Classifications

• • G—PHYSICS
  • G01—MEASURING; TESTING
  • G01N—INVESTIGATING OR ANALYSING MATERIALS BY DETERMINING THEIR CHEMICAL OR PHYSICAL PROPERTIES
  • G01N27/00—Investigating or analysing materials by the use of electric, electrochemical, or magnetic means
  • G01N27/26—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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• Chemical & Material Sciences (AREA)
• Engineering & Computer Science (AREA)
• Manufacturing & Machinery (AREA)
• Life Sciences & Earth Sciences (AREA)
• Health & Medical Sciences (AREA)
• Ceramic Engineering (AREA)
• Chemical Kinetics & Catalysis (AREA)
• Electrochemistry (AREA)
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• Physics & Mathematics (AREA)
• Sustainable Energy (AREA)
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• General Health & Medical Sciences (AREA)
• General Physics & Mathematics (AREA)
• Immunology (AREA)
• General Chemical & Material Sciences (AREA)
• Composite Materials (AREA)
• Sustainable Development (AREA)
• Materials Engineering (AREA)
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• Organic Chemistry (AREA)
• Compositions Of Oxide Ceramics (AREA)
• Conductive Materials (AREA)

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• 1991
  • 1991-01-04 DE DE4100105A patent/DE4100105A1/de active Granted
  • 1991-12-03 WO PCT/DE1991/000938 patent/WO1992012105A1/de unknown

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