GB2104666A - Solid state oxygen sensor - Google Patents

Solid state oxygen sensor Download PDF

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Publication number
GB2104666A
GB2104666A GB08222998A GB8222998A GB2104666A GB 2104666 A GB2104666 A GB 2104666A GB 08222998 A GB08222998 A GB 08222998A GB 8222998 A GB8222998 A GB 8222998A GB 2104666 A GB2104666 A GB 2104666A
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United Kingdom
Prior art keywords
solid state
oxygen
oxides
oxygen sensor
state oxygen
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Application number
GB08222998A
Inventor
Livio Manes
Fernando Toci
Claudio Maria Mari
Sergio Pizzini
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European Atomic Energy Community Euratom
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European Atomic Energy Community Euratom
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Publication of GB2104666A publication Critical patent/GB2104666A/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
    • G01N27/4075—Composition or fabrication of the electrodes and coatings thereon, e.g. catalysts

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  • Chemical & Material Sciences (AREA)
  • Life Sciences & Earth Sciences (AREA)
  • Health & Medical Sciences (AREA)
  • Physics & Mathematics (AREA)
  • Chemical Kinetics & Catalysis (AREA)
  • Electrochemistry (AREA)
  • Molecular Biology (AREA)
  • Analytical Chemistry (AREA)
  • Biochemistry (AREA)
  • General Health & Medical Sciences (AREA)
  • General Physics & Mathematics (AREA)
  • Immunology (AREA)
  • Pathology (AREA)
  • Measuring Oxygen Concentration In Cells (AREA)

Abstract

A solid state oxygen sensor for measuring partial pressures of oxygen, which sensor is constituted by an electrolyte cell (1) whose oxygen- sensitive measuring electrodes (3) is one or more non-stochiometric oxides, the electrolyte being a solid state ceramic. The oxides may have mixed conductivity, both ionic and electronic and may be either non stoichiometric oxides alone or mixtures of such oxides. <IMAGE>

Description

SPECIFICATION Solid state oxygen sensor The present invention relates to solid state electrochemical devices for measuring oxygen activity, which devices include a solid oxide electrolyte and oxides as the oxygen sensitive electrodic material.
Electrochemical cells are known in the art for the measurement of the partial pressure of oxygen, which are constituted by a solid oxide electrolyte having as its electrodes unoxidisable electronic conductors, for example consisting of one of the noble metals, particularly: Pt.
The solid electrolyte is a ceramic oxide or a vitreous phase with pure ionic conduction, for example, a solid solution of oxides defective in oxygen ions.
Said cells, hereinafter called "oxygen sensors" have various drawbacks principally due to the metallic electrodic material (Pt), which considerably limits their possibilities of use.
In fact, the oxygen partial pressures measured are inferior to real values, when in the gas mixtures to be analysed there are present traces of oxidisable substances, such as H2, CO, SO2 and hydrocarbons.
When measuring the oxygen activity in CO/CO2 mixtures, one observes a good precision in determining the ratio of the two gases, but the response times are very high for fast changes in the gas mixture composition.
When SOx (x=2 or 3) is present in the gases to be analysed, the response times are very high.
Many metals may poison said electrode material (Pt) and the utilisation of the oxygen sensor in the control of the reducing atmosphere in metal-lurgical application, sometimes, is very critical or impossible.
Particularly, the electrode material (Pt) is easily poisoned by Pb; for this reason the use of such a device for the control of exhaust emission from an engine fed with gasoline containing Pborganometallic compounds is excluded.
For obviating the said defects and for producing an electrochemical solid state oxygen sensor capable of being used in a wider range of application, we propose, according to the present invention, a new solid state electrochemical device in which the electrodic material (generally an unoxidisable electronic conductor, such as a noble metal) is constituted by oxide materials with mixed ionic and electronic electrical conductivity.
Such materials are either non-stoichiometric oxides (PrO2 TbO,, or mixtures of said oxides e.g.: Tb 2-x+Ce 2~x; PrO2~x+CeO2~x) or mixed oxides (LaCrO3; La1~xSrxCrO3 and so on).
The present invention will now be described, by way of example, with reference to the accompanying drawing, which shows the embodiment of the sensor of the present invention taken in longitudinal cross-section.
In Figure 1 is shown a container 1 made of a ceramic material, constituting the solid electrolyte, with its internal wall 2 and/or external wall 3 being in contact with an oxide (oxygen sensitive electrode).
The internal reference compartment uses a chemical system consisting of either a gaseous mixture (e.g. pure 02, air, an oxygen gas mixture, CO/CO2 or H2/H20 mixtures) or a metal-oxide mixture, e.g.: Ni, NiO, Fe-FeO etc. for fixing a known oxygen partial pressure.
The internal reference compartment uses as its oxygen sensitive electrode either a noble metal or an oxide.
The external electrode is placed in the gas atmosphere to be analysed and its oxygen sensitive material is either an oxide or a mixture of oxides.
Under operational conditions, an e.m.f. is observed between the said electrodes 2 and 3 as schematized in Fig. 1. It is the value of this e.m.f.
which gives the measure of the oxygen activity.
The device according to the present invention may be industrially empioyed in the following fields: a) atmosphere control in the thermal treating of metals; b) combustion control in steam generators, furnaces and boilers; c) control of the exhaust gases from internal combustion engines; and d) to improve the combustible economy and antipollution device.
Claims
1. A solid state oxygen sensor for measuring partial pressures of oxygen, which sensor is constituted by an electrolyte cell whose oxygensensitive electrodes are non-stoichiometric oxides, the electrolyte being a solid state ceramic.
2. A solid state oxygen sensor as claimed in claim 1 wherein the oxygen-sensitive electrodes are oxides with mixed conductivity, ionic and electronic.
3. A solid state oxygen sensor as claimed in claim 1 wherein the oxygen-sensitive electrodes are oxides containing the potential poisoning metal present in the gas atmosphere to be analysed.
4. A solid state oxygen sensor as claimed in claim 1 wherein the oxygen sensitive electrodes are mixed oxides containing two or more cations.
5. A solid state oxygen sensor as claimed in claim 1 wherein the oxygen sensitive electrodes are mixtures of oxides.
6. A solid state oxygen sensor as claimed in claim 1 wherein the cell is formed by a solid state ceramic container having one wall in contact with the oxides which constitute the oxygensensitive electrode.
7. A solid state oxygen sensor as claimed in claim 1 wherein the cell is formed by a solid state ceramic container having both walls in contact with the oxides constituting the oxygen-sensitive electrodes.
8. A solid state oxygen sensor as claimed in claims 1 to 5 wherein the cell has one wall in
**WARNING** end of DESC field may overlap start of CLMS **.

Claims (20)

**WARNING** start of CLMS field may overlap end of DESC **. SPECIFICATION Solid state oxygen sensor The present invention relates to solid state electrochemical devices for measuring oxygen activity, which devices include a solid oxide electrolyte and oxides as the oxygen sensitive electrodic material. Electrochemical cells are known in the art for the measurement of the partial pressure of oxygen, which are constituted by a solid oxide electrolyte having as its electrodes unoxidisable electronic conductors, for example consisting of one of the noble metals, particularly: Pt. The solid electrolyte is a ceramic oxide or a vitreous phase with pure ionic conduction, for example, a solid solution of oxides defective in oxygen ions. Said cells, hereinafter called "oxygen sensors" have various drawbacks principally due to the metallic electrodic material (Pt), which considerably limits their possibilities of use. In fact, the oxygen partial pressures measured are inferior to real values, when in the gas mixtures to be analysed there are present traces of oxidisable substances, such as H2, CO, SO2 and hydrocarbons. When measuring the oxygen activity in CO/CO2 mixtures, one observes a good precision in determining the ratio of the two gases, but the response times are very high for fast changes in the gas mixture composition. When SOx (x=2 or 3) is present in the gases to be analysed, the response times are very high. Many metals may poison said electrode material (Pt) and the utilisation of the oxygen sensor in the control of the reducing atmosphere in metal-lurgical application, sometimes, is very critical or impossible. Particularly, the electrode material (Pt) is easily poisoned by Pb; for this reason the use of such a device for the control of exhaust emission from an engine fed with gasoline containing Pborganometallic compounds is excluded. For obviating the said defects and for producing an electrochemical solid state oxygen sensor capable of being used in a wider range of application, we propose, according to the present invention, a new solid state electrochemical device in which the electrodic material (generally an unoxidisable electronic conductor, such as a noble metal) is constituted by oxide materials with mixed ionic and electronic electrical conductivity. Such materials are either non-stoichiometric oxides (PrO2 TbO,, or mixtures of said oxides e.g.: Tb 2-x+Ce 2~x; PrO2~x+CeO2~x) or mixed oxides (LaCrO3; La1~xSrxCrO3 and so on). The present invention will now be described, by way of example, with reference to the accompanying drawing, which shows the embodiment of the sensor of the present invention taken in longitudinal cross-section. In Figure 1 is shown a container 1 made of a ceramic material, constituting the solid electrolyte, with its internal wall 2 and/or external wall 3 being in contact with an oxide (oxygen sensitive electrode). The internal reference compartment uses a chemical system consisting of either a gaseous mixture (e.g. pure 02, air, an oxygen gas mixture, CO/CO2 or H2/H20 mixtures) or a metal-oxide mixture, e.g.: Ni, NiO, Fe-FeO etc. for fixing a known oxygen partial pressure. The internal reference compartment uses as its oxygen sensitive electrode either a noble metal or an oxide. The external electrode is placed in the gas atmosphere to be analysed and its oxygen sensitive material is either an oxide or a mixture of oxides. Under operational conditions, an e.m.f. is observed between the said electrodes 2 and 3 as schematized in Fig. 1. It is the value of this e.m.f. which gives the measure of the oxygen activity. The device according to the present invention may be industrially empioyed in the following fields: a) atmosphere control in the thermal treating of metals; b) combustion control in steam generators, furnaces and boilers; c) control of the exhaust gases from internal combustion engines; and d) to improve the combustible economy and antipollution device. Claims
1. A solid state oxygen sensor for measuring partial pressures of oxygen, which sensor is constituted by an electrolyte cell whose oxygensensitive electrodes are non-stoichiometric oxides, the electrolyte being a solid state ceramic.
2. A solid state oxygen sensor as claimed in claim 1 wherein the oxygen-sensitive electrodes are oxides with mixed conductivity, ionic and electronic.
3. A solid state oxygen sensor as claimed in claim 1 wherein the oxygen-sensitive electrodes are oxides containing the potential poisoning metal present in the gas atmosphere to be analysed.
4. A solid state oxygen sensor as claimed in claim 1 wherein the oxygen sensitive electrodes are mixed oxides containing two or more cations.
5. A solid state oxygen sensor as claimed in claim 1 wherein the oxygen sensitive electrodes are mixtures of oxides.
6. A solid state oxygen sensor as claimed in claim 1 wherein the cell is formed by a solid state ceramic container having one wall in contact with the oxides which constitute the oxygensensitive electrode.
7. A solid state oxygen sensor as claimed in claim 1 wherein the cell is formed by a solid state ceramic container having both walls in contact with the oxides constituting the oxygen-sensitive electrodes.
8. A solid state oxygen sensor as claimed in claims 1 to 5 wherein the cell has one wall in contact with mixtures of the oxides constituting the oxygen-sensitive electrode.
9. A solid state oxygen sensor as claimed in any one of claims 1 to 5 wherein the cell has both walls in contact with mixtures of the oxides.
10. A solid state oxygen sensor as claimed in any one of claims 1 to 4 wherein the outer wall surfaec of the cell is coated with Pr 2-X'
11. A solid state oxygen sensor as claimed in any one of claims 1 to 4 wherein the outer wall surface of the cell is coated with TbO2~X.
12. A solid state oxygen sensor as claimed in any one of claims 1, 2 or 6 wherein the outer surface is coated with TbO,,+ and/or PrO,,+CeO,~,.
13. A solid state oxygen sensor as claimed in any one of claims 1, 2 or 4 wherein the outer surface is coated with oxides of lantanides.
14. A solid state oxygen sensor as claimed in any one of claims 1, 2 or 6 wherein the outer surface is coated with mixed oxides of lantanides and/or transition metals.
1 5. A solid state oxygen sensor as claimed in any one of claims 1, 2 or 6 wherein the outer surface of the solid electrolyte is coated with mixed oxides of at least one of lantanides, transition and alkaline metals.
1 6. A solid state oxygen sensor as claimed in any one of claims 1, 2 or 6 wherein the outer surface is coated with mixed oxides of at least one of lantanides, transition and alkaline earth metals.
1 7. A solid state oxygen sensor as claimed in any one of claims 1, 2 or 6 wherein the outer surface of the solid electrolyte is coated with mixed oxides of at least one of lantanides, transition, alkaline earth metals.
1 8. A solid state oxygen sensor as claimed in any one of claims 1, 2 or 6 wherein the cell is formed by a solid state ceramic container having one wall in contact with a noble metal and the other wall in contact with the oxides of the preceding claims.
1 9. A solid state oxygen sensor as claimed in any one of claims 1, 2 or 6 having one or both walls in contact with mixtures singles or complex of a material claimed in the preceding claims.
20. A solid state oxygen sensor for measuring partial pressures of oxygen substantially as hereinbefore described with reference to and as illustrated in the accompanying drawings.
GB08222998A 1981-08-10 1982-08-10 Solid state oxygen sensor Withdrawn GB2104666A (en)

Applications Claiming Priority (1)

Application Number Priority Date Filing Date Title
GB8124416 1981-08-10

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GB2104666A true GB2104666A (en) 1983-03-09

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GB08222998A Withdrawn GB2104666A (en) 1981-08-10 1982-08-10 Solid state oxygen sensor

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BE (1) BE894044A (en)
DE (1) DE3229931A1 (en)
FR (1) FR2511154A1 (en)
GB (1) GB2104666A (en)
IT (1) IT1149039B (en)
LU (1) LU84328A1 (en)

Cited By (3)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
GB2147368A (en) * 1983-09-28 1985-05-09 Presswell Engineering Limited Hydraulic apparatus
AU637147B2 (en) * 1989-09-25 1993-05-20 Europaische Wirtschaftsgemeinschaft (E.W.G.) Solid-state oxygen sensor
US7527717B2 (en) * 2002-06-28 2009-05-05 Rosemount Analytical, Inc. Sulfur resistant sensors

Families Citing this family (2)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
AU2828897A (en) * 1996-05-07 1997-11-26 Sri International Solid state electrochemical cell for measuring components of a gas mixture, and related measurement method
US7153412B2 (en) * 2001-12-28 2006-12-26 Kabushiki Kaisha Toyota Chuo Kenkyusho Electrodes, electrochemical elements, gas sensors, and gas measurement methods

Family Cites Families (13)

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Publication number Priority date Publication date Assignee Title
US4021326A (en) * 1972-06-02 1977-05-03 Robert Bosch G.M.B.H. Electro-chemical sensor
FR2196293B1 (en) * 1972-08-18 1975-03-07 Armand Michel
US3932246A (en) * 1973-08-31 1976-01-13 Ford Motor Company Gas sensor and method of manufacture
US4173518A (en) * 1974-10-23 1979-11-06 Sumitomo Aluminum Smelting Company, Limited Electrodes for aluminum reduction cells
US3914169A (en) * 1974-11-25 1975-10-21 Du Pont Oxygen detector having a platinum electrode on a zirconia electrolyte
US3989614A (en) * 1975-01-08 1976-11-02 Tseng Ying Tien Gas sensor
US4097911A (en) * 1975-10-06 1978-06-27 Erie Technological Products, Inc. Base metal electrode capacitor and method of making the same
DE2738756A1 (en) * 1977-08-27 1979-03-01 Bbc Brown Boveri & Cie Electrochemical cell for determining oxygen in exhaust gas - using reference electrode coated with metal oxide catalyst layer
BR7902625A (en) * 1978-05-04 1979-11-27 Du Pont IMPROVEMENT IN OXYGEN CONCENTRATION SENSOR
EP0006989B1 (en) * 1978-06-12 1983-06-15 Corning Glass Works Hot gas measuring device
US4241378A (en) * 1978-06-12 1980-12-23 Erie Technological Products, Inc. Base metal electrode capacitor and method of making the same
DE2837118C2 (en) * 1978-08-25 1982-05-19 Dornier System Gmbh, 7990 Friedrichshafen Porous oxide electrodes for high temperature electrochemical cells
DE2913633C2 (en) * 1979-04-05 1986-01-23 Robert Bosch Gmbh, 7000 Stuttgart Electrochemical measuring sensor for the determination of the oxygen content in gases, in particular in exhaust gases from internal combustion engines, as well as a method for producing the same

Cited By (3)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
GB2147368A (en) * 1983-09-28 1985-05-09 Presswell Engineering Limited Hydraulic apparatus
AU637147B2 (en) * 1989-09-25 1993-05-20 Europaische Wirtschaftsgemeinschaft (E.W.G.) Solid-state oxygen sensor
US7527717B2 (en) * 2002-06-28 2009-05-05 Rosemount Analytical, Inc. Sulfur resistant sensors

Also Published As

Publication number Publication date
DE3229931C2 (en) 1991-12-12
FR2511154B1 (en) 1985-02-15
LU84328A1 (en) 1983-02-28
IT8248946A0 (en) 1982-08-05
DE3229931A1 (en) 1983-02-17
FR2511154A1 (en) 1983-02-11
BE894044A (en) 1982-12-01
IT1149039B (en) 1986-12-03

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