大きく、部屋に停滞
しやすいために事故があとを断たず、毎年多数の
死傷者を出している。
近年になつて、酸化第二錫（SnO2）やガンマ型
酸化第二鉄（γ−Fe2O3）などの金属酸化物を用
いたガス検知素子が実用化され、ガス漏れ警報器
などに応用されている。そして、ガス漏れなどの
事態が発生してもLELに至るまでの間に、プロ
パンガスの存在をいち早く検知し、爆発を未然に
防げるようになつている。
ところで、日本でもメタンガスを主成分とする
液化天然ガス（LNG）が一般家庭用として用い
られるようになり、徐々に普及して来ている。し
たがつて、このLNGの主成分であるメタンガス
を感度よく検出するガス検知素子の要請も非常に
大きくなつてきている。
勿論、すでにメタンガスに感応するガス検知素
子は開発されてはいるが、その多くは感応体材料
に増感剤として貫金属触媒を用いているため、
種々のガスによる触媒被毒の問題、メタンガスに
対する感度が小さい点、あるいは特性の経時変化
が大きい点などの課題を抱えている。
例えば、メタンガスはそれ自身非常に安定なガ
スであるだけに、これに十分な感度を有する検知
素子は非常に高活性である必要があるが、従来は
メタンガスに対して大きな感度を実現するため
に、貴金属触媒を感応体材料に添加して用いる
か、あるいは感応体を例えば450℃以上のかなり
高い温度で動作させるなどの工夫がなされてき
た。しかしながら、実用に際して未だ不十分な特
性であるのが現状である。
発明の目的
本発明はこのような状況に鑑みてなされたもの
で、貴金属触媒を一切添加することなく、また
400℃と比較的低い動作温度でも対メタン感度の
大きいガス検知素子を実現するものである。
発明の構成
本発明はマグネシウムフエライト
（MgFe2O4）をガス感応体として用いたガス検知
素子において、これに含まれる種々の陰イオンの
ガス感応特性に及ぼす影響ならびに添加物の効果
について検討している中で見い出されたものであ
る。
すなわち本発明のガス検知素子は、硫酸イオン
が0.005〜10重量％含有されたMgFe2O4に、添加
物としてSn、ZrおよびTiのうち少なくともひと
つが、それぞれSnO2、ZrO2およびTiO2に換算し
て添加物総量で0.1〜50モル％含むものをガス感
応体として用いたものであり、これはガス感応体
の母材料である硫酸イオンを含有するMgFe2O4
にSn、ZrあるいはTiと添加することにより、ガ
ス感応特性とその信頼性が飛躍的に向上し、しか
も先述のメタンガスに対しても実用上十分大きな
感度を実現し得ることを見出したことによつてな
されたものである。
実施例の説明
以下に本発明の実施例を説明する。まず実施例
１においては、MgFe2O4に含有される硫酸イオ
ンの量を一定にし、添加物であるSn、Zrあるい
はTiの添加量ならびにそれらの組み合わせを変
えた場合について述べることにする。
実施例 １
酸化マグネシウム（MgO）の市販試薬を20
ｇ、酸化第二鉄（Fe2O3）の市販試薬を80ｇそれ
ぞれ秤取し、これをステンレススチール製のポツ
トで５時間湿式混合した。この混合物を乾燥、粉
砕し、然る後に1300℃の温度で２時間熱処理し
た。これを再度粉砕し、これに硫酸イオンを含有
させるため添加物として、硫酸第二鉄（Fe2
（SO4）3-xH2O）試薬を25ｇ添加し、らいかい機で
２時間混合した。これらの混合物をいくつかに等
分割し、これにそれぞれ市販の酸化第二錫
（SnO2）、酸化ジルコニウム（ZrO2）および酸化チ
タン（TiO2）試薬を、単独あるいは複数の組み合
わせで添加した。そしてそれぞれの粉体をさらに
らいかい機で３時間乾式混合した。そしてこれら
にそれぞれ有機バインダーを加えて100〜200μの
大きさの粒子に整粒した。次にこれらの粉体を直
方体形状に加圧成型し、空気中で600℃の温度で
１時間焼成した。次にこの焼結体の表面にAuを
蒸着して一対の櫛形電極を形成し、その裏面には
白金発熱体を無機接着剤で貼りつけてヒータとし
検知素子を作製した。この発熱体に電流を通じ、
その電流値を調節して素子の動作温度を制御し
た。素体温度を400℃に保持して、そのガス感応
特性を測定した。
空気中における抵抗値（Ra）については、乾
燥した空気が乱流のできない程度にゆつくり撹拌
されている容積50の測定容器中で測定し、ガス
中での抵抗値（Rg）はこの容器の中に純度99％
以上のメタン（CH4）及び水素（H2）の各ガスを容
量比率にして10ppm／秒の割合で流入させ、そ
の濃度が0.2容量％に達した時にそれぞれ測定し
た。測定するガス濃度を0.2％に選んだのは、ガ
ス検知素子として実用上要望される検知濃度がそ
のガスの爆発下限界濃度（LEL）の数10分の１
から数分の１の範囲であり、上記のガスのそれぞ
れのLELが約２容量％から５容量％であるから
である。
またガス感応体に含まれる硫酸イオン
（SO4 --）の存在は赤外線吸収スペクトルで確認
し、含有されている量はTG−DTA曲線及び螢光
Ｘ線分析から同定した。その結果、これらの焼結
感応体に含まれている硫酸イオンの量は0.14〜
0.18重量％であつた。
第１図〜第３図に、添加物をそれぞれ単独で添
加した場合のガス感応特性の添加量依存性を示
す。感応特性は、(i)ガス感度（Ra／Rg）、(ii)抵抗
経時変化率△Ｒ（感応体を400℃の温度で2000時
間保持した場合の抵抗値の初期値に対する変化
率）で評価した。また第１表には、添加物を組み
合わせて用いた場合のやはりガス感度（Ra／
Rg）と、抵抗経時変化率（△Ｒ）を示す。なお
△Ｒは表中の（ ）内に記載した。
第１図〜第３図、および第１表から明らかなよ
うに、Sn、ZrあるいはTiを単独ないしは組み合
わせて添加することにより、ガス感応特性（ガス
感度：Ra／Rg）が大きく向上している。また注
目すべきは抵抗値の経時変化であり、これらの添
加物を加えることによりその変化率が大巾に減少
している。このようにSn、ZrあるいはTiの添加
によりガス感応特性と信頼性の飛躍的な向上が実
現できることがわかる。
本発明において添加物総量を0.1〜50モル％に
限定したのは、0.1モル％未満では、第１図〜第
３図および第１表に見られるように、ガス感応特
性ならびに信頼性を向上せしめる効果が見られ
ず、逆に50モル％を超えると抵抗値自身が高くな
り、また特性の安定性に欠けるからである。表中
で＊印を付したものがこれらに該当するものであ
り、第１表の中では比較例として記載しておい
た。
INDUSTRIAL APPLICATION FIELD The present invention relates to a gas detection element using a composite metal oxide semiconductor used to detect combustible gas. Conventional configuration and its problems In recent years, various research and development activities have become active regarding materials for sensing elements for flammable gases. This is strongly attributable to the fact that explosion accidents caused by flammable gases and poisoning accidents caused by toxic gases occur frequently, mainly in households and in various factories, and have become a major social problem. Propane gas, in particular, has a low explosive limit (LEL) and a higher specific gravity than air, so it easily stagnates in rooms, resulting in numerous accidents and injuries every year. In recent years, gas detection elements using metal oxides such as stannic oxide (SnO 2 ) and gamma-type ferric oxide (γ-Fe 2 O 3 ) have been put into practical use, and are used in gas leak alarms, etc. It is applied. Even in the event of a gas leak, the presence of propane gas can be quickly detected before reaching the LEL, making it possible to prevent an explosion. Incidentally, in Japan, liquefied natural gas (LNG), whose main component is methane gas, has come to be used for general household use and is gradually becoming popular. Therefore, the demand for gas detection elements that can sensitively detect methane gas, which is the main component of LNG, is increasing. Of course, gas detection elements sensitive to methane gas have already been developed, but most of them use transmetallic catalysts as sensitizers in the sensitizer material.
Problems include catalyst poisoning by various gases, low sensitivity to methane gas, and large changes in characteristics over time. For example, since methane gas itself is a very stable gas, a sensing element with sufficient sensitivity must be extremely active. Efforts have been made to use a noble metal catalyst added to the susceptor material, or to operate the susceptor at a considerably high temperature, for example, 450° C. or higher. However, the current situation is that the properties are still insufficient for practical use. Purpose of the Invention The present invention was made in view of the above situation, and it is possible to produce a catalyst without adding any precious metal catalyst.
The goal is to realize a gas detection element with high sensitivity to methane even at a relatively low operating temperature of 400°C. Structure of the Invention The present invention is a gas sensing element using magnesium ferrite (MgFe 2 O 4 ) as a gas sensing material, and the effects of various anions contained therein on the gas sensitivity characteristics and the effects of additives were investigated. It was discovered in the middle of the day. That is, the gas sensing element of the present invention is made of MgFe 2 O 4 containing 0.005 to 10% by weight of sulfate ions, and at least one of Sn, Zr and Ti as additives to SnO 2 , ZrO 2 and TiO 2 , respectively. A substance containing 0.1 to 50 mol% of additives in terms of the total amount was used as a gas sensitive material, and this is MgFe 2 O 4 containing sulfate ions, which is the base material of the gas sensitive material.
We discovered that by adding Sn, Zr, or Ti to the gas, the gas sensitivity characteristics and its reliability can be dramatically improved, and it is also possible to achieve a sensitivity that is sufficiently large for practical use even to the aforementioned methane gas. It was a gift. Description of Examples Examples of the present invention will be described below. First, in Example 1, a case will be described in which the amount of sulfate ions contained in MgFe 2 O 4 is kept constant, and the amounts of additives Sn, Zr, or Ti and their combinations are varied. Example 1 A commercially available reagent of magnesium oxide (MgO)
80 g of commercially available reagents of ferric oxide (Fe 2 O 3 ) and ferric oxide (Fe 2 O 3 ) were weighed out and wet-mixed in a stainless steel pot for 5 hours. This mixture was dried, ground and then heat treated at a temperature of 1300°C for 2 hours. This is ground again and ferric sulfate (Fe 2
25g of (SO 4 ) 3-x H 2 O) reagent was added and mixed for 2 hours using a sieve. These mixtures were equally divided into several parts, and commercially available reagents of stannic oxide (SnO 2 ), zirconium oxide (ZrO 2 ), and titanium oxide (TiO 2 ) were added thereto, either singly or in combination. Then, each powder was further dry-mixed for 3 hours using a miller. Then, an organic binder was added to each of these to form particles with a size of 100 to 200μ. Next, these powders were pressure-molded into a rectangular parallelepiped shape and fired in air at a temperature of 600°C for 1 hour. Next, Au was vapor-deposited on the surface of this sintered body to form a pair of comb-shaped electrodes, and a platinum heating element was attached to the back surface with an inorganic adhesive to serve as a heater and a sensing element was fabricated. Passing current through this heating element,
The operating temperature of the device was controlled by adjusting the current value. The element temperature was maintained at 400°C and its gas sensitivity characteristics were measured. The resistance value (Ra) in air was measured in a measuring container with a volume of 50 mm in which dry air was stirred slowly to the extent that no turbulence occurred, and the resistance value (Rg) in gas was determined by 99% purity inside
The above methane (CH 4 ) and hydrogen (H 2 ) gases were made to flow at a volume ratio of 10 ppm/sec, and each was measured when the concentration reached 0.2 volume %. The gas concentration to be measured was chosen to be 0.2% because the practically required detection concentration for a gas detection element is several tenths of the lower explosive limit concentration (LEL) of the gas.
This is because the LEL of each of the above gases is approximately 2% by volume to 5% by volume. Further, the presence of sulfate ions (SO 4 -- ) contained in the gas sensitive material was confirmed by infrared absorption spectrum, and the amount contained was identified from the TG-DTA curve and fluorescent X-ray analysis. As a result, the amount of sulfate ions contained in these sintered sensitizers ranges from 0.14 to
It was 0.18% by weight. FIGS. 1 to 3 show the dependence of the gas sensitivity characteristics on the amount added when each additive is added individually. Sensitive characteristics are evaluated by (i) gas sensitivity (Ra/Rg), (ii) rate of change in resistance over time △R (rate of change in resistance value from the initial value when the sensitive body is held at a temperature of 400°C for 2000 hours) did. Table 1 also shows the gas sensitivity (Ra/
Rg) and resistance change rate over time (ΔR). Note that ΔR is written in parentheses in the table. As is clear from Figures 1 to 3 and Table 1, the gas sensitivity characteristics (gas sensitivity: Ra/Rg) are greatly improved by adding Sn, Zr, or Ti singly or in combination. . Also noteworthy is the change in resistance value over time, and the addition of these additives significantly reduces the rate of change. It can thus be seen that the addition of Sn, Zr, or Ti can dramatically improve gas sensitivity characteristics and reliability. The reason why the total amount of additives is limited to 0.1 to 50 mol% in the present invention is that less than 0.1 mol% improves gas sensitivity characteristics and reliability, as shown in Figures 1 to 3 and Table 1. This is because no effect is observed, and on the contrary, if it exceeds 50 mol%, the resistance value itself becomes high and the stability of the characteristics is lacking. Those marked with * in the table correspond to these, and are listed as comparative examples in Table 1.
【表】
＊ 比較例
ところで、一般的に感応体はある程度非晶質の
状態の金属酸化物の方が、結晶化されているもの
より可燃性ガスに対する吸着現象などの物理化学
現象が活性になり易いと云われている。しかし、
ほぼ完全に近く結晶化されている市販試薬を用い
て作成されたMgFe2O4でも、硫酸イオンを含有
せしめ、さらにSn、ZrあるいはTiを添加するこ
とにより極めて高い活性度を示し、しかもこれが
経時的に安定なため、結果的に非常に大きなガス
感度と高い信頼性を実現し得ることがわかる。
この実施例１では、感応体が焼結体の場合であ
り、含有される硫酸イオン量が一定で、そして添
加物の量、組み合わせが異る場合について述べ
た。次に示す実施例２では感応体が焼結膜の場合
で、実施例１とは逆に添加物の種類と量を一定に
して含有される硫酸イオンの量を変えた場合につ
いて述べる。すなわち実施例２では、本発明が感
応体を焼結膜とした場合でも有効であることを確
認し、また含有される硫酸イオン量がガス感応特
性に対してどのような効果を持つかについて述べ
ることにする。
実施例 ２
実施例１と同様の方法で作成された
MgFe2O4100ｇに、やはり市販の酸化第二錫
（SnO2）、酸化ジルコニウム（ZrO2）および酸化チ
タン（TiO2）試薬を第２表に示す様な割合になる
様に秤取し、それぞれをらいかい機にて２時間混
合した。次にそれぞれの混合粉体を８等分割し、
これに予め種々の濃度に調製された硫酸第二鉄
（Fe2（SO4）3-xH2O）溶液を加え、しかる後にそ
れぞれの粉体をやはりらいかい機で１時間混合し
た。このようにして代表例としての酸化物組成の
種類が３種類（試料Ａ〜Ｃ）、硫酸イオン量の異
なるものがそれぞれの酸化物組成に対して８種
類、計24種類の試料が得られた。[Table] * Comparative example By the way, in general, metal oxides that are amorphous to some extent are more active in physicochemical phenomena such as adsorption to combustible gases than those that are crystallized. It is said to be easy. but,
Even MgFe 2 O 4 prepared using a commercially available reagent that is almost completely crystallized shows extremely high activity by containing sulfate ions and further adding Sn, Zr, or Ti. As a result, it can be seen that extremely high gas sensitivity and high reliability can be achieved. In Example 1, the sensitive body is a sintered body, the amount of sulfate ions contained is constant, and the amounts and combinations of additives are varied. In Example 2 shown below, the sensitive body is a sintered film, and contrary to Example 1, the type and amount of additives are kept constant and the amount of sulfate ions contained is varied. That is, in Example 2, it was confirmed that the present invention is effective even when the sensitive body is a sintered film, and the effect of the amount of sulfate ions contained on the gas sensitivity characteristics is described. Make it. Example 2 Created in the same manner as Example 1
To 100 g of MgFe 2 O 4 , commercially available tin oxide (SnO 2 ), zirconium oxide (ZrO 2 ), and titanium oxide (TiO 2 ) reagents were weighed out in the proportions shown in Table 2. Each was mixed for 2 hours using a sieve machine. Next, each mixed powder was divided into 8 equal parts,
Ferric sulfate (Fe 2 (SO 4 ) 3-x H 2 O) solutions prepared in advance at various concentrations were added to this, and then each powder was mixed for 1 hour using a miller. In this way, a total of 24 types of samples were obtained, including 3 types of representative oxide compositions (samples A to C) and 8 types of samples with different amounts of sulfate ions for each oxide composition. .
【表】
このようにして得られたいくつかの混合粉体を
空気中で400℃の温度で２時間熱処理した。さら
にこの粉体を50〜100μに整粒し、トリエタノー
ルアミンを加えてペースト化した。一方、ガス検
知素子の基板として縦、横それぞれ５mm、厚み
0.5mmのアルミナ基板を用意し、この表面に0.5mm
の間隔に櫛形に金ペーストを印刷し、焼きつけて
一対の櫛形電極を形成した。そして、アルミナ基
板の裏面には金電極の間に市販の酸化ルテニウム
のグレーズ抵抗体を印刷し、焼きつけてヒータと
した。
次に、上述のペーストを基板の表面に約65μの
厚みに印刷し、室温で自然乾燥させた後、400℃
の温度になるまで徐々に加熱し、この温度で１時
間保持した。この段階でペーストが蒸発し硫酸イ
オンを含有するそれぞれの酸化物組成の焼結膜に
なつた。このガス感応体の厚みは約60μであつ
た。このようにしてガス検知素子を得た。
またガス感応膜に含まれる硫酸イオン量の同定
は、上記の各ペーストの一部を、アルミナ基板に
印刷するのではなく、ペーストのまま上述と同じ
様に400℃の温度で徐加熱し、これをTG−DTA
ならびに螢光Ｘ線分析にかけて行なつた。また硫
酸イオンの存在の確認は実施例１と同じく赤外線
吸収スペクトルを分析することにより行なつた。
それぞれの検知素子のガス感応特性を実施例１
の場合と同様の方法で測定した。第４図〜第６図
に酸化物組成の異る試料Ａ〜Ｃのガス感度
（Ra／Rg）と含有される硫酸イオンとの関係をそ
れぞれ示す。また第３表には、経時特性の代表例
として、試料Ａ〜Ｃにおいて硫酸イオンが２〜５
重量％含有されているものについて実施例１と同
じ方法で評価した時の抵抗値の経時変化率を示
す。なお実施例２においては、被検ガスとしては
メタンとプロパンを用いた。
第４図〜第６図から明らかなように、感応体が
焼結膜であつても、実施例１で得られたのとほぼ
同じ特性が得られている。また第３表からも明ら
かなように、抵抗値の経時変化率も実施例１と同
様非常に小さい。
また第４図〜第６図を見ればわかるように、硫
酸イオンの量が0.005重量％未満ではSn、Zrある
いはTiの添加効果がなく本発明の効果が期待で
きない。また逆に10.0重量％を超えると特性の安
定性、あるいは機械的強度の面で実用性に欠ける
ようになる。本発明のガス検知素子で含有される
硫酸イオンの量を0.005〜10.0重量％に限定した
のは上述した理由に依る。[Table] Several mixed powders thus obtained were heat treated in air at a temperature of 400°C for 2 hours. Further, this powder was sized to a size of 50 to 100μ, and triethanolamine was added to form a paste. On the other hand, as a substrate for the gas detection element, the length and width are each 5 mm, and the thickness is
Prepare a 0.5mm alumina substrate, and place 0.5mm on this surface.
A pair of comb-shaped electrodes was formed by printing gold paste in a comb shape at intervals of . A commercially available ruthenium oxide glaze resistor was printed on the back side of the alumina substrate between the gold electrodes and baked to form a heater. Next, the above paste was printed on the surface of the substrate to a thickness of about 65μ, and after air drying at room temperature, it was heated to 400℃.
The mixture was gradually heated until the temperature reached , and maintained at this temperature for 1 hour. At this stage, the paste evaporated and became a sintered film of the respective oxide composition containing sulfate ions. The thickness of this gas sensitive material was approximately 60μ. A gas sensing element was thus obtained. In addition, to identify the amount of sulfate ions contained in the gas-sensitive membrane, rather than printing a portion of each of the above pastes on an alumina substrate, we slowly heated the paste at a temperature of 400°C in the same way as described above. TG−DTA
It was also subjected to fluorescent X-ray analysis. Further, the presence of sulfate ions was confirmed by analyzing the infrared absorption spectrum as in Example 1. Example 1 shows the gas sensitivity characteristics of each sensing element.
It was measured in the same way as in the case of FIGS. 4 to 6 show the relationship between the gas sensitivity (Ra/Rg) and the sulfate ions contained in samples A to C having different oxide compositions, respectively. Table 3 also shows that samples A to C contain 2 to 5 sulfate ions as representative examples of aging characteristics.
The rate of change in resistance value over time when evaluated using the same method as in Example 1 for those containing % by weight is shown. In Example 2, methane and propane were used as the test gases. As is clear from FIGS. 4 to 6, almost the same characteristics as those obtained in Example 1 are obtained even when the sensitive body is a sintered film. Furthermore, as is clear from Table 3, the rate of change in resistance value over time is also very small, as in Example 1. Further, as can be seen from FIGS. 4 to 6, if the amount of sulfate ions is less than 0.005% by weight, there is no effect of adding Sn, Zr or Ti, and the effects of the present invention cannot be expected. On the other hand, if it exceeds 10.0% by weight, it becomes impractical in terms of stability of properties or mechanical strength. The reason why the amount of sulfate ions contained in the gas sensing element of the present invention is limited to 0.005 to 10.0% by weight is based on the above-mentioned reason.
【表】
ところで、実施例１および２では出発原料とし
て市販の酸化物試薬を用いたものについて述べた
が、本発明は最終的に感応体の組成が前述した範
囲内のものであればよく、何ら出発原料や製造工
法を限定するものではない。
また実施例においては被検ガスとしてメタン
と、水素あるいはプロパンを用いたが、本発明の
効果がこれらのガスに決して限定されるものでな
く、エタン、イソブタン、アルコールといつた可
燃性ガスに対しても有効であることは勿論であ
る。
発明の効果
以上説明したように、本発明のガス検知素子は
硫酸イオンを含有するMgFe2O4に添加物として
Sn、ZrあるいはTiを添加した焼結体あるいは焼
結膜を感応体として用いたものであり、これによ
りガス感度が飛躍的に向上し、これまで貴金属触
媒を用いずには微量検知が難かしいとされてきた
メタンガスに対して、400℃という比較的低い温
度でも非常に大きい感度を実現し得るものであ
る。これは都市ガスの天然ガス（主成分：メタン
ガス）化に伴つて要求が大きくなりつつある社会
ニーズに的確に対応するものであり、その効果は
極めて大なるものがある。また、本発明のいまひ
とつの効果は寿命特性、特に通電による抵抗値の
経時変化の大幅な軽減である。これは換言すれ
ば、あらゆる検知素子の最も重要な要素である素
子の信頼性の向上に極めて大きな寄与をもたらす
ものである。[Table] By the way, in Examples 1 and 2, commercially available oxide reagents were used as starting materials, but in the present invention, the final composition of the reactor may be within the above-mentioned range. There are no limitations on starting materials or manufacturing methods. In addition, although methane, hydrogen, or propane were used as the test gases in the examples, the effects of the present invention are by no means limited to these gases, and can be applied to flammable gases such as ethane, isobutane, and alcohol. Of course, it is also effective. Effects of the Invention As explained above, the gas detection element of the present invention uses MgFe 2 O 4 containing sulfate ions as an additive.
A sintered body or sintered film doped with Sn, Zr, or Ti is used as a sensitive body, and this dramatically improves gas sensitivity, making it difficult to detect trace amounts without using a precious metal catalyst. Even at a relatively low temperature of 400 degrees Celsius, it is possible to achieve extremely high sensitivity for methane gas, which has been used for many years. This precisely responds to social needs, which are becoming increasingly demanding as city gas is replaced with natural gas (main component: methane gas), and its effects are extremely significant. Another effect of the present invention is a significant reduction in the life characteristics, especially the change in resistance value over time due to energization. In other words, this makes an extremely large contribution to improving the reliability of the element, which is the most important element of any sensing element.
第１図〜第３図は本発明の一実施例における添
加物量と、メタンおよび水素に対する感度
（Ra／Rg）ならびに抵抗経時変化率（△Ｒ）との
関係を示した特性図、第４図〜第６図は本発明の
他の実施例における硫酸イオン含有量と、メタン
およびプロパンに対する感度（Ra／Rg）との関
係を、３つの代表的な酸化物組成について示した
特性図である。
Figures 1 to 3 are characteristic diagrams showing the relationship between the amount of additives, sensitivity to methane and hydrogen (Ra/Rg), and rate of change in resistance over time (△R) in one embodiment of the present invention, and Figure 4 ~ Figure 6 is a characteristic diagram showing the relationship between the sulfate ion content and the sensitivity to methane and propane (Ra/Rg) for three representative oxide compositions in another example of the present invention.
Claims (1)
グネシウムフエライト（MgFe2O4）に、添加物と
して錫（Sn）、ジルコニウム（Zr）およびチタン
（Ti）のうち少なくともひとつが、それぞれ
SnO2、ZrO2およびTiO2に換算して添加物総量で
0.1〜50モル％含むものをガス感応体として用い
ることを特徴とするガス検知素子。 ２ ガス感応体が加圧成型し、焼成して得られる
焼結体、またはペーストを印刷して焼成して得ら
れる焼結膜であることを特徴とする特許請求の範
囲第１項記載のガス検知素子。[Claims] 1. Magnesium ferrite (MgFe 2 O 4 ) containing 0.005 to 10% by weight of sulfate ions, and at least one of tin (Sn), zirconium (Zr) and titanium (Ti) as additives. ,Each
Total amount of additives in terms of SnO 2 , ZrO 2 and TiO 2
A gas sensing element characterized in that a gas sensing element containing 0.1 to 50 mol% is used as a gas sensitive material. 2. The gas detection according to claim 1, wherein the gas sensitive body is a sintered body obtained by pressure molding and firing, or a sintered film obtained by printing and firing a paste. element.
Priority Applications (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| JP17012582A JPS5958349A (en) | 1982-09-28 | 1982-09-28 | Gas detecting element |
Applications Claiming Priority (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| JP17012582A JPS5958349A (en) | 1982-09-28 | 1982-09-28 | Gas detecting element |
Publications (2)
| Publication Number | Publication Date |
|---|---|
| JPS5958349A JPS5958349A (en) | 1984-04-04 |
| JPS6222414B2 true JPS6222414B2 (en) | 1987-05-18 |
Family
ID=15899103
Family Applications (1)
| Application Number | Title | Priority Date | Filing Date |
|---|---|---|---|
| JP17012582A Granted JPS5958349A (en) | 1982-09-28 | 1982-09-28 | Gas detecting element |
Country Status (1)
| Country | Link |
|---|---|
| JP (1) | JPS5958349A (en) |
Cited By (1)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| WO2020122074A1 (en) | 2018-12-13 | 2020-06-18 | 株式会社湯山製作所 | Tablet cassette rotor and tablet cassette |
Families Citing this family (1)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| JP7312401B2 (en) * | 2019-09-24 | 2023-07-21 | 独立行政法人国立高等専門学校機構 | Gas sensor and manufacturing method of alkaline earth ferrite |
Citations (1)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| JPS5352200A (en) * | 1976-10-22 | 1978-05-12 | Hitachi Ltd | Manufacture of gas sensor material |
-
1982
- 1982-09-28 JP JP17012582A patent/JPS5958349A/en active Granted
Patent Citations (1)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| JPS5352200A (en) * | 1976-10-22 | 1978-05-12 | Hitachi Ltd | Manufacture of gas sensor material |
Cited By (3)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| WO2020122074A1 (en) | 2018-12-13 | 2020-06-18 | 株式会社湯山製作所 | Tablet cassette rotor and tablet cassette |
| KR20210104027A (en) | 2018-12-13 | 2021-08-24 | 가부시키가이샤 유야마 세이사쿠쇼 | Rotor and tablet cassette for tablet cassettes |
| US11745954B2 (en) | 2018-12-13 | 2023-09-05 | Yuyama Mfg. Co., Ltd. | Rotor for tablet cassette and tablet cassette |
Also Published As
| Publication number | Publication date |
|---|---|
| JPS5958349A (en) | 1984-04-04 |