# US 8,465,636 B2 · Ammonium gas sensor

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- Number: US 8,465,636 B2
- Document ID: US8465636B2
- Status: Granted
- Kind: B2
- Application number: 12/390,567
- Filed: 2009-02-23
- Published: 2009-08-27
- Granted: 2013-06-18
- Earliest claimed: 2008-02-22
- Assignees: Ngk Spark Plug Co., Ltd.
- Applicants: Satoshi Sugaya; Shiro Kakimoto; Hiroyuki Nishiyama; Wataru Matsutani
- Inventors: Satoshi Sugaya; Shiro Kakimoto; Hiroyuki Nishiyama; Wataru Matsutani
- Web page: https://patentgrep.com/patent/US8465636B2

## CPC

- G01N 27/4077: {Means for protecting the electrolyte or the electrodes}
- G01N 27/4075: {Composition or fabrication of the electrodes and coatings thereon, e.g. catalysts}
- G01N 33/0054: {Ammonia}
- Y02A 50/20: Air quality improvement or preservation, e.g. vehicle emission control or emission reduction by using catalytic converters
- G01N: INVESTIGATING OR ANALYSING MATERIALS BY DETERMINING THEIR CHEMICAL OR PHYSICAL PROPERTIES (measuring or testing apparatus or processes other than immunoassay, involving enzymes or microorganisms C12M, C12Q)
- Y02A: TECHNOLOGIES FOR ADAPTATION TO CLIMATE CHANGE

## Abstract

An ammonium gas sensor is provided. The ammonium gas sensor includes: a solid electrolyte layer having oxygen ion conductivity; a detection electrode formed on one surface of the solid electrolyte layer; a reference electrode that is a counter electrode of the detection electrode; a selective reaction layer covering the detection electrode; and a protection layer covering the selective reaction layer and made from a porous material; wherein the detection electrode includes a noble metal as a main component; the selective reaction layer includes oxide represented by AxMyOz as a main component, where A is one or more kind(s) of metal, M is vanadium, tungsten, or molybdenum and x, y, z are atomic ratios; and the protection layer includes the oxide that is in an amount smaller than a content of the oxide included in the selective reaction layer.

## Claims

### Claim 1

An ammonium gas sensor comprising:
a solid electrolyte layer having oxygen ion conductivity;
a detection electrode formed on one surface of the solid electrolyte layer;
a reference electrode that is a counter electrode of the detection electrode;
a selective reaction layer covering the detection electrode; and
a protection layer covering the selective reaction layer and made from a porous material;
wherein
the detection electrode includes a noble metal as a main component;
the selective reaction layer includes an oxide represented by AxMyOz as a main component, where A is one or more kind(s) of metal, M is vanadium, tungsten, or molybdenum and x, y, z are atomic ratios;
the protection layer includes the oxide of the selective reaction layer in an amount smaller than a content of the oxide included in the selective reaction layer, and contains at least one selected from the group consisting of MgAl2O4, SiO2, SiO2/Al2O3, zeolite and SiC as a main component; and
the detection electrode is exposed to the gas to be measured.

### Claim 2 (depends on 1)

The ammonium gas sensor according to claim 1,
wherein
in AxMyOz representing the oxide, A is one or more kind(s) selected from the group consisting of bismuth, lanthanum, strontium, calcium, copper, gadolinium, neodymium, yttrium, samarium, and magnesium.

### Claim 3 (depends on 1)

The ammonium gas sensor according to claim 1,
wherein
the oxide is represented by BiVO4.

### Claim 4 (depends on 1)

The ammonium gas sensor according to claim 1,
wherein
the oxide content in the protection layer in the vicinity of an interface between the protection layer and the selective reaction layer is 10 mol % or less.

### Claim 5 (depends on 1)

The ammonium gas sensor according to claim 1,
wherein
the oxide content in the protection layer is smaller in the vicinity of a surface of the protection layer as compared to that in the vicinity of an interface between the protection layer and the selective reaction layer.

### Claim 6 (depends on 1)

The ammonium gas sensor according to claim 1,
wherein
the oxide content in the protection layer in the vicinity of an interface between the protection layer and the selective reaction layer is 0.1 mol % or more.

### Claim 7 (depends on 1)

The ammonium gas sensor according to claim 1,
wherein
a thickness of a part of the protection layer that includes the oxide content of 0.1 to 10 mol % is equal to or less than a thickness of the selective reaction layer.

### Claim 8 (depends on 1)

The ammonium gas sensor according to claim 1,
wherein
the ammonium gas sensor comprises a second protection layer covering the reference electrode, and
the second protection layer does not contain the oxide included in the selective reaction layer.

### Claim 9 (depends on 1)

The ammonium gas sensor according to claim 1,
wherein
the selective reaction layer comprises at least one of AxOz and MyOz, where A is one or more kind(s) of metal, M is vanadium, tungsten, or molybdenum, and x, y, and z are atomic ratios.