JPS61165652A - Combustible gas sensor - Google Patents

Abstract

PURPOSE:To obtain a combustible gas sensor having high sensitivity and excellent stability with the elapse of time and showing no change in a gas sensitivity characteristic over a long period of time, by using a gas sensor element based on SnO2 fine particles wherein the average particle size of primary particles is within a specific range. CONSTITUTION:Tin hydroxide, which was formed by adding aqueous ammonia to an aqueous SnCl4 solution, is separated and an aqueous PdCl2 solution is added to said tin hydroxide so as to adjust Pd to 0.1wt% of SnO2 while the resulting mixture is dried under heating and baked to obtain SnO2. SnO2 is ground to be mixed with an alpha-alumina powder and water is added to the resulting mixture to form a paste which is, in turn, molded into a rectangular parallelepiped, for example, with a dimension of 2.5X1.5X1.5mm equipped with an electrode. After the molded body is dried in air, a binder is dripped to the dried molded body to be penetrated therein and, after drying in air, the molded body is baked under an air atmosphere in a furnace to obtain a sensor element. By this method, a combustible gas sensor having such a particulate characteristic that the average particle size of primary SnO2 particles is within a range of 150-250Angstrom by the observation by an electronic microscope and high sensitivity and stable in a characteristic over a long period of time is obtained.

Description

【発明の詳細な説明】 産業上の利用分野 本発明は、経時安定性に優れ、長期にわたシ鋭敏なカス
感度特性を持続するＳ＃０２系可燃性カスｔ：Ｊすに関
する。DETAILED DESCRIPTION OF THE INVENTION Field of Industrial Application The present invention relates to S#02-based combustible scum t:J which has excellent stability over time and maintains sharp scum sensitivity characteristics over a long period of time.

Ｓ＃０２の焼結体をセンサ素子とする可燃性ガスｔ：／
すは、公知であシ、ガス漏れ警報器等に使用されている
。この様なガスｔ：／”ｊ素子は、例えば、アルエナｔ
ラニック基板上に形成された２ケ所の金電極を覆う様に
、５ＲＯ２粉末と高純度α−アルミナ粉末とを含む水性
ペーストを基板上に塗布し、ペーストを乾燥させた後、
空気中で焼結することにより得られている。従来使用さ
れているＳ＃０２系ガスｔ：Ｊす素子においては、透過
型電子顕微鏡により観察した焼結後のＳ　ｍ　Ｏａ−次
位子の平均粒子径が５０〜１２０Ａ程度となる様に、製
造に際して焼成条件（温度及び時間）　、　Ｓｍ０ａ原
料の粒子径等を選択している・これ拡、Ｓ＃０２−次位
子の平均粒子径があまり大きくなり過ぎると、表面積が
小さくなって酸素ガスの吸着が十分に行なわれなくなり
、センサとしての機能が十分く発揮されないと考えられ
ていたからである。しかしながら、との様な公知の５Ｉ
ＩＯ２系カスｔンサ素子には、時間の経過とともに検出
感度が鋭敏化して、当初設定した濃度以下の極微量の可
燃性ガスの存在状態で警報を発する様になるという問題
点があることが判明した。Combustible gas t using S#02 sintered body as a sensor element:/
This is well known and is used in gas leak alarms and the like. Such a gas t:/”j element is, for example, Alena t
After applying an aqueous paste containing 5RO2 powder and high purity α-alumina powder to the substrate so as to cover the gold electrodes formed at two locations on the Ranic substrate, and drying the paste,
It is obtained by sintering in air. Conventionally used S#02 series gas t:J elements are manufactured so that the average particle size of S m Oa-order particles after sintering is about 50 to 120 A as observed with a transmission electron microscope. During this process, the firing conditions (temperature and time), particle size of the Sm0a raw material, etc. are selected.If the average particle size of the S#02-next particle becomes too large, the surface area will become small and oxygen gas will not be adsorbed. This is because it was thought that the sensor function would not be performed sufficiently and the sensor function would not be fully demonstrated. However, known 5Is such as
It has been discovered that the IO2-based sensor element has a problem in that its detection sensitivity becomes more sensitive over time, causing it to issue an alarm in the presence of a trace amount of flammable gas below the initially set concentration. did.

本発明者は、公知のＳＮＯ２；Ｉｆ４カスｔンセン子に
おける検出感度の鋭敏化の発生原因について種々研究を
重ねた結果、この原因が、長期間使用中の雑ガス（調理
用アルコール、調味料の分解ガス等）との接触や電源電
圧の変動のために、ｔンサ素子が高温状態にさらされて
、５ＰＩ０２の一次粒子が次第に成長し、粗大化するこ
とによることを見出した。The present inventor has conducted various studies on the causes of increased detection sensitivity in known SNO2; It was discovered that this is due to the fact that the 5PI02 primary particles gradually grow and become coarse when the sensor element is exposed to high temperature conditions due to contact with decomposition gas, etc.) or fluctuations in power supply voltage.

そこで、本発明者は、焼結後の５ＩＷＯ２の一次粒子の
平均粒径を種々変えて各種の実験に供した結果、焼結後
の５　ｓ　Ｏ２−次粒子の平均粒子径がｆ５５．Ｇ〜２
５０Ａとなる様に調製したガスｔ＝ｚｔが、当初のガス
感度特性において従来品と同等の性能を有しており、且
つ経時安定性においては従来品を大きく凌駕することを
見出し丸。即ち、本発明は、５ＬＩＯ２を主成分とする
可燃性ガスセンサにおいて、透過型電子顕微鏡により観
察したＳ＃０２−次粒子の平均粒径が１５０〜２５０Ａ
の範囲内にあることを特徴とする可燃性カスｔ：Ｊすに
係るものである。Therefore, the present inventor conducted various experiments by varying the average particle size of the 5IWO2 primary particles after sintering, and found that the average particle size of the 5s O2 secondary particles after sintering was f55. G~2
It was discovered that the gas t = zt, which was prepared to be 50A, had the same performance as the conventional product in terms of initial gas sensitivity characteristics, and greatly exceeded the conventional product in terms of stability over time. That is, the present invention provides a combustible gas sensor containing 5LIO2 as a main component, in which the average particle size of S#02-order particles observed with a transmission electron microscope is 150 to 250A.
This relates to combustible waste t:J, which is characterized by being within the range of

本発明の可燃性ガスセンサは、焼結後の５　＃　０２−
次粒子の平均粒径が１５０〜２５０Ａの範囲内となる様
に焼結温度及び時間を調節する以外の点においては、従
来法と同様にして製造することが出来る。その１例を挙
けると、アルミすｔうニック基板上に電極材料として金
ペーストを２か所に印刷した後、同様の金ペーストを使
用して７厘−ｐｉ会全金線両電極に取シ付け、リード線
とする＠次いで、５ＩＩＯ２粉末と高純度α−アルエナ
粉末とを含む水性ペーストを上記両電極を覆う様に塗布
し、乾燥させた後、所定の温度で所定時間焼成する。透
過盤電子顕微鏡で観察した５　鱈Ｏａ−次粒子の平均粒
径を１５０〜２５０Ａの範囲内とする為には、焼成時の
温度を従来方法のそれよシも若干高くするか、又は焼成
時間を若干長くするか、或いはその両者を併用する。The combustible gas sensor of the present invention has 5#02- after sintering.
It can be produced in the same manner as the conventional method except that the sintering temperature and time are adjusted so that the average particle size of the secondary particles is within the range of 150 to 250A. To give one example, after printing gold paste as an electrode material in two places on an aluminum nick board, the same gold paste was used to attach the 7-pin all-gold wire electrodes to both electrodes. Then, an aqueous paste containing 5IIO2 powder and high-purity α-alena powder is applied to cover both electrodes, dried, and then fired at a predetermined temperature for a predetermined time. In order to keep the average particle size of cod Oa-order particles observed with a transmission disk electron microscope within the range of 150 to 250 A, the temperature during firing must be slightly higher than that of the conventional method, or the firing time must be increased. Either make it slightly longer, or use a combination of both.

発明の効果 本発明によれば、経時安定性に優れたＳ　ｎ　□　ａ糸
回燃性カスセンサが得られる。本発明ガスセンサは、ガ
ス漏れ警報器におけるｔンサとして極めて有用である。Effects of the Invention According to the present invention, a S n □ a yarn relapsed waste sensor having excellent stability over time can be obtained. The gas sensor of the present invention is extremely useful as a sensor in a gas leak alarm.

以下実施例により木発明の特徴とするところをよ〉一層
明らかにする・ 実施例１ ５ｍＣ４あの水溶液に２８　％　ＮＨ，ＯＫ　を加え、
生じた水酸化スズの沈澱を傾瀉により分離し九。次−で
、Ｐｄが５ｌｌＯ２の０．１重量−となる様にＰｄＣ４
２水溶液を加え、２００℃で４時間乾燥後、電気炉内で
空気雰囲気中、５５０’Ｃで藍時間焼成した。次いで、
焼成物を振動ボールエルにより十分に粉砕し、ｉ当な粒
度の５　ｍ　Ｏ２粉体とした後、等重量のα−アルミナ
（平均粒径ｌｏａｍｓ純度９９．９％）ｔ−混合した。The following examples will further clarify the characteristics of the wood invention. Example 1 28% NH, OK was added to that 5mC4 aqueous solution,
Separate the resulting tin hydroxide precipitate by decanting. Next, PdC4 is
After drying at 200° C. for 4 hours, it was fired at 550° C. in an electric furnace in an air atmosphere. Then,
The fired product was sufficiently pulverized with a vibrating ball-el to obtain 5 m O2 powder with a suitable particle size, and then mixed with an equal weight of α-alumina (average particle size, loams purity 99.9%).

得られた混合粉体２０１１ｇに等容量の水を加えて得た
ペーストを、ヒータ線と電極を備え九２．５ＷＸ　１．
５ＷＸ　１．５１Ｃ）直方体（成形し、１２時間風乾し
丸。次いで、十分な強度を得る為、鋏直方体にパイ：Ｊ
ｆｉ−を滴下して充分に浸潤させ丸後、６時間風乾し、
更に電気炉内で空気雰囲気中、７２５℃で３０分間焼成
して、ｔ：／す素子を得た。A paste obtained by adding an equal volume of water to 2011 g of the obtained mixed powder was prepared using a 92.5 WX 1.
5WX 1.51C) rectangular parallelepiped (molded and air-dried for 12 hours. Then, to obtain sufficient strength, cut into a scissors rectangular parallelepiped: J
After dripping fi- to fully infiltrate it, air dry it for 6 hours,
Further, it was fired in an electric furnace in an air atmosphere at 725° C. for 30 minutes to obtain a t:/S device.

かくして得られたガスｔ：Ｊｔ素子（Ｓｍ０ａの一次粒
子平均粒径１５０〜２５０Ａ）を家庭用ガス漏れ警報器
に組み込み、Ｈ２（濃度０．１　％　）及びＣＭ、　（
濃度０．１≦）に対する経時的な感度変化を測定した。The thus obtained gas t:Jt element (Sm0a primary particle average particle size 150-250A) was incorporated into a household gas leak alarm, and H2 (concentration 0.1%) and CM, (
Changes in sensitivity over time were measured for concentrations (0.1≦).

結果は、第１図の曲！ＩＡ及び第２図の曲線Ｃに示す通
シである・ Ｈ２についての結果を示す７ｇ１図において、縦軸の値
（Ｃ／Ｃｏ　）は、当初感度（Ｃ−）に対する所定時間
経過後の感度＜Ｃ＞の比を示す・又、横軸（Ｉｉ−’）
　Ｆｉ、＃、濃度０．１％、電源電ＢＥＩＩＯｒ、温度
２０℃、相対湿度６５襲なる条件下に劣化促進試験を所
定時間行なった各時点を示す・ＣＨ，についての結果を
示す第２図についても、縦軸及び横軸は、第１図の壜台
と同様のことを意味する・ 又、第１図の曲線Ｂ及び第２図の曲線りは、Ｓ＃０２−
次粒子の平均粒径５０〜１２０Ａの公知のガスセンサに
ついての結果を示す・ 曲線ＡとＢ及び曲線ＣとＤの対比から、本発明ガスｔ：
Ｊすの優れた経時安定性が明らかである。The result is the song shown in Figure 1! In Figure 7g1, which shows the results for IA and H2, which is the same as curve C in Figure 2, the value on the vertical axis (C/Co) is the sensitivity after a predetermined period of time with respect to the initial sensitivity (C-). The horizontal axis (Ii-') indicates the ratio of C>
Regarding Figure 2 showing the results for CH, which shows each point in time when the accelerated deterioration test was conducted for a predetermined time under the following conditions: Fi, #, concentration 0.1%, power supply BEIIOr, temperature 20°C, relative humidity 65%. Also, the vertical and horizontal axes mean the same things as the bottle stand in Figure 1. Also, the curve B in Figure 1 and the curve in Figure 2 are S#02-
The following results are shown for a known gas sensor with an average particle size of 50 to 120 A. From the comparison of curves A and B and curves C and D, the present invention gas t:
The excellent stability over time of Jsu is evident.

参考例１ 実施例１の方法で得た本発明ガスｔ：／すにおけ時間後
の同様の写真を第４図に示す。Reference Example 1 A similar photograph obtained by the method of Example 1 after being exposed to the gas t:/s of the present invention after a period of time is shown in FIG.

又、Ｓ＃０２−次粒子の平均粒径５０〜１２０Ａの公知
のガスセンサにおける５ＲＯ２−次粒子の透に示す。Further, the average particle size of 5RO secondary particles in a known gas sensor having an average particle diameter of 50 to 120A for S#02 secondary particles is shown in FIG.

これ等の写真からも、本発明品にかけるＳ＃０２−次粒
子の経時変化に対する安定性が明らかである。From these photographs, it is clear that the S#02-order particles applied to the product of the present invention are stable against changes over time.

【図面の簡単な説明】[Brief explanation of the drawing]

第１図及び第２図は、本発明ガスセンサの経時安定性を
従来品のそれと比較して示すグラフ、第３図及び第４図
は、劣化促進試験の前後における零発＠カスセンサ中の
５ＩＩＯ２−次粒子の状態を示す透過型電子顕微鏡写真
（４０万倍）、第５図及び第６図は、公知ガスセンサ中
のＳ＃０２−次粒子の状態を示す第３図及び第４図と同
様の写真を夫々示す。 （以　上） 代理人　弁理士　三　　枝　　英　　二・　　３、／ 第１図 第２図 峰朋　（Ｈｒ）Figures 1 and 2 are graphs showing the temporal stability of the gas sensor of the present invention in comparison with that of a conventional product. Figures 3 and 4 are graphs showing the 5IIO2- Transmission electron micrographs (400,000 times), Figures 5 and 6 showing the state of secondary particles are similar to Figures 3 and 4 showing the state of S#02 secondary particles in a known gas sensor. Show each photo. (Above) Agent: Eiji Saegusa, Patent Attorney / Figure 1, Figure 2, Minetomo (Hr)

Claims (1)

【特許請求の範囲】[Claims] （１）ＳｎＯ＿２を主成分とする可燃性ガスセンサにお
いて、透過型電子顕微鏡により観察したＳｎＯ＿２一次
粒子の平均粒径が１５０〜２５０Åの範囲内にあること
を特徴とする可燃性ガスセンサ。(1) A combustible gas sensor containing SnO_2 as a main component, characterized in that the average particle diameter of SnO_2 primary particles as observed with a transmission electron microscope is within the range of 150 to 250 Å.