Transition metal oxide gas sensor

{
  "publication_number": "US6173602B1",
  "country": "US",
  "kind": "B1",
  "title": "Transition metal oxide gas sensor",
  "abstract": "A sensor and a sensing method for use in a gas or gaseous mixture is provided. The sensor includes a gas sensitive material, MO 3-x, in which M is predominantly or exclusively MO and MO 3-x, is a substoichiometric molybdenum trioxide which exhibits a response in the form of an increase or a decrease in an electrical property of the material in the presence of a gas. The gas sensitive material is in communication with two or more electrodes and is arranged for being contacted with a gas or gaseous mixture. The electrodes are in direct communication with the gas sensitive material by being in contact therewith. The sensor incorporates a temperature sensor. The sensor includes a heating element.",
  "claims": [
    "1. A sensor for detecting gases comprising plural electrodes, a gas sensitive material in contact with each electrode, the gas sensitive material being MO 3-x, wherein M is predominantly or exclusively Mo and MO 3-x is a substoichiometric molybdenum trioxide which includes five-valent transitional metal ions and which exhibits a response in the form of an increase or a decrease in an electrical property of the material in the presence of a gas or gaseous mixture.",
    "2. The sensor as claimed in claim 1, wherein the plural electrodes consist of at least two electrodes in communication with the gas sensitive material and wherein said gas sensitive material and the electrodes are arranged so as to be capable of being contacted with a gas or gaseous mixture.",
    "3. The sensor as claimed in claim 2, wherein the electrodes are in direct communication with the gas sensitive material by being in contact therewith.",
    "4. The sensor as claimed in claim 1, wherein the sensor incorporates a temperature sensing means.",
    "5. The sensor as claimed in claim 1, wherein the sensor includes a heating means.",
    "6. A method for effecting determination in a gas or gaseous mixture which comprises providing a gas sensor with plural electrodes, each electrode in contact with a gas sensitive material having a formula MO 3-x in which M is predominantly or exclusively Mo and MO 3-x is a substoichiometric molybdenum trioxide which includes five-valent transitional metal ions, contacting the sensor with the gas or gaseous mixture and measuring the electrical response of the sensor, contacting each electrode and the gas sensitive material with a gas or gaseous mixture wherein the gas sensitive material as herein before defined exhibiting a response in the form of an increase or a decrease in an electrical property of the material in the presence of the gas or gaseous mixture, detecting the change in the electrical property by the electrodes, measuring the change in electrical property and determining the gas concentration.",
    "7. The method as claimed in claim 6, the plural electrodes further comprising at least two electrodes in communication with the gas sensitive material, and contacting the gas sensitive material and the electrodes with the same gas or gaseous mixture.",
    "8. The method as claimed in claim 6, further comprising providing the gas sensitive material with a porosity and increasing surface area for contact with the gas or gaseous mixture.",
    "9. The method as claimed in claim 6, wherein the measuring further comprises measuring the resistance of the sensor.",
    "10. The method as claimed in claim 6, wherein the measuring further comprises measuring the capacitance of the sensor.",
    "11. The method as claimed claim 6, wherein the measuring further comprises measuring the impedance of the sensor.",
    "12. The method as claimed in claim 6, further comprising detecting hydrogen, ethene, ammonia, propane, methane, carbon monoxide, ozone, chlorine, nitrogen dioxide, sulphur dioxide, or hydrogen sulphide with the sensor.",
    "13. A sensor for detecting gases comprising plural electrodes having first and second portions, a gas sensitive material in contact with portions of each electrode, and a gas or gaseous mixture for contacting the gas sensitive material, wherein the gas sensitive material is MO 3-x, wherein M is predominantly or exclusively Mo and MO 3-x is a substoichiometric molybdenum trioxide exhibiting a change in an electrical property in the presence of the gas or gaseous mixture, wherein a small fraction of the Mo is substituted with metal having a principal valence not greater than six, and wherein the value of x in the gas sensitive material MO 3-x is not greater than 0.3.",
    "14. The sensor of claim 13, wherein the electrodes directly contact the gas sensitive material in said one portions.",
    "15. The sensor of claim 13, further comprising a temperature sensor for sensing a temperature.",
    "16. The sensor of claim 13, further comprising a heater connected to the sensor for heating.",
    "17. A sensor for detecting gases comprising plural electrodes having first and second portions, a gas sensitive material in contact with portions of each electrode, and a gas or gaseous mixture for contacting the gas sensitive material, wherein the gas sensitive material is MO 3-x, wherein M is predominantly or exclusively Mo and MO 3-x is a substoichiometric molybdenum trioxide exhibiting a change in an electrical property in the presence of the gas or gaseous mixture, further comprising metal ions in the gas sensitive material MO 3-x having a valence not greater than six and the value of x is greater than zero.",
    "18. The sensor of claim 17, wherein the metal ions are transition metal ions.",
    "19. The sensor of claim 18, wherein the transition metal is tantalum.",
    "20. A method for sensing gases comprising providing a gas sensor with plural electrodes, partially covering each electrode with a gas sensitive material, contacting each electrode and the gas sensitive material with a gas or gaseous mixture, changing an electrical property of the gas sensitive material in response to the gas or gaseous mixture, detecting the change as an increase or a decrease in the electrical property of the material in the presence of the gas or gaseous mixture by the electrodes, measuring the change in the electrical property and determining the gas concentration, wherein the gas sensitive material has a formula MO 3-x in which M is predominantly or exclusively Mo and MO 3-x is a substoichiometric molybdenum trioxide, wherein a small fraction of the Mo is substituted with metal having a principal valence not greater than six, and wherein the x in the gas sensitive material MO 3-x has a value not greater than 0.3.",
    "21. The method of claim 20, further comprising providing the gas sensitive material with a porous and increased surface area for contacting with the gas or gaseous mixture.",
    "22. The method of claim 20, wherein the measuring further comprises measuring the resistance of the sensor.",
    "23. The method of claim 20, wherein the measuring further comprises measuring the capacitance of the sensor.",
    "24. The method of claim 20, wherein the measuring further comprises measuring the impedance of the sensor.",
    "25. The method of claim 20, wherein the detecting comprises detecting hydrogen, ethene, ammonia, propane, methane, carbon monoxide, or hydrogen sulphide with the sensor.",
    "26. A method for sensing gases comprising providing a gas sensor with Plural electrodes, partially covering each electrode with a gas sensitive material, contacting each electrode and the gas sensitive material with a gas or gaseous mixture, changing an electrical property of the gas sensitive material in response to the gas or gaseous mixture, detecting the change as an increase or a decrease in the electrical property of the material the presence of the gas or gaseous mixture by the electrodes, measuring the change in the electrical property and determining the gas concentration, wherein the gas sensitive material has a formula MO 3-x in which M is predominantly or exclusively Mo and MO 3-x is a substoichiometric molybdenum trioxide, wherein a small fraction of the Mo is substituted with metal having a principal valence not greater than six and the value of x is greater than zero.",
    "27. A gas sensor comprising plural electrodes having first and second portions, a gas sensitive material covering one portion of each electrode, wherein the gas sensitive material is responsive to gas and not to changes in relative humidity, and a gas or gaseous mixture for contacting the electrodes and the gas sensitive material, wherein the gas sensitive material is MO 3-x, wherein M is predominantly or exclusively Mo and MO 3-x is a substoichiometric molybdenum trioxide exhibiting a change in an electrical property in the presence of the gas or gaseous mixture, wherein a small fraction of the Mo is substituted with metal having a principal valence not greater than six, and wherein the value of x in the gas sensitive material MO 3-x is not greater than 0.3.",
    "28. A gas sensor comprising plural electrodes having first and second portions, a gas sensitive material covering one portion of each electrode, wherein the gas sensitive material is responsive to gas and not to changes in relative humidity, and a gas or gaseous mixture for contacting the electrodes and the gas sensitive material, wherein the gas sensitive material is MO 3-x, wherein M is predominantly or exclusively Mo and MO 3-x is a substoichiometric molybdenum trioxide exhibiting a change in an electrical property in the presence of the gas or gaseous mixture, further comprising metal ions in the gas sensitive material MO 3-x having a valence not greater than six and the value of x is greater than zero.",
    "29. The sensor of claim 28, wherein the metal ions are of transition metal ions."
  ],
  "cpc": [
    "G01N 27/125"
  ],
  "filing_date": "1998-08-11",
  "publication_date": "2001-01-16",
  "grant_date": "2001-01-16",
  "priority_date": "1998-08-11",
  "application_number": "US-13221698-A",
  "family_id": "22453008",
  "citations": [
    "EP0046989A2",
    "JPH02263146A",
    "JPH0359450A",
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  ]
}