JP3855776B2

JP3855776B2 - Oxygen pump element

Info

Publication number: JP3855776B2
Application number: JP2002008383A
Authority: JP
Inventors: 彪長井; 祐福田; 直子生川
Original assignee: Panasonic Corp; Matsushita Electric Industrial Co Ltd
Current assignee: Panasonic Corp; Panasonic Holdings Corp
Priority date: 2002-01-17
Filing date: 2002-01-17
Publication date: 2006-12-13
Anticipated expiration: 2022-01-17
Also published as: JP2003215093A

Description

【０００１】
【発明の属する技術分野】
本発明は集中電流による発熱をなくした酸素ポンプ素子に関するものである。
【０００２】
【従来の技術】
従来、この種の酸素ポンプ素子は、図８の（Ａ）および（Ｂ）に示すようなものが知られている。図８の（Ｂ）は、図８の（Ａ）におけるａ−ａの断面図である。酸素イオン導電性基板１の一方の表面に第１作用電極２とこの第１作用電極２の一部に第１引出電極２ａを形成し、他の表面に第２作用電極３とこの第２作用電極３の一部に第２引出電極３ａを形成したものである。また、リード線の引出電極については開示されていないが、酸素イオン電流密度が０．９Ａ／cm^２程度の酸素ポンプ素子も知られている。
【０００３】
そして、代表的な酸素イオン導電性基板１としては、イットリウムをドープしたジルコニア（ＹＳＺ）や、ガドリニアをドープしたセリア（ＧＤＣ）などがあり、第１作用電極２や第２作用電極３としては、白金や銀などの焼成電極膜などが用いられている。また、第１引出電極２ａや第２引出電極３ａとしては、第１作用電極２や第２作用電極３と同じ電極膜が用いられていた。
【０００４】
【発明が解決しようとする課題】
前記従来の酸素ポンプ素子において、第１作用電極２および第２作用電極３の電極面積が２cm2の場合、大きな酸素イオン電流（約１．８Ａ）が酸素ポンプ素子を流れるときがある。このとき、第１引出電極２ａや第２引出電極３ａは第１作用電極２、第２作用電極３の一部にしか電気的に接続されていないので大きな電流が、第１引出電極２ａや第２引出電極３ａおよびこれら引出電極近傍の第１作用電極２や第２作用電極３に集中して流れ、この結果、これらの部分が集中的に発熱するという課題があった。
【０００５】
また、この発熱により、酸素イオン導電性基板１にクラックが発生し易くなる、第１作用電極２や第２作用電極３が劣化し易くなるなどの課題も発生していた。また、酸素イオン導電性基板１の一部が集中的に上昇すると、その部分の酸素イオン導電性基板１の抵抗値が減少する結果、過大な電流が流れることに起因して酸素イオン導電性基板１も劣化し易いという課題も派生していた。
【０００６】
【課題を解決するための手段】
本発明の酸素ポンプ素子は、酸素イオン導電性基板の一方の表面に形成した第１作用電極と、第１作用電極の外縁部に接触し、第１作用電極の外縁部全体を囲むように形成された第１リード接続電極と、酸素イオン導電性基板の他の表面に形成した第２作用電極と、第２作用電極の外縁部に接触し、第２作用電極の外縁部全体を囲むように形成された第２リード接続電極とから成る構成である。
【０００７】
上記発明によれば、電流は、第１作用電極の外縁部全体に接触する第１リード接続電極や第２作用電極の外縁部全体に接触する第２リード接続電極を介して、均等に第１作用電極や第２作用電極に流入もしくは流出するので、電流は特定の場所に集中しない。
【０００８】
【発明の実施の形態】
本発明の請求項１にかかる酸素ポンプ素子は、電流が第１作用電極の外縁部に接触し、第１作用電極の外縁部全体を囲むように形成された第１リード接続電極や第２作用電極の外縁部に接触し、第２作用電極の外縁部全体を囲むように形成された第２リード接続電極を介して、第１作用電極や第２作用電極に均等に流入もしくは流出するので、電流は特定の場所に集中しない。
【０００９】
本発明の請求項２にかかる酸素ポンプ素子では、第１リード接続電極および第２リード接続電極が硝子粉末を含む導電性ペーストの焼成体であるので、緻密な電極膜が得られる。
【００１０】
本発明の請求項３にかかる酸素ポンプ素子では、酸素イオン導電性基板の一方の表面と第１リード接続電極間に第１絶縁層を設けたので、酸素イオン導電性基板に印加される直流電圧を低減し、格子酸素の脱離を低減できる。
【００１１】
本発明の請求項４にかかる酸素ポンプ素子では、第１絶縁層が第１作用電極の外縁部にまで接触しているので、第１リード接続電極の形状ばらつきにかかわらず酸素イオン導電性基板に印加される直流電圧を低減し、格子酸素の脱離を低減できる。
【００１２】
本発明の請求項５にかかる酸素ポンプ素子では、酸素イオン導電性基板の両面に絶縁層を設けたので、絶縁層にピンホールなどの欠陥が含まれていても、酸素イオン導電性基板に印加される直流電圧を低減し、格子酸素の脱離を低減できる。
【００１３】
本発明の請求項６にかかる酸素ポンプ素子では、第１絶縁層が第１作用電極の外縁部に接触し、第２絶縁層が第２作用電極の外縁部に接触しているので、第１リード接続電極の形状ばらつきや第２リード接続電極の形状ばらつきにかかわらず、第１リード接続電極と第２リード接続電極の間を電気的に分離できる。
【００１４】
本発明の請求項７にかかる酸素ポンプ装置では、第１絶縁層および第２絶縁層として硝子焼成体を用いているので、酸素イオン導電性基板への接着性に優れた絶縁膜が得られる。
【００１５】
本発明の請求項８かかる酸素ポンプ装置では、第１リード接続電極および第２リード接続電極にそれぞれ複数の外部リード線が接続されているので、電流が１本の外部リード線に集中しない。
【００１６】
本発明の請求項９にかかる酸素ポンプ装置では、複数の第１外部リード線の接続位置と複数の第２外部リード線の接続位置が対向しないので、電流が流れたとき、酸素イオン導電性基板が両面から同時に加熱されない。
【００１７】
【実施例】
以下、本発明の実施例について図面を用いて説明する。
【００１８】
（実施例１）
図１は本発明の実施例１の酸素ポンプ素子の構成を示す見取図である。また、図２は同図に示した直線ｂ−ｂで切断したときの断面図である。
【００１９】
本発明の酸素ポンプ素子は、酸素イオン導電性基板１の一方の表面に第１作用電極２と、第１作用電極２の外縁部に接触し、第１作用電極２の外縁部全体を囲むように第１リード接続電極４を形成し、酸素イオン導電性基板１の他の表面に第２作用電極３と、第２作用電極３の外縁部に接触し、第２作用電極３の外縁部全体を囲むように第２リード接続電極５形成して構成される。酸素イオン導電性基板１として、イットリウムをドープしたジルコニア（ＹＳＺ）やサマリウムをドープしたセリア（ＳＤＣ）が用いられる。例えば、第１作用電極２を正電位に、他方、第２作用電極３を負電位にして、両者間に直流電圧を印加したとき、外部雰囲気中の酸素分子は第２作用電極３によりイオン化されて、酸素イオンとして酸素イオン導電性基板１に取り込まれる。この酸素イオンは電界により引張られて、第１作用電極２に到達した後、酸素分子として外部雰囲気中に放出される。
【００２０】
このような第１作用電極２や第２作用電極３として、白金（Ｐｔ）、銀（Ａｇ）、サマリウムーストロンチウムーコバルトから成る複合金属酸化物（ＳＳＣＯ）などの導電性スパッタ膜や焼成膜、蒸着膜が用いられる。これら各種導電性膜の中でも、第１作用電極２や第２作用電極３として、酸化ビスマス粉末を含む導電性ペーストの焼成体は、適度な多孔度を有し、酸素イオン導電性基板１に対する接着力が大きく、また、生産性に優れる点で好ましい。適度な多孔度は、酸素分子のイオン化や酸素イオンの再分子化に必要である。なお、酸素ポンプ素子の場合、ポンピング性能は第１作用電極２や第２作用電極３の面積に比例して高くなるので、通常、この面積は数cm^２以上である。スパッタ膜や蒸着膜の形成には、真空装置を必要とするので、大面積膜の生産には大型装置を必要とする点で好ましくない。
【００２１】
第１作用電極２の外縁部に接触し、第１作用電極２の外縁部全体を囲むように形成された第１リード接続電極４および第２作用電極３の外縁部に接触し、第２作用電極３の外縁部全体を囲むように形成された第２リード接続電極５は、第１作用電極２や第２作用電極３と異なり、酸素分子のイオン化や酸素イオンの再分子化としての作用を要求されない。酸素分子のイオン化や酸素イオンの再分子化に伴い生じる電子電流を安定的に充分に補給することが求められる。従って、第１リード接続電極４や第２リード接続電極５として、酸素イオン導電性基板１に対する接着力が最も大きく、且つ、抵抗値の小さな緻密な導電性膜が求められるので、硝子粉末を含む導電性ペーストの焼成体が望ましい。硝子粉末は焼成時に酸素イオン導電性基板１と化学的に容易に結合して、強力な接着力を導電性焼成体に付与する。
【００２２】
第１リード接続電極４は第１作用電極２の外縁部に接触し、第１作用電極２の外縁部全体を囲むように形成され、また、第２リード接続電極５は第２作用電極３の外縁部に接触し、第２作用電極３を囲むするように形成しているので、酸素分子のイオン化や酸素イオンの再分子化に伴い生じる電子電流をそれぞれの外縁部を通じて均等に第１リード接続電極４や第２リード接続電極５に流すことができる。従って、従来例で示した電流の集中が生じ無い。
【００２３】
この電流の集中が防止されることにより、酸素イオン導電性基板１にクラックの発生が無くなるとともに第１作用電極２や第２作用電極３が発熱の集中による劣化が防止され、優れた耐久性を実現することができる。また、第１作用電極２や第２作用電極３が発熱の集中が防止されることにより、酸素イオン導電性基板１の温度も均一となり、酸素イオン導電性基板１の抵抗値の分布が均一とすることができるので酸素イオン導電性基板１の一部に過大な電流が流れることに起因して起こる酸素イオン導電性基板１も劣化が防止され、酸素ポンプとしての耐久性を向上させることができる。
【００２４】
（実施例２）
図３は本発明の実施例２の酸素ポンプ素子の構成を示す断面図である。また、図４は同図に示した直線ｃ−ｃで切断したときの断面図である。
【００２５】
本実施例では、酸素イオン導電性基板１の一方の表面に接触する第１リード接続電極４と酸素イオン導電性基板１の一方の表面間に第１絶縁層６が設けられている。
【００２６】
酸素ポンプ素子の動作時には、第１作用電極２と第２作用電極３間に直流電圧が印加される。このとき、第１リード接続電極４と第２リード接続電極５間にも同時に直流電圧が印加される。第１作用電極２と第２作用電極３間では、外部空間の酸素分子がイオン化されて、酸素イオンとして酸素イオン導電性基板１の中に取り込まれるので、酸素イオン導電性基板１は劣化しない。しかし、第１リード接続電極４と第２リード接続電極５間では、酸素イオンが酸素イオン導電性基板１の中に補給されないので、酸素イオン導電性基板１として用いる酸化物固体電解質材料（ＹＳＺなど）を構成する酸素（格子酸素）が直流電界により引張られて正電極側に移動して、そこで酸素分子として外部空間に放散する。この格子酸素の脱離は、直流電圧が高くなるにつれて指数函数的に増加する。この格子酸素の脱離により、酸素イオン導電性基板１は還元され、高い電子電導性の材料に変質する。この変質により、酸素ポンプ素子の酸素ポンピング性能は低下する。
【００２７】
本実施例では、酸素イオン導電性基板１の一方の表面に接触する第１リード接続電極４と酸素イオン導電性基板１の一方の表面間に第１絶縁層６が設けられている。第１絶縁層６として、絶縁性の高い硝子、アルミナなどのスパッタ膜や焼成膜、蒸着膜が用いられる。これら各種絶縁膜の中でも、第１絶縁層６として、硝子焼成体は、優れた絶縁瀬能有する以外にも、酸素イオン導電性基板１に対する接着力が大きく、また、生産性に優れる点で好ましい。第１絶縁層６は、酸素イオン導電性基板１に比べ一桁以上高い絶縁性を示す。従って、第１リード接続電極４と第２リード接続電極５間に直流電圧が印加されても、直流電圧の９０％以上の電圧は第１絶縁層６に印加され、酸素イオン導電性基板１には１０％以下の電圧しか印加されない。酸素イオン導電性基板１に印加される有功直流電圧の低減により、格子酸素の脱離を低減できる。
【００２８】
導電性焼成体から成る第１作用電極２や第２作用電極３および硝子焼成体から成る第１絶縁層６などは、ペーストを所定のパターンに印刷・乾燥後、空気中で焼成する工程を経て形成される。これらの焼成後パターンがある程度ばらつくことは、避けられない。このような場合でも、酸素イオン導電性基板１に印加される有功直流電圧を確実に低減させるには、図５に示すように、第１絶縁層６が第１作用電極２の外縁部２ａに接触することが好ましい。この接触部により、焼成後パターンのばらつきを吸収できるからである。
【００２９】
（実施例３）
図６は本発明の実施例３の酸素ポンプ素子の構成を示す断面図である。また、図７は同図に示した直線ｄ−ｄで切断したときの断面図である。
【００３０】
第１絶縁層６には、微少なピンホールやクラックなどの欠陥が含まれる場合がある。このような場合、図７に示すように、第１絶縁層６に加えて、酸素イオン導電性基板１の他の表面に接触する第２リード接続電極５と酸素イオン導電性基板１の他の表面間に第２絶縁層７を設けることが望ましい。第１リード接続電極４と第２リード接続電極５間に直流電圧が印加されたとき、この直流電圧は、第１絶縁層６に印加される電圧、酸素イオン導電性基板１に印加される電圧および第２絶縁層７に印加される電圧にそれぞれ分配される。
【００３１】
第１絶縁層６に欠陥が含まれる場合、この部分は絶縁されないので、第１絶縁層６に印加される電圧は零である、従って、直流電圧は、酸素イオン導電性基板１に印加される電圧と第２絶縁層７に印加される電圧にそれぞれ分配される。また、逆の場合も存在する。しかし、第１絶縁層６に含まれる欠陥と第２絶縁層７に含まれる欠陥が、酸素イオン導電性基板１を介して同じ、または、ごく近接した位置に発生する確率は小さい。従って、第１絶縁層６や第２絶縁層７に欠陥が含まれる場合でも、格子酸素の脱離を低減できる。
【００３２】
なお、図５の構成で述べたと同じ理由により、第１絶縁層６が第１作用電極２の外縁部２ａに接触し、第２絶縁層７が第２作用電極３の外縁部に接触することが好ましい。
【００３３】
また、第１リード接続電極４や第２リード接続電極５に外部リード線を接続する場合、それぞれ複数の外部リード線を接続することが望ましい。これにより、例えば、第１リード接続電極４全体に流れる電子電流を分割して外部に流すことができるので、電流を外部に取出すときの電流の集中を低減できる。
【００３４】
更に、第１リード接続電極４に接続された複数の第１外部リード線の接続位置と第２リード接続電極５に接続された複数の第２外部リード線の接続位置が対向しないことがより望ましい。複数の外部リード線を接続しても、ある程度の電流の集中は避けられない。本リード線接続構成により、第１リード接続電極４側での電流集中位置と第２リード接続電極５側での電流集中位置が異なるので、電流集中による温度上昇を低減できる。
【００３５】
【発明の効果】
以上説明したように本発明にかかる酸素ポンプ素子では、作用電極の外縁部全体に接触するようにリード接続電極を設けているので、作用電極での電流の集中や引出し電極での電流の集中を低減でき、この電流の集中が防止されることにより、酸素イオン導電性基板１にクラックの発生が無くなるとともに第１作用電極２や第２作用電極３が発熱の集中による劣化が防止され、優れた耐久性を実現することができる。また、第１作用電極２や第２作用電極３が発熱の集中が防止されることにより、酸素イオン導電性基板１の温度も均一となり、酸素イオン導電性基板１の抵抗値の分布が均一とすることができるので酸素イオン導電性基板１の一部に過大な電流が流れることに起因して起こる酸素イオン導電性基板１も劣化が防止され、酸素ポンプとしての耐久性を向上させることができる。
【００３６】
また、酸素イオン導電性基板に印加される有功直流電圧の低減により、格子酸素の脱離を低減できる。
【００３７】
また、複数の外部リード線を設けているので、電流を外部に取出すときの電流集中を低減できる。
【図面の簡単な説明】
【図１】本発明の実施例１における酸素ポンプ素子の構成を示す見取図
【図２】本発明の実施例１における酸素ポンプ素子のｂ−ｂ断面図
【図３】本発明の実施例２における酸素ポンプ素子の構成を示す見取図
【図４】本発明の実施例２における酸素ポンプ素子のｃ−ｃ断面図
【図５】本発明の実施例２における酸素ポンプ素子の他の構成を示す断面図
【図６】本発明の実施例３における酸素ポンプ素子の構成を示す見取図
【図７】本発明の実施例３における酸素ポンプ素子のｄ−ｄ断面図
【図８】（Ａ）従来の酸素ポンプ素子の構成を示す見取図
（Ｂ）従来の酸素ポンプ素子のａ−ａ断面図
【符号の説明】
１酸素イオン導電性基板
２第１作用電極
３第２作用電極
４第１リード接続電極
５第２リード接続電極
６第１絶縁層
７第２絶縁層[0001]
BACKGROUND OF THE INVENTION
The present invention relates to an oxygen pump element that eliminates heat generation due to concentrated current.
[0002]
[Prior art]
Conventionally, oxygen pump elements of this type are known as shown in FIGS. 8A and 8B. FIG. 8B is a cross-sectional view taken along the line aa in FIG. A first working electrode 2 and a first extraction electrode 2a are formed on a part of the first working electrode 2 on one surface of the oxygen ion conductive substrate 1, and a second working electrode 3 and the second working electrode are formed on the other surface. A second extraction electrode 3 a is formed on a part of the electrode 3. Further, although no lead wire extraction electrode is disclosed, an oxygen pump element having an oxygen ion current density of about 0.9 A / cm ² is also known.
[0003]
Typical examples of the oxygen ion conductive substrate 1 include zirconia doped with yttrium (YSZ), ceria doped with gadolinia (GDC), and the like. As the first working electrode 2 and the second working electrode 3, A fired electrode film such as platinum or silver is used. Moreover, the same electrode film as the 1st working electrode 2 and the 2nd working electrode 3 was used as the 1st extraction electrode 2a and the 2nd extraction electrode 3a.
[0004]
[Problems to be solved by the invention]
In the conventional oxygen pump element, when the electrode area of the first working electrode 2 and the second working electrode 3 is 2 cm 2, a large oxygen ion current (about 1.8 A) may flow through the oxygen pump element. At this time, since the first extraction electrode 2a and the second extraction electrode 3a are electrically connected to only a part of the first working electrode 2 and the second working electrode 3, a large current is generated by the first extraction electrode 2a and the second extraction electrode 3a. There is a problem that the two extraction electrodes 3a and the first working electrode 2 and the second working electrode 3 in the vicinity of these extraction electrodes flow in a concentrated manner, and as a result, these portions generate heat intensively.
[0005]
Further, due to this heat generation, the oxygen ion conductive substrate 1 is likely to be cracked, and the first working electrode 2 and the second working electrode 3 are likely to be deteriorated. Further, when a part of the oxygen ion conductive substrate 1 is intensively increased, the resistance value of the oxygen ion conductive substrate 1 at that part decreases, and as a result, an excessive current flows, resulting in the oxygen ion conductive substrate 1 being reduced. The problem that No. 1 is easily deteriorated was also derived.
[0006]
[Means for Solving the Problems]
The oxygen pump element of the present invention is formed so as to contact a first working electrode formed on one surface of an oxygen ion conductive substrate and an outer edge of the first working electrode and surround the entire outer edge of the first working electrode. The first lead connection electrode, the second working electrode formed on the other surface of the oxygen ion conductive substrate, and the outer edge of the second working electrode so as to surround the entire outer edge of the second working electrode. The second lead connection electrode is formed.
[0007]
According to the above-described invention, the current is evenly supplied through the first lead connection electrode that contacts the entire outer edge portion of the first working electrode and the second lead connection electrode that contacts the entire outer edge portion of the second working electrode. Since it flows into or out of the working electrode or the second working electrode, the current does not concentrate at a specific location.
[0008]
DETAILED DESCRIPTION OF THE INVENTION
In the oxygen pump element according to claim 1 of the present invention, the first lead connection electrode and the second action electrode are formed so that the current contacts the outer edge of the first working electrode and surrounds the entire outer edge of the first working electrode. Since it flows into or out of the first working electrode and the second working electrode through the second lead connection electrode formed so as to contact the outer edge of the electrode and surround the entire outer edge of the second working electrode, The current does not concentrate at a specific location.
[0009]
In the oxygen pump element according to claim 2 of the present invention, since the first lead connection electrode and the second lead connection electrode are fired bodies of conductive paste containing glass powder, a dense electrode film can be obtained.
[0010]
In the oxygen pump element according to claim 3 of the present invention, since the first insulating layer is provided between the one surface of the oxygen ion conductive substrate and the first lead connection electrode, the direct current voltage applied to the oxygen ion conductive substrate. And lattice oxygen desorption can be reduced.
[0011]
In the oxygen pump element according to claim 4 of the present invention, since the first insulating layer is in contact with the outer edge portion of the first working electrode, the oxygen ion conductive substrate is formed regardless of the shape variation of the first lead connection electrode. The applied DC voltage can be reduced, and lattice oxygen desorption can be reduced.
[0012]
In the oxygen pump element according to claim 5 of the present invention, since the insulating layers are provided on both surfaces of the oxygen ion conductive substrate, even if the insulating layer includes defects such as pinholes, it is applied to the oxygen ion conductive substrate. The direct current voltage can be reduced, and lattice oxygen desorption can be reduced.
[0013]
In the oxygen pump element according to claim 6 of the present invention, the first insulating layer is in contact with the outer edge portion of the first working electrode, and the second insulating layer is in contact with the outer edge portion of the second working electrode. Regardless of the shape variation of the lead connection electrode and the shape variation of the second lead connection electrode, the first lead connection electrode and the second lead connection electrode can be electrically separated.
[0014]
In the oxygen pump device according to the seventh aspect of the present invention, since the glass fired body is used as the first insulating layer and the second insulating layer, an insulating film excellent in adhesion to the oxygen ion conductive substrate can be obtained.
[0015]
In the oxygen pump device according to the eighth aspect of the present invention, since a plurality of external lead wires are connected to the first lead connection electrode and the second lead connection electrode, current does not concentrate on one external lead wire.
[0016]
In the oxygen pump device according to claim 9 of the present invention, the connection positions of the plurality of first external lead wires and the connection positions of the plurality of second external lead wires do not face each other, so that when an electric current flows, the oxygen ion conductive substrate Are not heated from both sides simultaneously.
[0017]
【Example】
Embodiments of the present invention will be described below with reference to the drawings.
[0018]
Example 1
FIG. 1 is a sketch showing the configuration of an oxygen pump element according to Embodiment 1 of the present invention. FIG. 2 is a cross-sectional view taken along the line bb shown in FIG.
[0019]
The oxygen pump element of the present invention is in contact with the first working electrode 2 and the outer edge of the first working electrode 2 on one surface of the oxygen ion conductive substrate 1 so as to surround the entire outer edge of the first working electrode 2. to the first lead connecting electrode 4 is formed, a second working electrode 3 on the other surface of the oxygen ion conductive substrate 1, in contact with the outer edge of the second working electrode 3, the entire outer edge of the second working electrode 3 The second lead connection electrode 5 is formed so as to surround the electrode. As the oxygen ion conductive substrate 1, yttrium-doped zirconia (YSZ) or samarium-doped ceria (SDC) is used. For example, when a DC voltage is applied between the first working electrode 2 at a positive potential and the second working electrode 3 at a negative potential, oxygen molecules in the external atmosphere are ionized by the second working electrode 3. Thus, oxygen ions are taken into the oxygen ion conductive substrate 1. The oxygen ions are pulled by the electric field, reach the first working electrode 2, and are then released as oxygen molecules into the external atmosphere.
[0020]
Examples of the first working electrode 2 and the second working electrode 3 include conductive sputtered films such as platinum (Pt), silver (Ag), and samarium-strontium-cobalt (SSCO) and other sputtered films and fired films. A vapor deposition film is used. Among these various conductive films, a fired body of a conductive paste containing bismuth oxide powder as the first working electrode 2 and the second working electrode 3 has an appropriate porosity and adheres to the oxygen ion conductive substrate 1. It is preferable in terms of high strength and excellent productivity. A moderate porosity is necessary for ionization of oxygen molecules and re-molecularization of oxygen ions. In the case of an oxygen pump element, the pumping performance is increased in proportion to the area of the first working electrode 2 and the second working electrode 3, and therefore this area is usually several cm ² or more. Since the formation of the sputtered film or the vapor deposition film requires a vacuum apparatus, it is not preferable in that a large apparatus is required for the production of a large area film.
[0021]
The first working electrode 2 is in contact with the outer edge of the first working electrode 2 and the outer edges of the first working electrode 2 are formed so as to surround the entire outer edge of the first working electrode 2. Unlike the first working electrode 2 and the second working electrode 3, the second lead connection electrode 5 formed so as to surround the entire outer edge of the electrode 3 acts as an ionization of oxygen molecules and a remolecularization of oxygen ions. Not required. It is required to stably and sufficiently replenish the electron current generated with the ionization of oxygen molecules and the remolecularization of oxygen ions. Accordingly, as the first lead connection electrode 4 and the second lead connection electrode 5, a dense conductive film having the greatest adhesion to the oxygen ion conductive substrate 1 and a small resistance value is required. A fired body of conductive paste is desirable. The glass powder is chemically easily bonded to the oxygen ion conductive substrate 1 at the time of firing, and gives a strong adhesive force to the conductive fired body.
[0022]
The first lead connection electrode 4 is formed to contact the outer edge of the first working electrode 2 and surround the entire outer edge of the first working electrode 2, and the second lead connection electrode 5 is formed of the second working electrode 3. Since it is formed so as to be in contact with the outer edge and surround the second working electrode 3, the electron current generated by ionization of oxygen molecules and re-molecularization of oxygen ions is evenly connected to the first lead through each outer edge. It can flow to the electrode 4 or the second lead connection electrode 5. Therefore, the current concentration shown in the conventional example does not occur.
[0023]
By preventing this current concentration, the generation of cracks in the oxygen ion conductive substrate 1 is eliminated, and the first working electrode 2 and the second working electrode 3 are prevented from being deteriorated due to the concentration of heat generation. Can be realized. Further, since the concentration of heat generation in the first working electrode 2 and the second working electrode 3 is prevented, the temperature of the oxygen ion conductive substrate 1 becomes uniform, and the resistance value distribution of the oxygen ion conductive substrate 1 becomes uniform. Therefore, deterioration of the oxygen ion conductive substrate 1 caused by excessive current flowing in a part of the oxygen ion conductive substrate 1 is also prevented, and durability as an oxygen pump can be improved. .
[0024]
(Example 2)
FIG. 3 is a cross-sectional view showing the configuration of the oxygen pump element according to Embodiment 2 of the present invention. FIG. 4 is a cross-sectional view taken along the line cc shown in FIG.
[0025]
In this embodiment, a first insulating layer 6 is provided between the first lead connection electrode 4 that contacts one surface of the oxygen ion conductive substrate 1 and one surface of the oxygen ion conductive substrate 1.
[0026]
During the operation of the oxygen pump element, a DC voltage is applied between the first working electrode 2 and the second working electrode 3. At this time, a DC voltage is simultaneously applied between the first lead connection electrode 4 and the second lead connection electrode 5. Between the first working electrode 2 and the second working electrode 3, oxygen molecules in the external space are ionized and taken into the oxygen ion conductive substrate 1 as oxygen ions, so that the oxygen ion conductive substrate 1 does not deteriorate. However, since oxygen ions are not replenished into the oxygen ion conductive substrate 1 between the first lead connection electrode 4 and the second lead connection electrode 5, an oxide solid electrolyte material (YSZ or the like) used as the oxygen ion conductive substrate 1 is used. Oxygen (lattice oxygen) that is) is pulled by the DC electric field and moves to the positive electrode side, where it is dissipated as oxygen molecules to the external space. This desorption of lattice oxygen increases exponentially as the DC voltage increases. By this desorption of lattice oxygen, the oxygen ion conductive substrate 1 is reduced and transformed into a highly electron conductive material. Due to this alteration, the oxygen pumping performance of the oxygen pump element is reduced.
[0027]
In this embodiment, a first insulating layer 6 is provided between the first lead connection electrode 4 that contacts one surface of the oxygen ion conductive substrate 1 and one surface of the oxygen ion conductive substrate 1. As the first insulating layer 6, a sputtered film such as highly insulating glass or alumina, a fired film, or a deposited film is used. Among these various insulating films, as the first insulating layer 6, a glass fired body is preferable in terms of having high adhesion to the oxygen ion conductive substrate 1 and excellent productivity, in addition to having excellent insulating ability. The first insulating layer 6 exhibits an insulating property that is one digit higher than that of the oxygen ion conductive substrate 1. Therefore, even if a DC voltage is applied between the first lead connection electrode 4 and the second lead connection electrode 5, a voltage of 90% or more of the DC voltage is applied to the first insulating layer 6 and applied to the oxygen ion conductive substrate 1. Only a voltage of 10% or less is applied. By reducing the effective DC voltage applied to the oxygen ion conductive substrate 1, the desorption of lattice oxygen can be reduced.
[0028]
The first working electrode 2 and the second working electrode 3 made of a conductive fired body, the first insulating layer 6 made of a glass fired body, and the like are subjected to a step of firing in air after printing and drying the paste in a predetermined pattern. It is formed. It is inevitable that these baked patterns vary to some extent. Even in such a case, in order to reliably reduce the effective DC voltage applied to the oxygen ion conductive substrate 1, the first insulating layer 6 is formed on the outer edge 2a of the first working electrode 2 as shown in FIG. It is preferable to contact. This is because variations in the pattern after firing can be absorbed by this contact portion.
[0029]
Example 3
FIG. 6 is a cross-sectional view showing the configuration of the oxygen pump element according to Embodiment 3 of the present invention. FIG. 7 is a cross-sectional view taken along the line dd shown in FIG.
[0030]
The first insulating layer 6 may include defects such as minute pinholes and cracks. In such a case, as shown in FIG. 7, in addition to the first insulating layer 6, the second lead connection electrode 5 in contact with the other surface of the oxygen ion conductive substrate 1 and the other of the oxygen ion conductive substrate 1 It is desirable to provide the second insulating layer 7 between the surfaces. When a DC voltage is applied between the first lead connection electrode 4 and the second lead connection electrode 5, the DC voltage is applied to the first insulating layer 6 and the voltage applied to the oxygen ion conductive substrate 1. And the voltage applied to the second insulating layer 7.
[0031]
When the first insulating layer 6 includes a defect, this portion is not insulated, so the voltage applied to the first insulating layer 6 is zero. Therefore, a DC voltage is applied to the oxygen ion conductive substrate 1. The voltage and the voltage applied to the second insulating layer 7 are respectively distributed. The reverse case also exists. However, the probability that the defect included in the first insulating layer 6 and the defect included in the second insulating layer 7 occur at the same or very close positions through the oxygen ion conductive substrate 1 is small. Therefore, even when the first insulating layer 6 and the second insulating layer 7 include defects, the desorption of lattice oxygen can be reduced.
[0032]
For the same reason as described in the configuration of FIG. 5, the first insulating layer 6 is in contact with the outer edge portion 2 a of the first working electrode 2, and the second insulating layer 7 is in contact with the outer edge portion of the second working electrode 3. Is preferred.
[0033]
In addition, when connecting external lead wires to the first lead connection electrode 4 and the second lead connection electrode 5, it is desirable to connect a plurality of external lead wires, respectively. Thereby, for example, since the electron current flowing through the entire first lead connection electrode 4 can be divided and allowed to flow outside, the concentration of current when the current is taken out can be reduced.
[0034]
Further, it is more desirable that the connection positions of the plurality of first external lead wires connected to the first lead connection electrode 4 and the connection positions of the plurality of second external lead wires connected to the second lead connection electrode 5 do not face each other. . Even if a plurality of external leads are connected, a certain amount of current concentration cannot be avoided. With this lead wire connection configuration, the current concentration position on the first lead connection electrode 4 side is different from the current concentration position on the second lead connection electrode 5 side, so that temperature rise due to current concentration can be reduced.
[0035]
【The invention's effect】
As described above, in the oxygen pump element according to the present invention, since the lead connection electrode is provided so as to be in contact with the entire outer edge portion of the working electrode, the current concentration at the working electrode and the current concentration at the extraction electrode are reduced. By preventing this current concentration, the generation of cracks in the oxygen ion conductive substrate 1 is eliminated, and the first working electrode 2 and the second working electrode 3 are prevented from being deteriorated due to the concentration of heat generation. Durability can be realized. Further, since the concentration of heat generation in the first working electrode 2 and the second working electrode 3 is prevented, the temperature of the oxygen ion conductive substrate 1 becomes uniform, and the resistance value distribution of the oxygen ion conductive substrate 1 becomes uniform. Therefore, deterioration of the oxygen ion conductive substrate 1 caused by excessive current flowing in a part of the oxygen ion conductive substrate 1 is also prevented, and durability as an oxygen pump can be improved. .
[0036]
In addition, desorption of lattice oxygen can be reduced by reducing the effective DC voltage applied to the oxygen ion conductive substrate.
[0037]
In addition, since a plurality of external lead wires are provided, current concentration when the current is taken out can be reduced.
[Brief description of the drawings]
FIG. 1 is a schematic diagram showing the configuration of an oxygen pump element according to Embodiment 1 of the present invention. FIG. 2 is a cross-sectional view taken along line bb of the oxygen pump element according to Embodiment 1 of the present invention. FIG. 4 is a cross-sectional view of the oxygen pump element according to the second embodiment of the present invention. FIG. 5 is a cross-sectional view illustrating another structure of the oxygen pump element according to the second embodiment of the present invention. 6 is a schematic diagram showing the configuration of an oxygen pump element according to Embodiment 3 of the present invention. FIG. 7 is a cross-sectional view taken along the line dd of the oxygen pump element according to Embodiment 3 of the present invention. (B) A cross-sectional view of a conventional oxygen pump element taken along line aa [Explanation of symbols]
DESCRIPTION OF SYMBOLS 1 Oxygen ion conductive substrate 2 1st working electrode 3 2nd working electrode 4 1st lead connection electrode 5 2nd lead connection electrode 6 1st insulating layer 7 2nd insulating layer

Claims

A first working electrode formed on one surface of the oxygen ion conductive substrate, and a first lead connection formed so as to contact the outer edge of the first working electrode and surround the entire outer edge of the first working electrode An electrode, a second working electrode formed on the other surface of the oxygen ion conductive substrate, and an outer edge portion of the second working electrode so as to surround the entire outer edge portion of the second working electrode. An oxygen pump element having a second lead connection electrode.

The oxygen pump element according to claim 1, wherein the first lead connection electrode and the second lead connection electrode are made of a fired body of a conductive paste containing glass powder.

3. The oxygen according to claim 1, wherein a first insulating layer is provided between the first lead connection electrode contacting one surface of the oxygen ion conductive substrate and the one surface of the oxygen ion conductive substrate. Pump element.

The oxygen pump element according to claim 3, wherein the first insulating layer is in contact with the outer edge portion of the first working electrode.

The first lead connection electrode that contacts one surface of the oxygen ion conductive substrate and the first insulating layer between one surface of the oxygen ion conductive substrate, the second lead connection electrode that contacts the other surface, and the other surface The oxygen pump element according to claim 1, wherein a second insulating layer is provided therebetween.

The oxygen pump element according to claim 5, wherein the first insulating layer is in contact with the outer edge portion of the first working electrode, and the second insulating layer is in contact with the outer edge portion of the second working electrode.

The oxygen pump element according to any one of claims 3 to 6, wherein the first insulating layer and the second insulating layer are made of a glass fired body.

The oxygen pump element according to any one of claims 1 to 7, wherein a plurality of external lead wires are connected to the first lead connection electrode and the second lead connection electrode, respectively.

The connection position of the plurality of first external lead wires connected to the first lead connection electrode and the connection position of the plurality of second external lead wires connected to the second lead connection electrode are defined as non-opposing positions. The oxygen pump element described.