JP2009236693A - Ammonia concentration measuring sensor element, ammonia concentration measuring instrument, and ammonia concentration measuring method - Google Patents

Ammonia concentration measuring sensor element, ammonia concentration measuring instrument, and ammonia concentration measuring method Download PDF

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JP2009236693A
JP2009236693A JP2008083409A JP2008083409A JP2009236693A JP 2009236693 A JP2009236693 A JP 2009236693A JP 2008083409 A JP2008083409 A JP 2008083409A JP 2008083409 A JP2008083409 A JP 2008083409A JP 2009236693 A JP2009236693 A JP 2009236693A
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ammonia concentration
sensor element
ammonia
solid electrolyte
detection
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JP5105284B2 (en
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Norio Miura
則雄 三浦
Elumalai Perumal
エルマレイ ぺルマル
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NGK Insulators Ltd
Kyushu University NUC
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Kyushu University NUC
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Abstract

<P>PROBLEM TO BE SOLVED: To provide an ammonia concentration measuring sensor element having high sensitivity and selectivity with respect to ammonia, capable of being reduced in size and enhanced in heat resistance and durability, an ammonia concentration measuring instrument and an ammonia concentration measuring method. <P>SOLUTION: The ammonia concentration measuring sensor element 11 includes a detection electrode which includes a solid electrolyte substrate 12 comprising an ion conductive solid electrolyte, the Au layer 16 formed on the solid electrolyte substrate 12 and a porous oxide layer 13 covered with the Au layer 16, the Pt reference electrode coming into contact with the solid electrolyte and a temperature regulating part for regulating the temperature of the solid electrolyte. <P>COPYRIGHT: (C)2010,JPO&INPIT

Description

本発明は、被検ガス中のアンモニア濃度を検出するアンモニアセンサ素子に関する。本発明のアンモニアセンサ素子は、例えば内燃機関の排ガス中のアンモニア濃度を測定するために用いられ、特に、尿素を添加してＮＯｘを浄化するＮＯｘ選択還元システムに好適に使用される。   The present invention relates to an ammonia sensor element that detects an ammonia concentration in a test gas. The ammonia sensor element of the present invention is used, for example, to measure the ammonia concentration in the exhaust gas of an internal combustion engine, and is particularly preferably used in a NOx selective reduction system that purifies NOx by adding urea.

ＮＯｘ等を含む自動車のエンジン等の内燃機関から排出される排ガスは、自然環境に深刻な悪影響を及ぼしている。その結果として自動車の排ガスからのＮＯｘを除去するための厳しい環境基準が国際的にも課題となってきている。こうして近年では、内燃機関、特に自動車のエンジンから排出されるＮＯｘを浄化する研究が進んでいる。例えばＳＣＲ（Ｓｅｌｅｃｔｉｖｅ Ｃａｔａｌｙｔｉｃ Ｒｅｄｕｃｔｉｏｎ）触媒に尿素を添加することによりアンモニアを発生させ、そのアンモニアによりＮＯｘを還元して排ガスを浄化する技術（ＮＯｘ選択還元システム）が開発されている。   Exhaust gas discharged from an internal combustion engine such as an automobile engine containing NOx or the like has a serious adverse effect on the natural environment. As a result, strict environmental standards for removing NOx from automobile exhaust gas have become an international issue. Thus, in recent years, research for purifying NOx discharged from an internal combustion engine, particularly an automobile engine, has been advanced. For example, a technology (NOx selective reduction system) has been developed in which ammonia is generated by adding urea to an SCR (Selective Catalytic Reduction) catalyst, NOx is reduced by the ammonia, and exhaust gas is purified.

この技術では、排出されるＮＯｘをアンモニアにより高効率で還元浄化するために、尿素の添加量を調節する必要があるので、アンモニア濃度を正確に測定する必要がある。そのため、例えばＷＯ３を主体とし、貴金属を添加した感応層を用いたアンモニアセンサ（例えば特許文献１参照）や、ＷＯ３を主体としＭｏＯ３を添加した感応層を用いたアンモニアセンサ（例えば特許文献２参照）が開示されている。 In this technique, in order to reduce and purify the exhausted NOx with ammonia with high efficiency, it is necessary to adjust the amount of urea added, so it is necessary to accurately measure the ammonia concentration. Therefore, for example, WO 3 as a main component, ammonia sensor using a sensitive layer added with noble metal (for example, see Patent Document 1) and, the ammonia sensor (for example, Patent Document Using sensitive layer was added MoO 3 as a main component WO 3 2).

また、上記アンモニアセンサは、自動車排ガス触媒のオンボード監視システムにおいて必要とされてきている。この場合、高速応答、小型、安価であることが求められ、さらに、厳しい環境下で高温でも作動する性能が求められていた。   Also, the ammonia sensor has been required in an onboard monitoring system for automobile exhaust gas catalyst. In this case, a high-speed response, a small size, and a low cost are required, and further, a performance that operates at a high temperature in a severe environment is required.

特開平５−８７７６０号公報JP-A-5-87760 特開平１０−１９８２１号公報JP-A-10-19821

しかしながら、前記特許文献１に記載のアンモニアセンサは、ＮＯ、ＮＯ２に感度があるため、尿素を添加して排ガス中のＮＯｘを還元浄化するＮＯｘ選択還元システムに使用できないという問題がある。 However, since the ammonia sensor described in Patent Document 1 is sensitive to NO and NO 2 , there is a problem that it cannot be used in a NOx selective reduction system that reduces and purifies NOx in exhaust gas by adding urea.

また、前記特許文献２に記載のアンモニアセンサでは、選択性は改善されているものの、選択性改善のために添加されているＭｏＯ３の融点が７９５℃、沸点が１１５５℃と低いため、上述したＮＯｘ選択還元システムに使用するには、耐熱性に問題があり、排ガス中で使用することは困難である。 Further, in the ammonia sensor described in Patent Document 2, although the selectivity is improved, the melting point of MoO 3 added for improving the selectivity is 795 ° C. and the boiling point is as low as 1155 ° C. When used in a NOx selective reduction system, there is a problem in heat resistance, and it is difficult to use in exhaust gas.

本発明は、前記課題を解決するためになされたものであり、アンモニアに対して感度が大きく、選択性が高く、小型化が可能で、耐熱性及び耐久性が高いアンモニア濃度測定用センサ素子、アンモニア濃度測定装置、およびアンモニア濃度測定方法を提供することを目的とする。   The present invention has been made to solve the above-mentioned problems, and has a high sensitivity to ammonia, a high selectivity, a small size, a high heat resistance and durability, and a sensor element for measuring ammonia concentration. An object of the present invention is to provide an ammonia concentration measuring device and an ammonia concentration measuring method.

即ち、本発明によれば、以下のアンモニア濃度測定用センサ素子、アンモニア濃度測定装置、およびアンモニア濃度測定方法が提供される。   That is, according to the present invention, the following ammonia concentration measuring sensor element, ammonia concentration measuring apparatus, and ammonia concentration measuring method are provided.

［１］ イオン伝導性固体電解質からなる固体電解質基板と、前記固体電解質基板上に設けられたＡｕ層と、前記Ａｕ層を被覆した多孔質酸化物層と、を含む検知極と、前記固体電解質基板上に設けられたＰｔ参照極と、前記固体電解質基板の温度調節をする温度調節部と、を含むアンモニア濃度測定用センサ素子。 [1] A detection electrode including a solid electrolyte substrate made of an ion conductive solid electrolyte, an Au layer provided on the solid electrolyte substrate, and a porous oxide layer covering the Au layer, and the solid electrolyte A sensor element for measuring ammonia concentration, comprising: a Pt reference electrode provided on a substrate; and a temperature adjusting unit for adjusting the temperature of the solid electrolyte substrate.

［２］ 前記多孔質酸化物層が多孔質ＮｉＯ層である前記［１］に記載のアンモニア濃度測定用センサ素子。 [2] The ammonia concentration measurement sensor element according to [1], wherein the porous oxide layer is a porous NiO layer.

［３］ 前記検知極は、前記固体電解質基板上に設けられた前記Ａｕ層と、Ｐｔ検知極リードと、前記Ａｕ層および前記Ｐｔ検知極リードとを被覆した多孔質酸化物層層と、を含む前記［１］または［２］に記載のアンモニア濃度測定用センサ素子。 [3] The detection electrode comprises: the Au layer provided on the solid electrolyte substrate; a Pt detection electrode lead; and a porous oxide layer layer covering the Au layer and the Pt detection electrode lead. The ammonia concentration measuring sensor element according to [1] or [2].

［４］ 前記固体電解質基板は安定化剤としてイットリアを３〜１５ｍｏｌ％添加したジルコニアからなる前記［１］〜［３］のいずれかに記載のアンモニア濃度測定用センサ素子。 [4] The ammonia concentration measurement sensor element according to any one of [1] to [3], wherein the solid electrolyte substrate is made of zirconia to which 3 to 15 mol% of yttria is added as a stabilizer.

［５］ 被検ガスを内部に導入する検知区画と、前記検知区画に設けられた前記［１］〜［４］のいずれかに記載のアンモニア濃度測定用センサ素子と、前記検知極と前記参照極との電極間の起電力差と、あらかじめ蓄積された検量線データとを比較することにより前記被検ガス中のアンモニア濃度を測定する演算部と、を含むアンモニア濃度測定装置。 [5] A detection section for introducing a gas to be detected inside, the ammonia concentration measuring sensor element according to any one of [1] to [4] provided in the detection section, the detection electrode, and the reference An ammonia concentration measuring apparatus comprising: an arithmetic unit that measures an ammonia concentration in the test gas by comparing an electromotive force difference between the electrodes and a calibration curve data accumulated in advance.

［６］ 前記検知区画が、前記検知区画内部に導入された前記被検ガスの酸素濃度を制御するための電気化学的酸素ポンプを有した前記［５］に記載のアンモニア濃度測定装置。 [6] The ammonia concentration measuring apparatus according to [5], wherein the detection section includes an electrochemical oxygen pump for controlling an oxygen concentration of the test gas introduced into the detection section.

［７］ 前記［５］に記載のアンモニア濃度測定装置を用い、前記検知区画に前記被検ガスを導入し、前記温度調節部を用いて前記固体電解質基板の温度を７５０〜８５０℃の範囲となるように制御し、前記検知極と前記参照極との電極間の起電力差を測定し、前記検知極と前記参照極との電極間の起電力差と、あらかじめ蓄積された前記検知極と前記参照極との電極間の起電力差から得られた検量線データとを比較することにより前記被検ガス中のアンモニア濃度を測定するアンモニア濃度の測定方法。 [7] Using the ammonia concentration measuring apparatus according to [5], the test gas is introduced into the detection section, and the temperature of the solid electrolyte substrate is set within a range of 750 to 850 ° C. using the temperature control unit. And measuring the electromotive force difference between the detection electrode and the reference electrode, the electromotive force difference between the detection electrode and the reference electrode, and the detection electrode accumulated in advance A method for measuring ammonia concentration, wherein the ammonia concentration in the test gas is measured by comparing calibration curve data obtained from an electromotive force difference between the reference electrode and the electrode.

［８］ 前記［６］に記載のアンモニア濃度測定装置を用い、前記検知区画に前記被検ガスを導入し、前記温度調節部を用いて前記固体電解質基板の温度を７５０〜８５０℃の範囲となるように制御し、前記電気化学的酸素ポンプを用いて前記検知区画内部に導入された前記被検ガスの酸素濃度を５〜１５ｖｏｌ．％の範囲となるように制御し、前記検知極と前記参照極との電極間の起電力差を測定し、前記検知極と前記参照極との電極間の起電力差と、あらかじめ蓄積された前記検知極と前記参照極との電極間の起電力差から得られた検量線データとを比較することにより前記被検ガス中のアンモニア濃度を測定するアンモニア濃度の測定方法。 [8] Using the ammonia concentration measuring apparatus according to [6], the test gas is introduced into the detection section, and the temperature of the solid electrolyte substrate is set within a range of 750 to 850 ° C. using the temperature control unit. The oxygen concentration of the test gas introduced into the detection section using the electrochemical oxygen pump is adjusted to 5 to 15 vol. %, The electromotive force difference between the detection electrode and the reference electrode is measured, and the electromotive force difference between the detection electrode and the reference electrode is stored in advance. A method for measuring ammonia concentration, wherein the ammonia concentration in the test gas is measured by comparing calibration curve data obtained from the electromotive force difference between the detection electrode and the reference electrode.

本発明によれば、アンモニアに対して感度が大きく、選択性が高く、小型化が可能で、耐熱性及び耐久性が高いアンモニアセンサ素子を提供することを目的とする。また、本発明のアンモニアセンサ素子を用いたアンモニア濃度測定装置、およびアンモニア濃度測定方法を用いれば、ＳＣＲ触媒に尿素を添加することによりアンモニアを発生させ、そのアンモニアによりＮＯｘを還元して排ガスを浄化する技術を従来に比して容易に実現でき、自動車排ガス等の厳しい環境基準を満たすことが可能となる。   An object of the present invention is to provide an ammonia sensor element that has high sensitivity to ammonia, high selectivity, can be miniaturized, and has high heat resistance and durability. Further, by using the ammonia concentration measuring apparatus and the ammonia concentration measuring method using the ammonia sensor element of the present invention, ammonia is generated by adding urea to the SCR catalyst, and NOx is reduced by the ammonia to purify the exhaust gas. This technology can be easily realized compared to the conventional technology, and can meet strict environmental standards such as automobile exhaust gas.

以下、図面を参照しつつ本発明の実施の形態について説明する。本発明は、以下の実施形態に限定されるものではなく、発明の範囲を逸脱しない限りにおいて、変更、修正、改良を加え得るものである。   Hereinafter, embodiments of the present invention will be described with reference to the drawings. The present invention is not limited to the following embodiments, and changes, modifications, and improvements can be added without departing from the scope of the invention.

本発明のアンモニアセンサ素子の基本的な構成の一例を図１、図２および図３Ａ、図３Ｂに示す。図３Ａは図１のアンモニアセンサ素子１１のＸ−Ｘ’断面図を示す。図３Ｂは図１のアンモニアセンサ素子１１のＹ−Ｙ’断面図を示す。本発明のアンモニアセンサ素子１１は、イオン伝導性の固体電解質からなる固体電解質基板１２と、固体電解質基板１２上に設けられたＡｕ層１６と、Ａｕ層１６の上を被覆した多孔質酸化物層１３と、を含む検知極１８と、固体電解質基板１２上に設けられたＰｔ参照極１５と、固体電解質基板１２の温度調節をする温度調節部４３と、を含むように構成される。Ｐｔ参照極１５は、参照極１９として用いられるものである。検知極１８のＡｕ層１６は、粒子状に分散し、多孔質酸化物層１３及び固体電解質基板１２へ拡散して存在する。   An example of the basic configuration of the ammonia sensor element of the present invention is shown in FIGS. 1, 2, 3A, and 3B. FIG. 3A shows a cross-sectional view of the ammonia sensor element 11 in FIG. FIG. 3B shows a Y-Y ′ cross-sectional view of the ammonia sensor element 11 of FIG. 1. The ammonia sensor element 11 of the present invention includes a solid electrolyte substrate 12 made of an ion conductive solid electrolyte, an Au layer 16 provided on the solid electrolyte substrate 12, and a porous oxide layer covering the Au layer 16 13, a Pt reference electrode 15 provided on the solid electrolyte substrate 12, and a temperature adjustment unit 43 that adjusts the temperature of the solid electrolyte substrate 12. The Pt reference electrode 15 is used as the reference electrode 19. The Au layer 16 of the detection electrode 18 is dispersed in the form of particles and diffuses into the porous oxide layer 13 and the solid electrolyte substrate 12.

本発明のアンモニアセンサ素子１１においては、検知極で用いられるＡｕ層上を被覆した多孔質酸化物層１３の酸化物としてＣｒ、Ｍｎ、Ｆｅ、Ｃｏ、Ｎｉ、Ｃｕ、Ｚｎ、Ｖ、および希土類元素から選択される少なくとも１種の元素を含む酸化物であることが好ましい。また、本発明のアンモニアセンサ素子においては、検知極で用いられるＡｕ層上を被覆した多孔質酸化物層１３の酸化物としてＣｒ、Ｍｎ、Ｆｅ、Ｃｏ、Ｎｉ、Ｃｕ、Ｚｎ、Ｖ、および希土類元素から選択される少なくとも２種の元素を含む複酸化物であることが好ましい。またさらに、本発明のアンモニアセンサ素子においては、検知極で用いられるＡｕ層上を被覆した多孔質酸化物層１３の酸化物としてＮｉＯが特に好ましい。   In the ammonia sensor element 11 of the present invention, Cr, Mn, Fe, Co, Ni, Cu, Zn, V, and rare earth elements are used as the oxide of the porous oxide layer 13 covering the Au layer used in the detection electrode. It is preferable that the oxide contains at least one element selected from. In the ammonia sensor element of the present invention, Cr, Mn, Fe, Co, Ni, Cu, Zn, V, and rare earth are used as oxides of the porous oxide layer 13 covering the Au layer used in the detection electrode. A double oxide containing at least two elements selected from the elements is preferable. Furthermore, in the ammonia sensor element of the present invention, NiO is particularly preferable as the oxide of the porous oxide layer 13 covering the Au layer used in the detection electrode.

本発明のアンモニアセンサ素子１１は、図１、図２および図３Ａ、図３Ｂに示すように、イオン伝導性の固体電解質からなる固体電解質基板１２と、固体電解質基板１２上に設けられたＡｕ層１６と、そのＡｕ層１６の上を被覆した多孔質ＮｉＯ層（多孔質酸化物層１３）、を含む検知極１８と、固体電解質基板１２上に設けられたＰｔ参照極１５と、固体電解質基板の温度調節をする温度調節部４３と、を含むように構成することが特に好ましい。   As shown in FIGS. 1, 2, 3A, and 3B, the ammonia sensor element 11 of the present invention includes a solid electrolyte substrate 12 made of an ion conductive solid electrolyte, and an Au layer provided on the solid electrolyte substrate 12. 16, a sensing electrode 18 including a porous NiO layer (porous oxide layer 13) covering the Au layer 16, a Pt reference electrode 15 provided on the solid electrolyte substrate 12, and a solid electrolyte substrate It is particularly preferable that the temperature control unit 43 includes a temperature control unit 43 that controls the temperature.

また、本発明のアンモニアセンサ素子１１において、検知極１８は、前記固体電解質基板１２上に設けられた前記Ａｕ層１６と、Ｐｔ検知極リード１７と、Ａｕ層１６およびＰｔ検知極リード１７とを被覆した多孔質ＮｉＯ層（多孔質酸化物層１３）と、を含むように構成することが好ましい。   In the ammonia sensor element 11 of the present invention, the detection electrode 18 includes the Au layer 16, the Pt detection electrode lead 17, the Au layer 16 and the Pt detection electrode lead 17 provided on the solid electrolyte substrate 12. The coated porous NiO layer (porous oxide layer 13) is preferably included.

また、本発明のアンモニアセンサ素子１１において、Ａｕ層１６は固体電解質基板１２上にスパッタ法を用いて成膜する方法、金コロイド溶液塗布法、あるいは金の前駆体を塗布し還元熱分解する方法などにより形成することが好ましい。   In the ammonia sensor element 11 of the present invention, the Au layer 16 is formed on the solid electrolyte substrate 12 using a sputtering method, a colloidal gold solution coating method, or a method in which a gold precursor is applied and reduced thermal decomposition is performed. It is preferable to form by such as.

また、本発明のアンモニアセンサ素子１１において、Ａｕ層１６とその上に形成した多孔質酸化物層１３とを焼結温度９５０〜１２００度で焼結することが好ましい。   In the ammonia sensor element 11 of the present invention, the Au layer 16 and the porous oxide layer 13 formed thereon are preferably sintered at a sintering temperature of 950 to 1200 degrees.

また、本発明のアンモニアセンサ素子１１において、固体電解質基板１２は安定化剤としてイットリアを３〜１５ｍｏｌ％添加したジルコニアからなることが好ましい。   In the ammonia sensor element 11 of the present invention, the solid electrolyte substrate 12 is preferably made of zirconia to which 3 to 15 mol% of yttria is added as a stabilizer.

また、本発明のアンモニアセンサ素子１１を用いてアンモニア濃度測定装置（図示しない）を構成することができる。この場合、被検ガスを内部に導入する検知区画（図示しない）と、前記検知区画に設けられた上述の本発明のアンモニア濃度測定用センサ素子１１と、検知極１８と参照極１９との電極間の起電力差と、あらかじめ蓄積された検量線データとを比較することにより被検ガス中のアンモニア濃度を測定する演算部と、を含み、検知極１８と参照極１９との電極間の起電力差を、あらかじめ蓄積された検量線データと比較することにより被検ガス中のアンモニア濃度を測定するアンモニア濃度測定装置を構成することができる。   Further, an ammonia concentration measuring device (not shown) can be configured using the ammonia sensor element 11 of the present invention. In this case, a detection section (not shown) for introducing the test gas into the inside, the above-described ammonia concentration measuring sensor element 11 of the present invention provided in the detection section, electrodes of the detection electrode 18 and the reference electrode 19 And an arithmetic unit that measures the ammonia concentration in the test gas by comparing the difference in electromotive force between them and the calibration curve data accumulated in advance, and the electromotive force between the electrodes of the detection electrode 18 and the reference electrode 19 is measured. By comparing the power difference with the calibration curve data accumulated in advance, an ammonia concentration measuring device that measures the ammonia concentration in the test gas can be configured.

また、本発明のアンモニアセンサ素子１１を用いてアンモニア濃度測定装置を構成する場合において、検知区画が、検知区画内部に導入された被検ガスの酸素濃度を制御するための電気化学的酸素ポンプ（図示しない）を有するように構成することが好ましい。検知区画内部の酸素濃度を一定に制御することにより、被検ガス（排ガス）中の酸素濃度に変動があった場合でも安定した精度のアンモニア濃度測定を行うことができる。   In the case where the ammonia concentration measuring device is configured using the ammonia sensor element 11 of the present invention, an electrochemical oxygen pump (in which the detection section controls the oxygen concentration of the test gas introduced into the detection section) (Not shown) is preferable. By controlling the oxygen concentration inside the detection section to be constant, even when the oxygen concentration in the test gas (exhaust gas) varies, the ammonia concentration can be measured with stable accuracy.

上述した本発明のアンモニア濃度測定装置を用いてアンモニア濃度を測定する方法においては、検知区画に被検ガスを導入し、温度調節部４３を用いて固体電解質基板１２の温度を７５０〜８５０℃の範囲となるように制御し、検知極１８と参照極１９との電極間の起電力差を測定し、検知極１８と参照極１９との電極間の起電力差と、あらかじめ蓄積された検知極１８と参照極１９との電極間の起電力差から得られた検量線データとを比較することにより被検ガス中のアンモニア濃度を測定することができる。さらに好ましくは、固体電解質基板１２の温度を７５０〜８００℃の範囲となるように制御すると良い。   In the method for measuring the ammonia concentration using the ammonia concentration measuring apparatus of the present invention described above, a test gas is introduced into the detection section, and the temperature of the solid electrolyte substrate 12 is set to 750 to 850 ° C. using the temperature adjusting unit 43. The difference between the electromotive force between the electrodes of the detection electrode 18 and the reference electrode 19 is measured, and the difference between the electromotive forces between the electrodes of the detection electrode 18 and the reference electrode 19 is detected. The ammonia concentration in the test gas can be measured by comparing the calibration curve data obtained from the electromotive force difference between the electrodes 18 and 19. More preferably, the temperature of the solid electrolyte substrate 12 may be controlled to be in the range of 750 to 800 ° C.

また、上述した本発明のアンモニア濃度測定装置を用いてアンモニア濃度を測定する方法においては、検知区画に被検ガスを導入し、温度調節部４３を用いて固体電解質基板１２の温度を７５０〜８５０℃の範囲となるように制御し、電気化学的酸素ポンプを用いて前記検知区画内部に導入された被検ガスの酸素濃度を５〜１５ｖｏｌ．％の範囲となるように制御し、検知極１８と参照極１９との電極間の起電力差を測定し、検知極１８と参照極１９との電極間の起電力差と、あらかじめ蓄積された検知極１８と参照極１９との電極間の起電力差から得られた検量線データとを比較することにより被検ガス中のアンモニア濃度を測定することが好ましい。このように、被検ガスの酸素濃度を５〜１５ｖｏｌ．％の範囲となるように制御することにより、被検ガス（排ガス）中の酸素濃度に変動があった場合でも安定した精度のアンモニア濃度測定を行うことができる。さらに好ましくは、固体電解質基板１２の温度を７５０〜８００℃の範囲となるように制御制御すると良い。   Moreover, in the method for measuring the ammonia concentration using the above-described ammonia concentration measuring apparatus of the present invention, a test gas is introduced into the detection section, and the temperature of the solid electrolyte substrate 12 is adjusted to 750 to 850 using the temperature adjusting unit 43. The oxygen concentration of the test gas introduced into the detection section by using an electrochemical oxygen pump is controlled to be in the range of 5 ° C. and 5-15 vol. %, The electromotive force difference between the electrodes of the detection electrode 18 and the reference electrode 19 is measured, and the electromotive force difference between the electrodes of the detection electrode 18 and the reference electrode 19 is stored in advance. It is preferable to measure the ammonia concentration in the test gas by comparing the calibration curve data obtained from the electromotive force difference between the detection electrode 18 and the reference electrode 19. Thus, the oxygen concentration of the test gas is set to 5 to 15 vol. By controlling to be in the range of%, stable and accurate ammonia concentration measurement can be performed even when the oxygen concentration in the test gas (exhaust gas) varies. More preferably, the temperature of the solid electrolyte substrate 12 may be controlled and controlled to be in the range of 750 to 800 ° C.

本発明のアンモニアセンサ素子の検知原理は混成電位に基づいている。検知極では、Ａｕ層および多孔質酸化物層により、ＮＨ３以外のＮＯｘ、ＣＯ、水素、炭化水素は、多く含まれる酸素と速やかに反応し、酸素と平衡の状況にある。固体電解質と、検知極を構成するＡｕ層および多孔質酸化物層と、気相との界面（三相界面）では、酸素と、ＮＨ３、あるいはＮＨ３からの派生物のみが、電位の発生に寄与する。一方、参照極では、ＮＨ３を含めて酸素と速やかに反応して、酸素と平衡の状況にある。固体電解質と、参照極と、気相との界面では、酸素のみが、電位の発生に寄与する。酸素はその他の成分に比較して充分多いため、他の成分と反応しても大きい濃度変化はなく、三相界面での電位を発生に影響しない。この結果、検知極と参照極との電位の差は、ＮＨ３の濃度による差となると、推定された。 The detection principle of the ammonia sensor element of the present invention is based on the hybrid potential. At the sensing electrode, due to the Au layer and the porous oxide layer, NOx other than NH 3 , CO, hydrogen, and hydrocarbon react quickly with a large amount of oxygen and are in equilibrium with oxygen. A solid electrolyte, and an Au layer and a porous oxide layer which constitutes the sensing electrode, the interface between the gas phase (three-phase interface), and oxygen only derivatives from NH 3 or NH 3,, occurrence of potential Contribute to. On the other hand, the reference electrode reacts quickly with oxygen including NH 3 and is in equilibrium with oxygen. At the interface between the solid electrolyte, the reference electrode, and the gas phase, only oxygen contributes to potential generation. Since oxygen is sufficiently larger than other components, there is no significant change in concentration even if it reacts with other components, and the potential at the three-phase interface is not affected. As a result, the potential difference between the detection electrode and the reference electrode was estimated to be a difference due to the concentration of NH 3 .

一般に、酸素濃度７％では、アンモニアガスが１００ｐｐｍ導入されたとしても、平衡酸素分圧では１００／７００００以下の影響であるが、本発明において用いられるＡｕ層および多孔質ＮｉＯ層のような特定の電極の場合、アンモニアガス、あるいはＮＨ３からの派生物が三相界面での還元力が優先するため、動的な現象として平衡時の影響以上の値が検出されるものである。 In general, at an oxygen concentration of 7%, even if ammonia gas is introduced at 100 ppm, the equilibrium oxygen partial pressure has an effect of 100 / 70,000 or less. However, a specific layer such as an Au layer and a porous NiO layer used in the present invention is used. In the case of an electrode, ammonia gas or a derivative derived from NH 3 is given priority over the reducing power at the three-phase interface, so that a value exceeding the influence at equilibrium is detected as a dynamic phenomenon.

以下に、本発明のアンモニアセンサ素子１１の使用方法について簡単に説明する。本実施例のアンモニアセンサ素子１１は、車両（ディーゼル車）の排ガス中のＮＯｘを低減するシステムに用いられる。   Below, the usage method of the ammonia sensor element 11 of this invention is demonstrated easily. The ammonia sensor element 11 of the present embodiment is used in a system that reduces NOx in exhaust gas from a vehicle (diesel vehicle).

具体的には、図９に示す様に、車両の排気管７１に取り付けられた酸化触媒７３上流側に、周知のＳＣＲ触媒装置７５が配置されており、このＳＣＲ触媒装置７５に（還元剤として）尿素を供給してアンモニアを発生させ、このアンモニアによって、排ガス中のＮＯｘを窒素に還元して排ガスの浄化を行う。   Specifically, as shown in FIG. 9, a well-known SCR catalyst device 75 is disposed upstream of the oxidation catalyst 73 attached to the exhaust pipe 71 of the vehicle. ) Urea is supplied to generate ammonia, and with this ammonia, NOx in the exhaust gas is reduced to nitrogen to purify the exhaust gas.

このとき、排ガスの還元浄化を効率よく行わせるためには、供給する尿素の量（従って発生するアンモニアの濃度）を調節することが必要であるので、ＳＣＲ触媒装置７５の下流側にアンモニアセンサ素子１１を配置して、ＳＣＲ触媒装置７５から排出されるアンモニアの濃度を検出する。   At this time, in order to efficiently reduce and purify the exhaust gas, it is necessary to adjust the amount of urea to be supplied (and hence the concentration of generated ammonia), so that an ammonia sensor element is provided downstream of the SCR catalyst device 75. 11 is arranged to detect the concentration of ammonia discharged from the SCR catalyst device 75.

つまり、アンモニアセンサ素子１１により検出されるアンモニア濃度が検出限界以下の場合には、尿素の供給量を増加し、一方、アンモニア濃度が検出される場合には、その濃度に応じて尿素の供給量を低減する等の制御を行うことにより、排ガスの還元浄化効率を高めることができる。   That is, when the ammonia concentration detected by the ammonia sensor element 11 is below the detection limit, the urea supply amount is increased. On the other hand, when the ammonia concentration is detected, the urea supply amount according to the concentration. By performing control such as reducing the emission, the reduction and purification efficiency of the exhaust gas can be increased.

以下、本発明を実施例に基づいてさらに詳細に説明するが、本発明はこれらの実施例に限定されるものではない。   EXAMPLES Hereinafter, although this invention is demonstrated further in detail based on an Example, this invention is not limited to these Examples.

（実施例１）本発明のアンモニアセンサ素子の基本的な構成の一例の概略、を実施例１として図１、図２および図３Ａ、３Ｂに示す。図１は、アンモニアセンサ素子１１のセンサ素子表面５１から見た模式的斜視図である。図２は、アンモニアセンサ素子１１のセンサ素子裏面５２から見た模式的斜視図である。図３Ａは図１のアンモニアセンサ素子１１のＸ−Ｘ’断面図を示す。図３Ｂは図１のアンモニアセンサ素子１１のＹ−Ｙ’断面図を示す。本発明の実施形態のアンモニアセンサ素子１１は、安定化剤としてイットリアを８ｍｏｌ％添加したジルコニアからなり、寸法が縦５０ｍｍ×横１０ｍｍ×厚さ５ｍｍである固体電解質基板１２の上に、Ａｕ層１６と、Ｐｔ検知極リード１７と、Ａｕ層１６を被覆した多孔質ＮｉＯ層（多孔質酸化物層１３）とで構成される検知極１８とを形成し、さらに参照極１９としてＰｔ参照極１５を設け、固体電解質基板１２内部に温度調節をするための温度調節部４３とを形成した。温度調節部４３は、図２に示すように、ヒーター４４およびヒーターリード４５とで構成した。   (Example 1) An example of the basic configuration of the ammonia sensor element of the present invention is shown as Example 1 in FIGS. 1, 2, 3A, and 3B. FIG. 1 is a schematic perspective view seen from the sensor element surface 51 of the ammonia sensor element 11. FIG. 2 is a schematic perspective view seen from the sensor element back surface 52 of the ammonia sensor element 11. FIG. 3A shows a cross-sectional view of the ammonia sensor element 11 in FIG. FIG. 3B shows a Y-Y ′ cross-sectional view of the ammonia sensor element 11 of FIG. 1. An ammonia sensor element 11 according to an embodiment of the present invention is made of zirconia to which 8 mol% of yttria is added as a stabilizer, and has an Au layer 16 on a solid electrolyte substrate 12 having dimensions of 50 mm length × 10 mm width × 5 mm thickness. And a detection electrode 18 composed of a Pt detection electrode lead 17 and a porous NiO layer (porous oxide layer 13) coated with the Au layer 16, and a Pt reference electrode 15 as a reference electrode 19. And a temperature adjusting unit 43 for adjusting the temperature inside the solid electrolyte substrate 12 was formed. As shown in FIG. 2, the temperature adjustment unit 43 includes a heater 44 and a heater lead 45.

具体的には、Ｐｔ参照極１５は、スクリーン印刷法を用いて、固体電解質基板１２の表面に形成し、温度１０００℃大気圧下で２時間焼結して得られた。また、Ｐｔペーストを線状に塗布して焼付け，Ｐｔ検知極リード１７および参照極リード４１を形成した。Ａｕ層１６の元となるＡｕ薄膜は、固体電解質基板１２上に室温にてＡｕを０．１Ｐａで２００秒間スパッタ法を用いて成膜することによって形成した。   Specifically, the Pt reference electrode 15 was obtained by forming it on the surface of the solid electrolyte substrate 12 using a screen printing method and sintering it at 1000 ° C. under atmospheric pressure for 2 hours. Further, the Pt paste was applied in a linear form and baked to form the Pt detection electrode lead 17 and the reference electrode lead 41. The Au thin film used as the base of the Au layer 16 was formed by depositing Au on the solid electrolyte substrate 12 at room temperature at 0.1 Pa using a sputtering method for 200 seconds.

多孔質ＮｉＯ層は、以下の条件で作成した。市販のＮｉＯ粉末をα―テルピノールとともに攪拌、ペースト状に調製した。得られたペーストを転写紙の上にスクリーン印刷法を用いて所望の形状（縦２ｍｍ×横１０ｍｍ×厚さ０．００６ｍｍ）に成形した。これを上述のスパッタ法によりＡｕ薄膜が成膜された固体電解質基板１２の上に、転写法を用いてＮｉＯ層を固体電解質基板１２上に形成した。   The porous NiO layer was created under the following conditions. A commercially available NiO powder was stirred together with α-terpinol and prepared into a paste. The obtained paste was formed on a transfer paper into a desired shape (length 2 mm × width 10 mm × thickness 0.006 mm) using a screen printing method. A NiO layer was formed on the solid electrolyte substrate 12 by using the transfer method on the solid electrolyte substrate 12 on which the Au thin film was formed by the sputtering method described above.

次に、Ａｕ薄膜と、Ａｕ薄膜の上を被覆したＮｉＯ層とが設けられた固体電解質基板１２を大気圧、温度１０００℃にて２時間焼結することにより、検知極１８を得た。このとき、ＮｉＯ層は、膜厚４μｍ以下の多孔質層となる。   Next, the detection electrode 18 was obtained by sintering the solid electrolyte substrate 12 provided with the Au thin film and the NiO layer coated on the Au thin film at atmospheric pressure and a temperature of 1000 ° C. for 2 hours. At this time, the NiO layer becomes a porous layer having a thickness of 4 μm or less.

こうして得られたアンモニアセンサ素子１１における検知極１８の断面のＳＥＭ像を図２７に示す。また、検知極１８の断面を示すｂａｃｋ−ｓｃａｔｔｅｒｉｎｇ ＳＥＭ（反射電子像）写真を図２８に示す。図２８中のＡｕのＥＤＸスペクトルを示すグラフを図２９に示す。図２７のＳＥＭ像から多孔質ＮｉＯ層の厚みは１〜４μｍとなることがわかった。図２８のｂａｃｋ−ｓｃａｔｔｅｒｉｎｇ ＳＥＭ像（反射電子像）から、真空蒸着で得られたＡｕ薄膜は、ＮｉＯ層とともに温度１０００℃で焼結されることにより、少なくとも一部はＡｕ微粒子の凝集体としてイットリア安定化ジルコニア固体電解質の表面上に分散して形成されていることがわかった。   FIG. 27 shows an SEM image of the cross section of the detection electrode 18 in the ammonia sensor element 11 thus obtained. Further, a back-scattering SEM (reflection electron image) photograph showing a cross section of the detection electrode 18 is shown in FIG. A graph showing the EDX spectrum of Au in FIG. 28 is shown in FIG. From the SEM image of FIG. 27, it was found that the thickness of the porous NiO layer was 1 to 4 μm. From the back-scattering SEM image (reflection electron image) of FIG. 28, the Au thin film obtained by vacuum deposition is sintered at a temperature of 1000 ° C. together with the NiO layer, so that at least a part thereof is an agglomerate of Au fine particles. It was found that it was dispersed on the surface of the stabilized zirconia solid electrolyte.

このようにして得られたアンモニアセンサ素子１１のアンモニアガスの各濃度による参照極１９および検知極１８における起電力差の応答特性（［起電力差Δｅｍｆ］＝［被検ガスの起電力］−［基準ガスの起電力］）のグラフを図８に示す。計測条件は、以下の通りである。測定温度：８００℃、酸素濃度：７ｖｏｌ．％、Ｈ２Ｏ濃度：５ｖｏｌ．％（ｗｅｔ ｃｏｎｄｉｔｉｏｎ）。起電力の値は、ガス導入時から基準値より上昇し始め、定常状態となるまでに数分を要した。９０％応答時間は５０秒であった。図８のグラフによれば、アンモニアガスの各濃度が２０〜１００ｐｐｍの範囲においては、起電力差−Δｅｍｆ／ｍＶが線形に推移することがわかった。 Response characteristics of the electromotive force difference between the reference electrode 19 and the detection electrode 18 according to each concentration of ammonia gas of the ammonia sensor element 11 obtained in this way ([electromotive force difference Δemf] = [electromotive force of the test gas] − [ A graph of the electromotive force of the reference gas]) is shown in FIG. The measurement conditions are as follows. Measurement temperature: 800 ° C., oxygen concentration: 7 vol. %, H 2 O concentration: 5 vol. % (Wet condition). The value of the electromotive force started to increase from the reference value from the time of gas introduction, and it took several minutes to reach a steady state. The 90% response time was 50 seconds. According to the graph of FIG. 8, it was found that the electromotive force difference −Δemf / mV changes linearly in the range where each concentration of ammonia gas is 20 to 100 ppm.

アンモニアセンサ素子１１の酸素濃度に対する応答特性を調査した。測定条件および結果を図１６〜２０に示す。各酸素濃度においてもアンモニアセンサ素子１１のアンモニアに対する選択性が示された。酸素濃度は５〜２１ｖｏｌ．％で測定可能である。好ましくは、７〜１５ｖｏｌ．％で一定とした状態で測定する。酸素濃度は電気化学的酸素ポンプを使用して制御することが好ましい。   The response characteristic of the ammonia sensor element 11 to the oxygen concentration was investigated. Measurement conditions and results are shown in FIGS. The selectivity of the ammonia sensor element 11 for ammonia was also shown at each oxygen concentration. The oxygen concentration is 5 to 21 vol. % Can be measured. Preferably, 7-15 vol. Measured in a constant state of%. The oxygen concentration is preferably controlled using an electrochemical oxygen pump.

図２１にアンモニアセンサ素子１１の、複数のアンモニア濃度ガスを導入した場合の起電力差のグラフを示す。測定条件は、測定温度：８００℃、酸素濃度：７ｖｏｌ．％、Ｈ２Ｏ濃度：５ｖｏｌ．％である。このような測定データを蓄積することにより検量線を作成し、アンモニア濃度測定装置やアンモニア濃度測定方法に適用することができる。図２２〜図２６に、各酸素濃度に対しての、複数のアンモニア濃度ガスを導入した場合の起電力差のグラフを示す。測定条件は、測定温度：８００℃、Ｈ２Ｏ濃度：５ｖｏｌ．％である。 FIG. 21 shows a graph of the electromotive force difference when a plurality of ammonia concentration gases are introduced into the ammonia sensor element 11. The measurement conditions were: measurement temperature: 800 ° C., oxygen concentration: 7 vol. %, H 2 O concentration: 5 vol. %. A calibration curve can be created by accumulating such measurement data, and can be applied to an ammonia concentration measuring apparatus and an ammonia concentration measuring method. 22 to 26 show graphs of the electromotive force difference when a plurality of ammonia concentration gases are introduced with respect to each oxygen concentration. The measurement conditions were: measurement temperature: 800 ° C., H 2 O concentration: 5 vol. %.

また、図１３〜図１５に、温度条件を７５０℃、７７５℃、８００℃とした場合の複数のガスに対するアンモニアセンサ素子１１の選択性を示す。測定条件は以下の通りである。酸素濃度：２１ｖｏｌ．％、Ｈ２Ｏ濃度：５ｖｏｌ．％、計測に用いられた各ガス濃度：４００ｐｐｍ。さらに、図３０〜図３３に、温度条件を７７５℃、８００℃、８２５℃、８５０℃とした場合の複数のガスに対するアンモニアセンサ素子１１の選択性を示す。測定条件は以下の通りである。酸素濃度：７ｖｏｌ．％、Ｈ２Ｏ濃度：５ｖｏｌ．％、計測に用いられた各ガス濃度：１００ｐｐｍ。このように、アンモニアセンサ素子１１が高温において優れたアンモニアガスに対する選択性を有していることが明らかとなった。 13 to 15 show the selectivity of the ammonia sensor element 11 for a plurality of gases when the temperature conditions are 750 ° C, 775 ° C, and 800 ° C. The measurement conditions are as follows. Oxygen concentration: 21 vol. %, H 2 O concentration: 5 vol. %, Each gas concentration used for measurement: 400 ppm. 30 to 33 show the selectivity of the ammonia sensor element 11 for a plurality of gases when the temperature conditions are 775 ° C., 800 ° C., 825 ° C., and 850 ° C. The measurement conditions are as follows. Oxygen concentration: 7 vol. %, H 2 O concentration: 5 vol. %, Each gas concentration used for measurement: 100 ppm. Thus, it became clear that the ammonia sensor element 11 has excellent selectivity for ammonia gas at high temperatures.

アンモニアセンサ素子１１の想定される実用環境では、測定対象とするアンモニアの他、自動車等の排ガス中のＮＯ，ＮＯ２、ＣＯや炭化水素ガス等の複数のガスが同時に混在した状態で含まれている。このため、実用環境においては測定対象とするガスの感受性の選択性が重要となる。実施例１のセンサ素子１１に対して複数のガス（ＮＯ２、ＮＯ、ＣＯ、ＣＨ４、Ｃ３Ｈ６、Ｃ３Ｈ８、ＮＨ３）を使用して得られた検知極１８および参照極１９の起電力差Δｅｍｆのグラフを図１０に示す。測定条件は以下の通りである。測定温度：８００℃、酸素濃度：７ｖｏｌ．％、Ｈ２Ｏ濃度：５ｖｏｌ．％、計測に用いられたＮＯ２、ＮＯ、ＣＯ、ＣＨ４、Ｃ３Ｈ６、Ｃ３Ｈ８、ＮＨ３の各ガス濃度：１００ｐｐｍ（ｗｅｔ ｃｏｎｄｉｔｉｏｎ）。 In the assumed practical environment of the ammonia sensor element 11, a plurality of gases such as NO, NO 2 , CO, and hydrocarbon gas in the exhaust gas of an automobile and the like are mixed at the same time in addition to ammonia to be measured. Yes. For this reason, the selectivity of the sensitivity of the gas to be measured is important in a practical environment. The detection electrode 18 and the reference electrode 19 obtained by using a plurality of gases (NO 2 , NO, CO, CH 4 , C 3 H 6 , C 3 H 8 , NH 3 ) for the sensor element 11 of the first embodiment. A graph of the electromotive force difference Δemf is shown in FIG. The measurement conditions are as follows. Measurement temperature: 800 ° C., oxygen concentration: 7 vol. %, H 2 O concentration: 5 vol. %, Each gas concentration of NO 2 , NO, CO, CH 4 , C 3 H 6 , C 3 H 8 , and NH 3 used for measurement: 100 ppm (wet condition).

図１０のグラフから、実施例１のセンサ素子のアンモニアガスの感受性に対する選択性が非常に高いことが示された。アンモニアガス濃度１００ｐｐｍに対する起電力差が−３４ｍＶに達しているにもかかわらず、アンモニア以外のガスに対しては、起電力差の絶対値が５ｍＶ以下あるいは無視できる値となった。   From the graph of FIG. 10, it was shown that the selectivity with respect to the sensitivity of the ammonia gas of the sensor element of Example 1 was very high. Although the electromotive force difference with respect to the ammonia gas concentration of 100 ppm reached -34 mV, the absolute value of the electromotive force difference became 5 mV or less or a negligible value for gases other than ammonia.

一般に、自動車等の排ガス中には、水蒸気が５〜１３ｖｏｌ．％含まれている。このため、水蒸気による実施例１のアンモニアセンサ素子に対する影響を調査した。アンモニアガス中の水蒸気を５〜１３ｖｏｌ．％の範囲で試験したところ、アンモニア濃度の感受性はほとんど影響を受けなかった。このようなアンモニアセンサ素子は自動車の排ガス中のアンモニア濃度測定に非常に適している。これまでにこのような特性を示すようなイットリア安定化ジルコニア固体電解質タイプの混成電位型アンモニアセンサ素子は報告されていないものである。   Generally, in the exhaust gas of automobiles, water vapor is 5 to 13 vol. %include. For this reason, the influence with respect to the ammonia sensor element of Example 1 by water vapor | steam was investigated. The water vapor in ammonia gas is 5-13 vol. When tested in the% range, the sensitivity of ammonia concentration was hardly affected. Such an ammonia sensor element is very suitable for measuring ammonia concentration in the exhaust gas of automobiles. So far, no yttria-stabilized zirconia solid electrolyte type mixed potential ammonia sensor element exhibiting such characteristics has been reported.

（比較例１）実施例１に示すアンモニアセンサ素子１１の構成から多孔質ＮｉＯ層を除く構成でアンモニアセンサ素子２１を作成した。このアンモニアセンサ素子２１を図４および図５に示す。図４は、アンモニアセンサ素子２１のセンサ素子表面５１から見た模式的斜視図である。図５は図４のアンモニアセンサ素子２１のＹ−Ｙ’断面図を示す。比較例１のアンモニアセンサ素子２１は、イットリアを安定化剤として８ｍｏｌ％添加したジルコニアからなり、寸法が縦５０ｍｍ×横１０ｍｍ×厚さ５ｍｍである固体電解質基板２２の上に、Ａｕ層２６と、Ｐｔ検知極リード２７とで構成される検知極２８とを形成し、さらにＰｔ参照極２５（参照極２９）を設け、固体電解質基板２２内部に温度調節をするための温度調節部４３（ヒーター）とを形成した。   (Comparative Example 1) An ammonia sensor element 21 was prepared by removing the porous NiO layer from the structure of the ammonia sensor element 11 shown in Example 1. This ammonia sensor element 21 is shown in FIGS. FIG. 4 is a schematic perspective view seen from the sensor element surface 51 of the ammonia sensor element 21. FIG. 5 is a Y-Y ′ cross-sectional view of the ammonia sensor element 21 of FIG. 4. The ammonia sensor element 21 of Comparative Example 1 is made of zirconia added with 8 mol% of yttria as a stabilizer, and has an Au layer 26 on a solid electrolyte substrate 22 having dimensions of 50 mm long × 10 mm wide × 5 mm thick, A temperature adjusting unit 43 (heater) for adjusting a temperature inside the solid electrolyte substrate 22 is formed by forming a detection electrode 28 composed of a Pt detection electrode lead 27 and further providing a Pt reference electrode 25 (reference electrode 29). And formed.

（比較例２）実施例１に示すアンモニアセンサ素子１１の構成からＡｕ層１６を除く構成でアンモニアセンサ素子３１を作成した。このアンモニアセンサ素子３１を図６および図７に示す。図６は、アンモニアセンサ素子３１のセンサ素子表面５１から見た模式的斜視図である。図７は図６のアンモニアセンサ素子３１のＹ−Ｙ’断面図を示す。比較例２のアンモニアセンサ素子３１は、イットリアを安定化剤として８ｍｏｌ％添加したジルコニアからなり、寸法が縦５０ｍｍ×横１０ｍｍ×厚さ５ｍｍである固体電解質基板３２の上に、Ｐｔ検知極リード３７と、Ｐｔ検知極リード３７を被覆した多孔質ＮｉＯ層３３とで構成される検知極３８とを形成し、さらに固体電解質基板３２上の検知極３８とは反対側の表面にＰｔ参照極３５（参照極３９）を設け、固体電解質基板３２内部に温度調節をするための温度調節部４３（ヒーター）とを形成した。   (Comparative Example 2) An ammonia sensor element 31 was prepared by removing the Au layer 16 from the structure of the ammonia sensor element 11 shown in Example 1. This ammonia sensor element 31 is shown in FIGS. FIG. 6 is a schematic perspective view seen from the sensor element surface 51 of the ammonia sensor element 31. FIG. 7 is a Y-Y ′ cross-sectional view of the ammonia sensor element 31 of FIG. 6. The ammonia sensor element 31 of Comparative Example 2 is made of zirconia added with 8 mol% of yttria as a stabilizer, and has a Pt detection electrode lead 37 on a solid electrolyte substrate 32 having dimensions of 50 mm in length, 10 mm in width, and 5 mm in thickness. And a detection electrode 38 composed of the porous NiO layer 33 covering the Pt detection electrode lead 37, and a Pt reference electrode 35 (on the surface opposite to the detection electrode 38 on the solid electrolyte substrate 32). A reference electrode 39) was provided, and a temperature adjustment unit 43 (heater) for adjusting the temperature inside the solid electrolyte substrate 32 was formed.

図１０、図１１、図１２はそれぞれ実施例１、比較例１、比較例２の各アンモニアセンサ素子を用いた複数のガス（ＮＯ２、ＮＯ、ＣＯ、ＣＨ４、Ｃ３Ｈ６、Ｃ３Ｈ８、ＮＨ３）に対する参照極と検知極との起電力差を示すグラフである。測定条件は以下の通り。測定温度：８００℃、酸素濃度：７ｖｏｌ．％、Ｈ２Ｏ濃度：５ｖｏｌ．％、計測に用いられたＮＯ２、ＮＯ、ＣＯ、ＣＨ４、Ｃ３Ｈ６、Ｃ３Ｈ８、ＮＨ３の各ガス濃度：１００ｐｐｍ（ｗｅｔ ｃｏｎｄｉｔｉｏｎ）。 10, 11, and 12 show a plurality of gases (NO 2 , NO, CO, CH 4 , C 3 H 6 , C 3 H 8) using the ammonia sensor elements of Example 1, Comparative Example 1, and Comparative Example 2, respectively. , NH 3 ) is a graph showing the electromotive force difference between the reference electrode and the detection electrode. The measurement conditions are as follows. Measurement temperature: 800 ° C., oxygen concentration: 7 vol. %, H 2 O concentration: 5 vol. %, Each gas concentration of NO 2 , NO, CO, CH 4 , C 3 H 6 , C 3 H 8 , and NH 3 used for measurement: 100 ppm (wet condition).

図１０、図１１、図１２のグラフから、実施例１のアンモニアセンサ素子１１のアンモニアガスに対する選択性が顕著であることが明らかとなった。   From the graphs of FIGS. 10, 11, and 12, it became clear that the selectivity of the ammonia sensor element 11 of Example 1 with respect to ammonia gas was remarkable.

本発明によれば、アンモニアに対して感度が大きく、選択性が高く、小型化が可能で、耐熱性及び耐久性が高いアンモニアセンサ素子を提供する。また、本発明のアンモニアセンサ素子を用いたアンモニア濃度測定装置、およびアンモニア濃度測定方法を提供する。   According to the present invention, an ammonia sensor element having high sensitivity to ammonia, high selectivity, miniaturization, high heat resistance and durability is provided. Also provided are an ammonia concentration measuring device and an ammonia concentration measuring method using the ammonia sensor element of the present invention.

本発明の実施の形態のアンモニアセンサ素子の表側から見た模式的斜視図である。It is the typical perspective view seen from the front side of the ammonia sensor element of embodiment of this invention. 本発明の実施の形態のアンモニアセンサ素子の裏側から見た模式的一部透過斜視図である。It is the typical partial transmission perspective view seen from the back side of the ammonia sensor element of embodiment of this invention. 図１に示す本発明の実施の形態のアンモニアセンサ素子のＸ−Ｘ’断面図である。It is X-X 'sectional drawing of the ammonia sensor element of embodiment of this invention shown in FIG. 図１に示す本発明の実施の形態のアンモニアセンサ素子のＹ−Ｙ’断面図である。FIG. 2 is a Y-Y ′ sectional view of the ammonia sensor element according to the embodiment of the present invention shown in FIG. 1. 比較例１のアンモニアセンサ素子の表側から見た模式的斜視図である。6 is a schematic perspective view of an ammonia sensor element of Comparative Example 1 as viewed from the front side. FIG. 図４に示す本発明の実施の形態のアンモニアセンサ素子のＹ−Ｙ’断面図である。FIG. 6 is a Y-Y ′ sectional view of the ammonia sensor element according to the embodiment of the present invention shown in FIG. 4. 比較例２のアンモニアセンサ素子の表側から見た模式的斜視図である。6 is a schematic perspective view of an ammonia sensor element of Comparative Example 2 viewed from the front side. FIG. 図６に示す本発明の実施の形態のアンモニアセンサ素子のＹ−Ｙ’断面図である。FIG. 7 is a Y-Y ′ sectional view of the ammonia sensor element according to the embodiment of the present invention shown in FIG. 6. 本発明の実施形態のアンモニアセンサ素子におけるアンモニア濃度と起電力の応答特性を示すグラフである。It is a graph which shows the ammonia concentration and electromotive force response characteristic in the ammonia sensor element of embodiment of this invention. 本発明のアンモニアセンサ素子の使用方法の一例を示す説明図である。It is explanatory drawing which shows an example of the usage method of the ammonia sensor element of this invention. 本発明の実施形態のアンモニアセンサ素子における複数の試料ガスの選択性を示すグラフである。It is a graph which shows the selectivity of several sample gas in the ammonia sensor element of embodiment of this invention. 比較例１のアンモニアセンサ素子における複数の試料ガスの選択性を示すグラフである。6 is a graph showing the selectivity of a plurality of sample gases in the ammonia sensor element of Comparative Example 1. 比較例２のアンモニアセンサ素子における複数の試料ガスの選択性を示すグラフである。10 is a graph showing the selectivity of a plurality of sample gases in the ammonia sensor element of Comparative Example 2. 本発明の実施形態のアンモニアセンサ素子における複数の試料ガスの選択性を示すグラフである。It is a graph which shows the selectivity of several sample gas in the ammonia sensor element of embodiment of this invention. 本発明の実施形態のアンモニアセンサ素子における複数の試料ガスの選択性を示すグラフである。It is a graph which shows the selectivity of several sample gas in the ammonia sensor element of embodiment of this invention. 本発明の実施形態のアンモニアセンサ素子における複数の試料ガスの選択性を示すグラフである。It is a graph which shows the selectivity of several sample gas in the ammonia sensor element of embodiment of this invention. 本発明の実施形態のアンモニアセンサ素子における複数の試料ガスの選択性を示すグラフである。It is a graph which shows the selectivity of several sample gas in the ammonia sensor element of embodiment of this invention. 本発明の実施形態のアンモニアセンサ素子における複数の試料ガスの選択性を示すグラフである。It is a graph which shows the selectivity of several sample gas in the ammonia sensor element of embodiment of this invention. 本発明の実施形態のアンモニアセンサ素子における複数の試料ガスの選択性を示すグラフである。It is a graph which shows the selectivity of several sample gas in the ammonia sensor element of embodiment of this invention. 本発明の実施形態のアンモニアセンサ素子における複数の試料ガスの選択性を示すグラフである。It is a graph which shows the selectivity of several sample gas in the ammonia sensor element of embodiment of this invention. 本発明の実施形態のアンモニアセンサ素子における複数の試料ガスの選択性を示すグラフである。It is a graph which shows the selectivity of several sample gas in the ammonia sensor element of embodiment of this invention. 起電力から検量線によりアンモニア濃度を測定する方法を説明するための本発明の実施形態のアンモニアセンサ素子におけるアンモニア濃度の応答特性を示すグラフである。It is a graph which shows the response characteristic of the ammonia concentration in the ammonia sensor element of embodiment of this invention for demonstrating the method to measure ammonia concentration from an electromotive force with a calibration curve. 本発明の実施形態のアンモニアセンサ素子におけるアンモニア濃度の応答特性を示すグラフである。It is a graph which shows the response characteristic of the ammonia concentration in the ammonia sensor element of embodiment of this invention. 本発明の実施形態のアンモニアセンサ素子におけるアンモニア濃度の応答特性を示すグラフである。It is a graph which shows the response characteristic of the ammonia concentration in the ammonia sensor element of embodiment of this invention. 本発明の実施形態のアンモニアセンサ素子におけるアンモニア濃度の応答特性を示すグラフである。It is a graph which shows the response characteristic of the ammonia concentration in the ammonia sensor element of embodiment of this invention. 本発明の実施形態のアンモニアセンサ素子におけるアンモニア濃度の応答特性を示すグラフである。It is a graph which shows the response characteristic of the ammonia concentration in the ammonia sensor element of embodiment of this invention. 本発明の実施形態のアンモニアセンサ素子におけるアンモニア濃度の応答特性を示すグラフである。It is a graph which shows the response characteristic of the ammonia concentration in the ammonia sensor element of embodiment of this invention. 本発明の実施形態のアンモニアセンサ素子における検知極の断面を示す図面代用ＳＥＭ写真である。It is a drawing substitute SEM photograph which shows the cross section of the detection pole in the ammonia sensor element of embodiment of this invention. 本発明の実施形態のアンモニアセンサ素子における検知極の断面を示す図面代用ｂａｃｋ−ｓｃａｔｔｅｒｉｎｇ ＳＥＭ（反射電子像）写真である。It is a back-scattering SEM (reflected electron image) photograph which substitutes for a figure which shows the cross section of the detection pole in the ammonia sensor element of embodiment of this invention. 本発明の実施形態のアンモニアセンサ素子における検知極の断面のＡｕのＥＤＸスペクトルを示すグラフである。It is a graph which shows the EDX spectrum of Au of the cross section of the detection pole in the ammonia sensor element of embodiment of this invention. 本発明の実施形態のアンモニアセンサ素子における複数の試料ガスの選択性を示すグラフである。It is a graph which shows the selectivity of several sample gas in the ammonia sensor element of embodiment of this invention. 本発明の実施形態のアンモニアセンサ素子における複数の試料ガスの選択性を示すグラフである。It is a graph which shows the selectivity of several sample gas in the ammonia sensor element of embodiment of this invention. 本発明の実施形態のアンモニアセンサ素子における複数の試料ガスの選択性を示すグラフである。It is a graph which shows the selectivity of several sample gas in the ammonia sensor element of embodiment of this invention. 本発明の実施形態のアンモニアセンサ素子における複数の試料ガスの選択性を示すグラフである。It is a graph which shows the selectivity of several sample gas in the ammonia sensor element of embodiment of this invention.

符号の説明Explanation of symbols

１１：アンモニアセンサ素子、１２：固定電解質基板、１３：多孔質酸化物層、１５：Ｐｔ参照極、１６：Ａｕ層、１７：Ｐｔ検知極リード、１８：検知極、１９：参照極、２１：アンモニアセンサ素子、２２：固定電解質基板、２５：Ｐｔ参照極、２６：Ａｕ層、２７：Ｐｔ検知極リード、２８：検知極、２９：参照極、３１：アンモニアセンサ素子、３２：固定電解質基板、３３：多孔質ＮｉＯ層、３５：Ｐｔ参照極、３７：Ｐｔ検知極リード、３８：検知極、３９：参照極、４１：参照極リード、４３：温度調節部、４４：ヒーター、４５：ヒーターリード、５１：センサ素子表面、５２：センサ素子裏面、７１：排気管、７３：酸化触媒、７５：ＳＣＲ触媒装置。 11: Ammonia sensor element, 12: Fixed electrolyte substrate, 13: Porous oxide layer, 15: Pt reference electrode, 16: Au layer, 17: Pt detection electrode lead, 18: Detection electrode, 19: Reference electrode, 21: Ammonia sensor element, 22: fixed electrolyte substrate, 25: Pt reference electrode, 26: Au layer, 27: Pt detection electrode lead, 28: detection electrode, 29: reference electrode, 31: ammonia sensor element, 32: fixed electrolyte substrate, 33: Porous NiO layer, 35: Pt reference electrode, 37: Pt detection electrode lead, 38: Detection electrode, 39: Reference electrode, 41: Reference electrode lead, 43: Temperature control unit, 44: Heater, 45: Heater lead 51: Sensor element surface, 52: Sensor element back surface, 71: Exhaust pipe, 73: Oxidation catalyst, 75: SCR catalyst device.

Claims (8)

イオン伝導性固体電解質からなる固体電解質基板と、
前記固体電解質基板上に設けられたＡｕ層と、前記Ａｕ層を被覆した多孔質酸化物層と、を含む検知極と、
前記固体電解質基板上に設けられたＰｔ参照極と、
前記固体電解質基板の温度調節をする温度調節部と、を含むアンモニア濃度測定用センサ素子。 A solid electrolyte substrate made of an ion conductive solid electrolyte;
A sensing electrode comprising an Au layer provided on the solid electrolyte substrate, and a porous oxide layer covering the Au layer;
A Pt reference electrode provided on the solid electrolyte substrate;
A sensor element for measuring ammonia concentration, comprising: a temperature adjusting unit for adjusting the temperature of the solid electrolyte substrate. 前記多孔質酸化物層が多孔質ＮｉＯ層である請求項１に記載のアンモニア濃度測定用センサ素子。   The sensor element for measuring ammonia concentration according to claim 1, wherein the porous oxide layer is a porous NiO layer. 前記検知極は、前記固体電解質基板上に設けられた前記Ａｕ層と、Ｐｔ検知極リードと、前記Ａｕ層および前記Ｐｔ検知極リードとを被覆した多孔質酸化物層と、を含む請求項１または２に記載のアンモニア濃度測定用センサ素子。   The detection electrode includes the Au layer provided on the solid electrolyte substrate, a Pt detection electrode lead, and a porous oxide layer covering the Au layer and the Pt detection electrode lead. Or the ammonia concentration measuring sensor element according to 2; 前記固体電解質基板は安定化剤としてイットリアを３〜１５ｍｏｌ％添加したジルコニアからなる請求項１〜３のいずれか１項に記載のアンモニア濃度測定用センサ素子。   The sensor element for ammonia concentration measurement according to any one of claims 1 to 3, wherein the solid electrolyte substrate is made of zirconia to which 3 to 15 mol% of yttria is added as a stabilizer. 被検ガスを内部に導入する検知区画と、
前記検知区画に設けられた請求項１〜４のいずれか１項に記載のアンモニア濃度測定用センサ素子と、
前記検知極と前記参照極との電極間の起電力差と、あらかじめ蓄積された検量線データとを比較することにより前記被検ガス中のアンモニア濃度を測定する演算部と、を含むアンモニア濃度測定装置。 A detection zone for introducing the test gas into the interior;
The sensor element for ammonia concentration measurement according to any one of claims 1 to 4, provided in the detection section,
An ammonia concentration measurement comprising: an arithmetic unit that measures an ammonia concentration in the test gas by comparing an electromotive force difference between the detection electrode and the reference electrode with a previously stored calibration curve data apparatus. 前記検知区画が、前記検知区画内部に導入された前記被検ガスの酸素濃度を制御するための電気化学的酸素ポンプを有した請求項５に記載のアンモニア濃度測定装置。   The ammonia concentration measuring apparatus according to claim 5, wherein the detection section has an electrochemical oxygen pump for controlling the oxygen concentration of the test gas introduced into the detection section. 請求項５に記載のアンモニア濃度測定装置を用い、
前記検知区画に前記被検ガスを導入し、
前記温度調節部を用いて前記固体電解質基板の温度を７５０〜８５０℃の範囲となるように制御し、
前記検知極と前記参照極との電極間の起電力差を測定し、
前記検知極と前記参照極との電極間の起電力差と、あらかじめ蓄積された前記検知極と前記参照極との電極間の起電力差から得られた検量線データとを比較することにより前記被検ガス中のアンモニア濃度を測定するアンモニア濃度の測定方法。 Using the ammonia concentration measuring device according to claim 5,
Introducing the test gas into the detection section;
Control the temperature of the solid electrolyte substrate to be in the range of 750 to 850 ° C. using the temperature adjusting unit,
Measure the electromotive force difference between the detection electrode and the reference electrode,
By comparing the electromotive force difference between the electrodes of the detection electrode and the reference electrode and the calibration curve data obtained from the electromotive force difference between the electrodes of the detection electrode and the reference electrode stored in advance. A method for measuring ammonia concentration for measuring ammonia concentration in a test gas. 請求項６に記載のアンモニア濃度測定装置を用い、
前記検知区画に前記被検ガスを導入し、
前記温度調節部を用いて前記固体電解質基板の温度を７５０〜８５０℃の範囲となるように制御し、
前記電気化学的酸素ポンプを用いて前記検知区画内部に導入された前記被検ガスの酸素濃度を５〜１５ｖｏｌ．％の範囲となるように制御し、
前記検知極と前記参照極との電極間の起電力差を測定し、
前記検知極と前記参照極との電極間の起電力差と、あらかじめ蓄積された前記検知極と前記参照極との電極間の起電力差から得られた検量線データとを比較することにより前記被検ガス中のアンモニア濃度を測定するアンモニア濃度の測定方法。 Using the ammonia concentration measuring device according to claim 6,
Introducing the test gas into the detection section;
Control the temperature of the solid electrolyte substrate to be in the range of 750 to 850 ° C. using the temperature adjusting unit,
The oxygen concentration of the test gas introduced into the detection section using the electrochemical oxygen pump is adjusted to 5 to 15 vol. % To control the range,
Measure the electromotive force difference between the detection electrode and the reference electrode,
By comparing the electromotive force difference between the electrodes of the detection electrode and the reference electrode and the calibration curve data obtained from the electromotive force difference between the electrodes of the detection electrode and the reference electrode accumulated in advance. A method for measuring ammonia concentration for measuring the ammonia concentration in a test gas.
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