Sensor electrode, manufacturing method thereof, and metal paste for electrode formation

Patent metadata

Field	Value
Publication number	US-9784709-B2
Application number	US-201314430235-A
Country	US
Kind code	B2
Filing date	Sep 17, 2013
Priority date	Sep 25, 2012
Publication date	Oct 10, 2017
Grant date	Oct 10, 2017

Abstract

The present invention relates to a gas sensor electrode including a conductive particle phase made of Pt or Pt alloy and a ceramic particle phase being mixed and dispersed, wherein a rate of content of the ceramic particle phase is 6.0 to 22.0 mass %, and a void ratio is 2.5 to 10.0%, and a dispersion degree of the conductive particle phase per length of 25 μm on the electrode surface is 0.60 to 0.85 μm, and a dispersion degree of the conductive particle phase in the electrode cross section per length of 100 μm in a direction parallel to the electrode surface is 2.0 to 4.0 μm. This electrode can be produced by firing a metal paste made by dispersing, in a solvent, a conductive particle having a core/shell structure in which a core particle such as Pt is covered with a ceramic shell and ceramic powder. The gas sensor electrode according to the present invention has a high electrode activity.

First claim

The invention claimed is:

1. A metal paste for forming a gas sensor electrode, in which (1) a conductive particle having a core/shell structure comprising a core particle made of Pt or Pt alloy and a shell made of ceramic covering at least a portion of the core particle, and (2) ceramic powder, are dispersed in a solvent,
wherein the conductive particle is a particle of which average particle diameter is 90 to 500 nm, and the core particle is covered with ceramic of 0.5 to 3.0 mass % with respect to the mass of the conductive particle,
a content of the ceramic powder is 5 to 20 mass % with respect to a total mass of the conductive particle and the ceramic powder,
a total content of a ceramic component in a metal paste is 6.0 to 22.0 mass % with respect to the total mass of the conductive particle and the ceramic powder, and
further, a dispersion degree measured according to a line transect method based on a grind gauge is equal to or less than 15 μm.

2. The metal paste for forming the gas sensor electrode according to claim 1 , wherein the particle diameter of the ceramic powder is 100 to 500 nm.

3. The metal paste for forming the gas sensor electrode according to claim 2 , wherein the ceramic acting as the shell and the ceramic powder comprise ceramic including ZrO 2 .

4. The metal paste for forming the gas sensor electrode according to claim 2 , wherein the core particle comprises any of Pt or Pt—Pd alloy including Pd of 30 mass % or less.

5. A manufacturing method for a gas sensor electrode, wherein the metal paste for forming the gas sensor electrode according to claim 2 is applied to a substrate, and is fired at 1300 to 1600° C.

6. The metal paste for forming the gas sensor electrode according to claim 1 , wherein the ceramic acting as the shell and the ceramic powder comprise ceramic including ZrO 2 .

7. The metal paste for forming the gas sensor electrode according to claim 6 , wherein the core particle comprises any of Pt or Pt—Pd alloy including Pd of 30 mass % or less.

8. A manufacturing method for the metal paste for forming the gas sensor electrode according to claim 6 , comprising the steps of:
making mixed powder by mixing a composite particle having a core/shell structure made of a precious metal particle made of Pt or Pt alloy and a shell made of ceramic covering at least a portion of the core particle and ceramic powder;
heating the mixed powder to 700 to 1200° C., adjusting a particle diameter of the composite particle, and forming the conductive particles having the core/shell structure of which average particle diameter is 90 to 500 nm; and
dispersing the mixed powder having been subjected to the thermal treatment into a solvent.

9. A manufacturing method for a gas sensor electrode, wherein the metal paste for forming the gas sensor electrode according to claim 6 is applied to a substrate, and is fired at 1300 to 1600° C.

10. The metal paste for forming the gas sensor electrode according to claim 1 , wherein the core particle comprises any of Pt or Pt—Pd alloy including Pd of 30 mass % or less.

11. A manufacturing method for the metal paste for forming the gas sensor electrode according to claim 10 , comprising the steps of:
making mixed powder by mixing a composite particle having a core/shell structure made of a precious metal particle made of Pt or Pt alloy and a shell made of ceramic covering at least a portion of the core particle and ceramic powder;
heating the mixed powder to 700 to 1200° C., adjusting a particle diameter of the composite particle, and forming the conductive particles having the core/shell structure of which average particle diameter is 90 to 500 nm; and
dispersing the mixed powder having been subjected to the thermal treatment into a solvent.

12. A manufacturing method for a gas sensor electrode, wherein the metal paste for forming the gas sensor electrode according to claim 1 is applied to a substrate, and is fired at 1300 to 1600° C.

13. A manufacturing method for the metal paste for forming the gas sensor electrode according to claim 1 , comprising the steps of:
making mixed powder by mixing a composite particle having a core/shell structure made of a precious metal particle made of Pt or Pt alloy and a shell made of ceramic covering at least a portion of the core particle and ceramic powder;
heating the mixed powder to 700 to 1200° C., adjusting a particle diameter of the composite particle, and forming the conductive particles having the core/shell structure of which average particle diameter is 90 to 500 nm; and
dispersing the mixed powder having been subjected to the thermal treatment into a solvent.

14. The manufacturing method for the metal paste according to claim 13 , wherein the average particle diameter of the composite particle is 10 to 25 nm.

15. A manufacturing method for the metal paste for forming the gas sensor electrode according to claim 2 , comprising the steps of:
making mixed powder by mixing a composite particle having a core/shell structure made of a precious metal particle made of Pt or Pt alloy and a shell made of ceramic covering at least a portion of the core particle and ceramic powder;
heating the mixed powder to 700 to 1200° C., adjusting a particle diameter of the composite particle, and forming the conductive particles having the core/shell structure of which average particle diameter is 90 to 500 nm; and
dispersing the mixed powder having been subjected to the thermal treatment into a solvent.

Assignees

• Tanaka Precious Metal Ind

Inventors

• Okamoto Nobuhisa
• Hosoi Takuya
• Sakairi Koichi

Classifications

• H01B1/22

  the conductive material comprising metals or alloys · CPC title

• C09D5/24

  Electrically-conducting paints {(conductive materials H01B1/00)} · CPC title

• H01B13/0016

  for heat treatment · CPC title

• G01N27/4075 Primary

  Composition or fabrication of the electrodes and coatings thereon, e.g. catalysts · CPC title

• G01N27/304

  Gas permeable electrodes · CPC title