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WO1992012105A1 - Solid ceramic electrolyte for electrochemical purposes, especially for gas sensors, and process for making it - Google Patents

Solid ceramic electrolyte for electrochemical purposes, especially for gas sensors, and process for making it Download PDF

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Publication number
WO1992012105A1
WO1992012105A1 PCT/DE1991/000938 DE9100938W WO9212105A1 WO 1992012105 A1 WO1992012105 A1 WO 1992012105A1 DE 9100938 W DE9100938 W DE 9100938W WO 9212105 A1 WO9212105 A1 WO 9212105A1
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Prior art keywords
ceramic
solid electrolyte
oxide
stabilizer
gas sensors
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PCT/DE1991/000938
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German (de)
French (fr)
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Karl-Hermann Friese
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Robert Bosch Gmbh
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Publication of WO1992012105A1 publication Critical patent/WO1992012105A1/en

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    • G—PHYSICS
    • G01—MEASURING; TESTING
    • G01N—INVESTIGATING OR ANALYSING MATERIALS BY DETERMINING THEIR CHEMICAL OR PHYSICAL PROPERTIES
    • G01N27/00—Investigating or analysing materials by the use of electric, electrochemical, or magnetic means
    • G01N27/26—Investigating or analysing materials by the use of electric, electrochemical, or magnetic means by investigating electrochemical variables; by using electrolysis or electrophoresis
    • G01N27/403—Cells and electrode assemblies
    • G01N27/406—Cells and probes with solid electrolytes
    • G01N27/407—Cells and probes with solid electrolytes for investigating or analysing gases
    • G01N27/4073—Composition or fabrication of the solid electrolyte
    • C—CHEMISTRY; METALLURGY
    • C04—CEMENTS; CONCRETE; ARTIFICIAL STONE; CERAMICS; REFRACTORIES
    • C04B—LIME, MAGNESIA; SLAG; CEMENTS; COMPOSITIONS THEREOF, e.g. MORTARS, CONCRETE OR LIKE BUILDING MATERIALS; ARTIFICIAL STONE; CERAMICS; REFRACTORIES; TREATMENT OF NATURAL STONE
    • C04B35/00—Shaped ceramic products characterised by their composition; Ceramics compositions; Processing powders of inorganic compounds preparatory to the manufacturing of ceramic products
    • C04B35/01—Shaped ceramic products characterised by their composition; Ceramics compositions; Processing powders of inorganic compounds preparatory to the manufacturing of ceramic products based on oxide ceramics
    • C04B35/48—Shaped ceramic products characterised by their composition; Ceramics compositions; Processing powders of inorganic compounds preparatory to the manufacturing of ceramic products based on oxide ceramics based on zirconium or hafnium oxides, zirconates, zircon or hafnates
    • C04B35/486—Fine ceramics
    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
    • H01M8/00—Fuel cells; Manufacture thereof
    • H01M8/10—Fuel cells with solid electrolytes
    • H01M8/12—Fuel cells with solid electrolytes operating at high temperature, e.g. with stabilised ZrO2 electrolyte
    • H01M8/124—Fuel cells with solid electrolytes operating at high temperature, e.g. with stabilised ZrO2 electrolyte characterised by the process of manufacturing or by the material of the electrolyte
    • H01M8/1246—Fuel cells with solid electrolytes operating at high temperature, e.g. with stabilised ZrO2 electrolyte characterised by the process of manufacturing or by the material of the electrolyte the electrolyte consisting of oxides
    • H01M8/1253—Fuel cells with solid electrolytes operating at high temperature, e.g. with stabilised ZrO2 electrolyte characterised by the process of manufacturing or by the material of the electrolyte the electrolyte consisting of oxides the electrolyte containing zirconium oxide
    • Y—GENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
    • Y02—TECHNOLOGIES OR APPLICATIONS FOR MITIGATION OR ADAPTATION AGAINST CLIMATE CHANGE
    • Y02E—REDUCTION OF GREENHOUSE GAS [GHG] EMISSIONS, RELATED TO ENERGY GENERATION, TRANSMISSION OR DISTRIBUTION
    • Y02E60/00—Enabling technologies; Technologies with a potential or indirect contribution to GHG emissions mitigation
    • Y02E60/30—Hydrogen technology
    • Y02E60/50—Fuel cells
    • Y—GENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
    • Y02—TECHNOLOGIES OR APPLICATIONS FOR MITIGATION OR ADAPTATION AGAINST CLIMATE CHANGE
    • Y02P—CLIMATE CHANGE MITIGATION TECHNOLOGIES IN THE PRODUCTION OR PROCESSING OF GOODS
    • Y02P70/00—Climate change mitigation technologies in the production process for final industrial or consumer products
    • Y02P70/50—Manufacturing or production processes characterised by the final manufactured product

Definitions

  • Solid electrolyte ceramics for electrochemical applications in particular for gas sensors, and methods for their production
  • the invention is based on a solid electrolyte ceramic for electrochemical applications, in particular for gas sensors, according to the preamble of the main claim.
  • a solid electrolyte ceramic for electrochemical applications, in particular for gas sensors, according to the preamble of the main claim.
  • Such substances are known to be used for the formation of ion-conducting shaped bodies, which can be, for example, platelet-shaped or finger-shaped, have electrodes and possibly protective layers on their opposite surfaces and can be used as measuring sensors in exhaust gases, for example from motor vehicles.
  • Essential conditions that are placed on the solid electrolyte ceramic concern the mechanical properties, such as strength and temperature shock resistance, and the electrical properties, in particular the ion conductivity.
  • the zirconium dioxide usually used as the solid electrolyte can occur in at least three modifications, the cubic high-temperature modification, the tetragonal and the monoclinic modification, which have significant differences in properties, in particular also with regard to the mechanical and electrical properties mentioned above. Because of the good strength and ionic conductivity, the tetragonal zirconium dioxide modification for the production of solid electrolyte bodies for electrochemical applications has prevailed.
  • a zirconium dioxide ceramic whose crystal grains have a phase comprising a tetragonal phase is known, for example, from EP 0 036 786.
  • the ceramic according to the invention with the features of the main claim has the advantage over known solid electrolyte materials that good mechanical properties, in particular strength and resistance to temperature changes, as well as a reduced and permanent contact resistance to electrodes applied to it, are achieved without the need for several solid electrolyte layers.
  • the solid electrolyte ceramic obtained thereafter has, on the one hand, areas with a lower stabilizer content, which ensure high mechanical strength and thermal shock resistance, and, on the other hand, areas with a high stabilizer content, which also lead to a sufficiently high oxygen ion conductivity and phase stability ... area of the solid electrolyte ceramic.
  • the stabilizer oxide concentrations are partially compensated for by diffusion, which results in an improvement in the sintering behavior.
  • the ceramic powder with a low stabilizer oxide content must be at least 2 mol-1 below the full stabilization and the difference in stabilizer oxide content between low and highly stabilized powders must be at least 1 mol%.
  • Weight ratios between low and highly stabilized powders of 2: 1 to 1: 2 have proven particularly useful.
  • Powders with approximately the same grain size distribution and approximately the same specific surface are advantageously used.
  • fluxes such as, for example, kaolin
  • kaolin can advantageously be used between 0.5 and 2% by weight, or other clay substances.
  • oxidic additives such as aluminum oxide can advantageously be added in an amount of 0.5 to 5% by weight.
  • the solid electrolyte ceramic according to the invention and the method for its production can advantageously be used for exhaust gas sensors, in particular for motor vehicles. It is equally suitable for finger-shaped as for plate-shaped sensors, for La-mbda probes and for polarographic, so-called limit current probes.
  • Age-stable probe characteristics can be achieved with the aid of the solid electrolyte ceramic according to the invention.
  • Figure 1 shows a solid electrolyte ceramic with an overlying cermet electrode according to the prior art described in DE-OS 29 04 069, whereas
  • FIG. 2 shows a solid electrolyte ceramic according to the present invention, with a cermet electrode above it.
  • the solid electrolyte body carries an intermediate layer 22 made of fully stabilized zirconium dioxide on a partially steelized layer 21.
  • the solid electrolyte body according to the invention consists of partially stabilized portions 21 and fully stabilized / cubic portions 23.
  • the cubic portions 23 form ion-conducting bridges in the solid electrolyte ceramic 20 to the cermet electrode 10, in particular to the ceramic support structure 12 thereof, which is preferably based on cubic zirconium dioxide is.
  • the cermet electrode 10 contains, in addition to the ceramic supporting structure, metal portions 11, preferably made of platinum, and has pores and sockets 13. From the comparison of the invention with the prior art in the drawings, it can be seen that, according to the invention, the highly stabilized portions 23 of the solid electrolyte ceramic improve the ion conductivity.
  • the ceramic powders given in the table below in the specified mixing ratios are particularly suitable for the solid electrolyte ceramic according to the invention and the process for its production:
  • the solid electrolyte ceramic according to Example 1 is described in more detail below.
  • Commercially available zirconium dioxide powder which contains 97 mol% zirconium dioxide and 3 mol% yttrium oxide, with impurities of up to 0.2 wt admissible impurity mixed, the two powders being used in a weight ratio of 1: 1.
  • the powder mixture is ground together in a vibratome mill to a specific surface of approximately 10 g, pressed to a shaped body, and then sintered at 1400 ° C.
  • Metallic or cermet electrodes and further layers, for example protective layers, can be applied in a known manner to the solid electrolyte body thus obtained before or after the sintering process.

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Abstract

The proposal is for a solid ceramic electrolyte for electrochemical purposes in which at least two standard commercial ceramic powders with different stabiliser oxide components are used. According to the invention, this provides a solid ceramic electrolyte in a simple production process which unites the advantageous properties of the ceramic powders used, especially the great mechanical strength and resistance to temperature fluctuations of partially stabilised zirconium dioxide ceramic with the good ion conductivity of fully stabilised cubic zirconium dioxide ceramic. The use of the solid ceramic electrolyte of the invention in gas sensors ensures a lower and more durable transition resistance between the solid electrolyte and the electrode.

Description

Festelektrolytkeramik für elektrochemische Anwendungen, insbesondere für Gassensoren, sowie Verfahren zu ihrer Herstellung  Solid electrolyte ceramics for electrochemical applications, in particular for gas sensors, and methods for their production
Stand der Technik State of the art
Die Erfindung geht aus von einer Festelektrolytkeramik für elektrochemische Anwendungen, insbesondere für Gassensoren, nach der Gattung des Hauptanspruches. Derartige Stoffe dienen bekannterweise zur Ausbildung von ionenleitenden Formkörpεrn, die zum Beispiel plättchen- oder fingerförmig sein können, auf ihren einander gegenüberliegenden Oberflächen Elektroden und gegebenenfalls Schutzschichten tragen und als Meßfühler in Abgasen, zum Beispiel von Kraftfahrzeugen, eingesetzt werden können. Wesentliche Bedingungen, die dabei an die Festelektrolytkeramik gestellt werden, betreffen die mechanischen Eigenschaften, wie Festigkeit und Temperaturschockfestigkeit sowie die elektrischen Eigenschaften, insbesondere die Ionenleitfähigkeit. The invention is based on a solid electrolyte ceramic for electrochemical applications, in particular for gas sensors, according to the preamble of the main claim. Such substances are known to be used for the formation of ion-conducting shaped bodies, which can be, for example, platelet-shaped or finger-shaped, have electrodes and possibly protective layers on their opposite surfaces and can be used as measuring sensors in exhaust gases, for example from motor vehicles. Essential conditions that are placed on the solid electrolyte ceramic concern the mechanical properties, such as strength and temperature shock resistance, and the electrical properties, in particular the ion conductivity.
Es ist bekannt, daß das als Festelektrolyt üblicherweise eingesetzte Zirkoniumdioxid in zumindest drei Modifikationen auftreten kann, der kubischen Hochtemperaturmodifikation, der tetragonalen und der monoklinen Modifikation, die wesentliche Eigenschaftsunterschiede aufweisen, insbesondere auch in Bezug auf die oben erwähntenmechani¬schen und elektrischen Eigenschaften. Aufgrund der guten Festigkeit und Ionenleitfähigkeit hat sich die tetragonale Zirkoniumdioxid-Modifikation zur Herstellung von Festelektrolytkörpern für elektrochemische Anwendungen durchgesetzt. Ene Zirkoniumdioxid-Keramik, deren Kristallkörner eine tetragonale Phase umfassende Phase aufweisen, ist z.B. aus der EP 0 036 786 bekannt. Dabei tritt jedoch der Nachteil auf, daß ausgehend von der Oberfläche der tetragonalen Festelektrolytkeramik eine irreversible Phasenumwandlung in die monokline Modifikation auftritt, und dabei Gefügeschäden entstehen können. Durch die Umwandlung der tetragonalen in die weniger regelmäßige monokline Modifikation nimmt andererseits die Ionenleitfähigkeit wesentlich ab. Es wurde daner in der DE-OS 29 04 069 vorgeschlagen, auf eine Festelektrolytschicht aus teilstabilisierter Zirkoniumdioxidkeramik eine Zwischenschicht aus vollstabilisiertem Zirkoniumdioxid aufzubringen. It is known that the zirconium dioxide usually used as the solid electrolyte can occur in at least three modifications, the cubic high-temperature modification, the tetragonal and the monoclinic modification, which have significant differences in properties, in particular also with regard to the mechanical and electrical properties mentioned above. Because of the good strength and ionic conductivity, the tetragonal zirconium dioxide modification for the production of solid electrolyte bodies for electrochemical applications has prevailed. A zirconium dioxide ceramic whose crystal grains have a phase comprising a tetragonal phase is known, for example, from EP 0 036 786. However, there is the disadvantage that, starting from the surface of the tetragonal solid electrolyte ceramic, an irreversible phase transition into the monoclinic modification occurs, and structural damage can occur. By converting the tetragonal to the less regular monoclinic modification, on the other hand, the ion conductivity decreases significantly. It was also proposed in DE-OS 29 04 069 to apply an intermediate layer of fully stabilized zirconium dioxide to a solid electrolyte layer made from partially stabilized zirconium dioxide ceramic.
Vorteile der Erfindung Advantages of the invention
Die erfindungsgemäßp Keramik mit den Merkmalen des Hauptanspruchs hat gegenüber bekannten Festelektrolytstoffen den Vorteil, daß gute mechanische Eigenschaften, insbesondere Festigkeit und Temperaturwechselbeständigkeit sowie ein verringerter und dauerbeständiger Übergangswiderstand zu darauf aufgebrachten Elektroden erreicht werden, ohne daß mehrere Festelektrolytschichten notwendig sind. Durch die Verwendung von mindestens zwei handelsüblichen Keramikpulvern mit unterschiedlichen Stabilisatoroxidanteilen werden die vorteilhaften Eigenschaften von hoch- und niedrigstabilisierten Keramikarten vereint, und dazu ein einfaches Verfahren eingesetzt. Die danach erhaltene Festelektrolytkeramik weist zum einem Bereiche mit niedrigerem Stabilisatorgehalt auf, die eine hohe mechanische Festigkeit und Temperaturschockfestigkeit gewährleisten, und zum anderen Bereiche mit hohem Stabilisatorgehalt, die zu einer ausreichend hohen Sauerstoffionenieitfähigkeit und Phasenstabilitat auch in der Ober... flächenzone der Festelektrolytkeramik führen. In den Randzonen zwischen den Bereichen mit unterschiedlichem Stabilisatoroxidgehalt findet zudem durch Diffusion ein teilweiser Ausgleich der Stabilisatoroxidkonzentrationen statt, woraus sich eine Verbesserung des Sinterverhaltens ergibt. The ceramic according to the invention with the features of the main claim has the advantage over known solid electrolyte materials that good mechanical properties, in particular strength and resistance to temperature changes, as well as a reduced and permanent contact resistance to electrodes applied to it, are achieved without the need for several solid electrolyte layers. By using at least two commercially available ceramic powders with different proportions of stabilizer oxide, the advantageous properties of highly and low-stabilized types of ceramic are combined and a simple process is used for this. The solid electrolyte ceramic obtained thereafter has, on the one hand, areas with a lower stabilizer content, which ensure high mechanical strength and thermal shock resistance, and, on the other hand, areas with a high stabilizer content, which also lead to a sufficiently high oxygen ion conductivity and phase stability ... area of the solid electrolyte ceramic. In the marginal zones between the areas with different stabilizer oxide content, the stabilizer oxide concentrations are partially compensated for by diffusion, which results in an improvement in the sintering behavior.
Um die oben erwähnten Vorteile zu erreichen, müssen die Keramikpulver mit niedrigem Stabilisatoroxidgehalt um mindestens 2 Mol-1, unterhalb der Vollstabilisierung liegen und der Unterschied der Stabilisatoroxidanteile zwischen niedrig- und hochstabilisierten Pulvern mindestens 1 Mol-% betragen. In order to achieve the advantages mentioned above, the ceramic powder with a low stabilizer oxide content must be at least 2 mol-1 below the full stabilization and the difference in stabilizer oxide content between low and highly stabilized powders must be at least 1 mol%.
Als besonders vorteilhaft hat es sich erwiesen, handelsübliche Keramikpulver mit einem Stabilisatoroxidanteil von 0 bis 5 Mol% mit handelsüblichen Keramikpulvern mit einem Stabilisatorgehalt zwischen 5 und 8 Mol-% zur Herstellung der erfindungsgemäßen Festelektrolytkeramik einzusetzen. It has proven to be particularly advantageous to use commercially available ceramic powders with a stabilizer oxide content of 0 to 5 mol% with commercially available ceramic powders with a stabilizer content between 5 and 8 mol% to produce the solid electrolyte ceramic according to the invention.
Dabei haben sich Gewichts-Verhältnisse zwischen niedrig- und hoch¬stabilisierten Pulvern von 2 : 1 bis 1 : 2 besonders bewährt. Weight ratios between low and highly stabilized powders of 2: 1 to 1: 2 have proven particularly useful.
In vorteilhafter Weise werden Pulver mit annähernd gleicher Korngrößenverteilung und annähernd in gleicher spezifischer Oberfläche eingesetzt. Powders with approximately the same grain size distribution and approximately the same specific surface are advantageously used.
Zur Verbesserung der Sinterfähigkeit können Flußmittel, wie zum Eeispiel Kaolin, in vorteilhafter Weise zwischen 0,5 und 2 Gew-%, oder anderer Tonsubstanzen eingesetzt werden. To improve the sinterability, fluxes, such as, for example, kaolin, can advantageously be used between 0.5 and 2% by weight, or other clay substances.
Zur Verbesserung der mechanischen Festigkeit können oxidische Zusätze, wie zum Beispiel Aluminiumoxid, in vorteilhafter Weise zu 0,5 bis 5 Gew-%, zugegeben werden. Die erfindungsgemäße Festelektrolytkeramik sowie das Verfahren zur ihrer Herstellung können in vorteilhafter Weise für Abgassensoren, insbesondere für Kraftfahrzeuge, eingesetzt werden. Sie eignet sich gleichermaßen für finger- wie für plättchenförmige Sensoren, für La-mbda-Sonden sowie für polarographische, sogenannte Grenzstromsonden. To improve the mechanical strength, oxidic additives such as aluminum oxide can advantageously be added in an amount of 0.5 to 5% by weight. The solid electrolyte ceramic according to the invention and the method for its production can advantageously be used for exhaust gas sensors, in particular for motor vehicles. It is equally suitable for finger-shaped as for plate-shaped sensors, for La-mbda probes and for polarographic, so-called limit current probes.
Mit Hilfe der erfindungsgemäßen Festelektrolytkeramik lassen sich alterungsstabile Sondencharakteristiken erreichen. Age-stable probe characteristics can be achieved with the aid of the solid electrolyte ceramic according to the invention.
Zeichnung drawing
Die Zeichnung dient der näheren Erläuterung der Erfindung. The drawing serves to explain the invention in more detail.
Figur 1 stellt eine Festelektrolytkeramik mit darüberliegender Cermet-Elektrode nach dem in der DE-OS 29 04 069 beschriebenen Stand der Technik dar, wogegen  Figure 1 shows a solid electrolyte ceramic with an overlying cermet electrode according to the prior art described in DE-OS 29 04 069, whereas
Figur 2 eine Festelektrolytkeramik gemäß vorliegender Erfindung, mit darüberliegender Cermet-Elektrode, darstellt.  FIG. 2 shows a solid electrolyte ceramic according to the present invention, with a cermet electrode above it.
Gemäß der DE-OS 29 04 069 (Fig.1) trägt der Festelektrolytkörper auf einer teilstahilisierten Schicht 21 eine Zwischenschicht 22 aus vollstabilisiertem Zirkoniumdioxid. Demgegenüber besteht der erfindungsgemäße Festelektrolytkörper aus teilstabilisierten Anteilen 21 und vollstabilisierten/kubischen Anteilen 23. Die kubischen Anteile 23 bilden ionenleitende Brücken in der Festelektolytkeramik 20 zur Cermet-Elektrode 10, insbesondere zum Keramik-Stützgerüst 12 derselben, das vorzugsweise auf der Basis von kubischem Zirkoniumdioxid aufgebaut ist. Die Cermet-Elektrode 10 enthält in bekannter Weise, zusätzlich zum Keramik-Stützgerüst, Metall-Anteile 11, vorzugsweise aus Platin, und weist Poren und Sσalten 13 auf. Aus der Gegenüberstellung der Erfindung zum Stand der Technik in den Zeichnungen ist also zu erkennen, daß erfindungsgemäß durch die hochstabilisierten Anteile 23 der Festelektrolytkeramik eine Verbesserung der Ionenleitfähigkeit erreicht wird. According to DE-OS 29 04 069 (FIG. 1), the solid electrolyte body carries an intermediate layer 22 made of fully stabilized zirconium dioxide on a partially steelized layer 21. In contrast, the solid electrolyte body according to the invention consists of partially stabilized portions 21 and fully stabilized / cubic portions 23. The cubic portions 23 form ion-conducting bridges in the solid electrolyte ceramic 20 to the cermet electrode 10, in particular to the ceramic support structure 12 thereof, which is preferably based on cubic zirconium dioxide is. In a known manner, the cermet electrode 10 contains, in addition to the ceramic supporting structure, metal portions 11, preferably made of platinum, and has pores and sockets 13. From the comparison of the invention with the prior art in the drawings, it can be seen that, according to the invention, the highly stabilized portions 23 of the solid electrolyte ceramic improve the ion conductivity.
Beschreibung der Ausführungsbeispiele Description of the embodiments
Für die erfindungsgemäße Festelektrolytkeramik und das Verfahren zu ihrer Herstellung sind die in der nachfolgenden Tabelle angegebenen Keramikpulver in den angegebenen Mischungsverhältnissen, besonders geeignet: The ceramic powders given in the table below in the specified mixing ratios are particularly suitable for the solid electrolyte ceramic according to the invention and the process for its production:
ZrO -Keramik- ZrO -Keramik MischungsBeispiel pulver pulver verhältnisZrO ceramic ZrO ceramic Mixing example powder to powder ratio
Nr. mit niedrigem Stabi mit hohem Stabili (Gew. -teile lisatoroxidanteil satoroxidanteil No. with low stabilization with high stabiliz
(Mol-% Stabilisatoroxid) (Mol-% Stabilisatoroxid) 1 3Y2 O3 5Y2O3 1 : 1(Mol% stabilizer oxide) (Mol% stabilizer oxide) 1 3Y 2 O 3 5Y 2 O 3 1: 1
2 3Y2O3 8Y2O3 2 : 12 3Y 2 O 3 8Y 2 O 3 2: 1
3 5Y2O3 8Y2O3 2 : 13 5Y 2 O 3 8Y 2 O 3 2: 1
4 3Y2O3 + 5Y2O3 8Y2O3 1 : 1 : 14 3Y 2 O 3 + 5Y 2 O 3 8Y 2 O 3 1: 1: 1
5 0 8Y2O3 1 : 25 0 8Y 2 O 3 1: 2
6 0 + 5Y2O3 8Y2O3 1 : 1 :16 0 + 5Y 2 O 3 8Y 2 O 3 1: 1: 1
7 3Y2O3 5Yb2O3 1 : 17 3Y 2 O 3 5Yb 2 O 3 1: 1
8 3Y2O3 8Yb2O3 2 : 1 9 3Y2O3 8Y2O3 + 8Yb2O3 3 : 1 : 18 3Y 2 O 3 8Yb 2 O 3 2: 1 9 3Y 2 O 3 8Y 2 O 3 + 8Yb 2 O 3 3: 1: 1
10 3Y2O3 + 5Y2O3 8Yb2O3 1 : 1 : 1 Die Festelektrolytkeramik nach Beispiel 1 wird im folgenden näher beschrieben. Handelsübliches Zirkoniumdioxidpulver, das 97 Mol-% Zirkoniumdioxid und 3 Mol-% Yttriumoxid enthält, wobei Verunreinigungen bis zu 0,2 Gew.-% erlaubt sind, wird mit handelsüblichem Zirkoniumdioxidpulver aus 95 Mol-% Zirkoniumdioxid und 5 Mol-% Yttriumoxid, gleicher maximal zulässiger Verunreinigung vermischt, wobei die beiden Pulver in Gewichtsverhältnis 1 : 1 eingesetzt werden. Das Pulvergemisch wird in einer Vibratom-Mühle auf eine spezifische Oberfläche von annähernd 10 g gemeinsam aufgemahlen, zu einem Formkörper verpreßt, und anschließend bei 1400 °C gesintert. Auf den so erhaltenen Festelektrolytkörper können in bekannter Weise metallische oder Cermet-Elektroden und weitere Schichten, zum Beispiel Schutzschichten, vor oder nach dem Sinterprozeß aufgebracht werden. 10 3Y 2 O 3 + 5Y 2 O 3 8Yb 2 O 3 1: 1: 1 The solid electrolyte ceramic according to Example 1 is described in more detail below. Commercially available zirconium dioxide powder, which contains 97 mol% zirconium dioxide and 3 mol% yttrium oxide, with impurities of up to 0.2 wt admissible impurity mixed, the two powders being used in a weight ratio of 1: 1. The powder mixture is ground together in a vibratome mill to a specific surface of approximately 10 g, pressed to a shaped body, and then sintered at 1400 ° C. Metallic or cermet electrodes and further layers, for example protective layers, can be applied in a known manner to the solid electrolyte body thus obtained before or after the sintering process.
Die in den weiteren Beispielen angegebenen Pulver werden in der gleichen Weise verarbeitet. The powders given in the further examples are processed in the same way.

Claims

Ansprüche Expectations
1. Festelektrolytkeramik mit wenigstens einem Stabilisatoroxid für elektrochemische Anwendungen, insbesondere für Gassensoren, vorzugsweise auf der Basis von Zirkoniumdioxid, dadurch gekennzeichnet, daß sie mindestens zwei Keramikpulver mit unterschiedlichen Stεbilisatoroxidanteilen enthält, daß der Stabilisatoroxidanteil des einen Pulvers zumindest 2 Mol-% unterhalb des zur Vollstabilisierung notwendigen Anteils liegt und daß die Stabilisatcrcxidanteile der Keramikpulver um mindestens 1 Mol-% voneinander abweichen. 1. Solid electrolyte ceramic with at least one stabilizer oxide for electrochemical applications, in particular for gas sensors, preferably based on zirconium dioxide, characterized in that it contains at least two ceramic powders with different stabilizer oxide proportions that the stabilizer oxide content of one powder is at least 2 mol% below that for full stabilization necessary proportion and that the stabilizer oxide proportions of the ceramic powder differ from one another by at least 1 mol%.
2. Festeiektroiytkeramik nach Anspruch 1, dadurch gekennzeichnet, daß mindestens ein Keramikpulver einen Stabilisatoroxidanteil von 0 bis 5 Mol-% Yttriumoxid, Ytterbiumoxid, Yttriumoxid-Konzentrat und/oder Ytterbiumoxid-Konzentrat enthält, und mindestens ein Keramikpulver 5 bis 8 Mol-% Yttriumoxid, Ytterbiumoxid, Yttriumoxid-Konzentrat und/oder Ytterbiumoxid-Konzentrat enthält. 2. Festiektroiytkeramik according to claim 1, characterized in that at least one ceramic powder contains a stabilizer oxide content of 0 to 5 mol% of yttrium oxide, ytterbium oxide, yttrium oxide concentrate and / or ytterbium oxide concentrate, and at least one ceramic powder 5 to 8 mol% of yttrium oxide, Contains ytterbium oxide, yttrium oxide concentrate and / or ytterbium oxide concentrate.
3. Festelektrolytkeramik nach einem der vorhergehenden Ansprüche, dadurch gekennzeichnet, daß das Mischungs-Verhältnis zwichen den Keramikpulvern mit niedrigem Stabilisatoroxidanteil und mit hohem Stabilisatoroxidanteil zwischen 2 : 1 und 1 : 2 Gewichtsanteilen liegt. 3. Solid electrolyte ceramic according to one of the preceding claims, characterized in that the mixing ratio between the ceramic powders with a low stabilizer oxide content and with a high stabilizer oxide content is between 2: 1 and 1: 2 parts by weight.
4. Festelektrolytkeramik nach einem der vorhergehenden Ansprüche, dadurch gekennzeichnet, daß die Keramikpulver eine annähernd gleiche Korngrößenverteilung aufweisen. 4. Solid electrolyte ceramic according to one of the preceding claims, characterized in that the ceramic powders have an approximately equal grain size distribution.
5. Festelektrolytkeramik nach einem der vorhergehenden Ansprüche, dadurch gekennzeichnet, daß die Keramikpulver eine annähernd gleiche spezifische Oberfläche aufweisen. 5. Solid electrolyte ceramic according to one of the preceding claims, characterized in that the ceramic powder have an approximately the same specific surface.
6. Festelektrolytkeramik nach einem der vorhergehenden Ansprüche, dadurch gekennzeichnet, daß sie zusätzlich Flußmittel, insbesondere 0,5 bis 2 Gew.-% Kaolin oder andere Tonsubstanzen, enthält. 6. Solid electrolyte ceramic according to one of the preceding claims, characterized in that it additionally contains flux, in particular 0.5 to 2% by weight of kaolin or other clay substances.
7. Festelektrolytkeramik nach einem der vorhergehenden Ansprüche, dadurch gekennzeichnet, daß sie zusätzlich Stoffe zur Verbesserung der mechanischen Festigkeit, insbesondere 0,5 bis 5 Gev. -% Aluminiumoxid enthält. 7. Solid electrolyte ceramic according to one of the preceding claims, characterized in that it additionally contains substances to improve the mechanical strength, in particular 0.5 to 5 Gev. -% contains aluminum oxide.
8. Verfahren zur Herstellung einer Festelektrolytkeramik vorzugsweise auf der Basis von Zirkoniumdioxid für elektrochemische Anwendungen, insbesondere für GasSensoren, nach einem der vorhergehenden Ansprüche, dadurch gekennzeichnet, daß mindestens zwei Keramikpulver mit unterschiedlichen Stabilisatoroxidanteilen, gemischt, in einem nächsten Verfahrensschritt gemeinsam aufgemahlen und anschließend gemeinsam gesintert werden. 8. A method for producing a solid electrolyte ceramic, preferably based on zirconium dioxide for electrochemical applications, in particular for gas sensors, according to one of the preceding claims, characterized in that at least two ceramic powders with different stabilizer oxide fractions are mixed, ground together in a next process step and then sintered together become.
9. Verfahren nach Anspruch 8, dadurch gekennzeichnet, daß koprazipitierte Keramikpulver eingesetzt werden. 9. The method according to claim 8, characterized in that coprecipitated ceramic powder is used.
10. Verwendung einer Festelektrolytkeramik nach einem der Ansprüche 1 bis 7, für Abgassensoren von Brennkraftmaschinen, insbesondere für Lambca-Sonden oder polarographische Sonden. 10. Use of a solid electrolyte ceramic according to one of claims 1 to 7, for exhaust gas sensors of internal combustion engines, in particular for Lambca probes or polarographic probes.
PCT/DE1991/000938 1991-01-04 1991-12-03 Solid ceramic electrolyte for electrochemical purposes, especially for gas sensors, and process for making it WO1992012105A1 (en)

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