# US 12,222,314 B2 · Sensor element of NOx sensor

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- Number: US 12,222,314 B2
- Document ID: US12222314B2
- Status: Granted
- Kind: B2
- Application number: 17/577,426
- Filed: 2022-01-18
- Published: 2022-07-28
- Granted: 2025-02-11
- Earliest claimed: 2021-01-22
- Assignees: NGK Insulators, Ltd.
- Applicants: NGK Insulators, Ltd.
- Inventors: Takayuki Sekiya; Yusuke Watanabe; Shiho Iwai
- Web page: https://patentgrep.com/patent/US12222314B2

## CPC

- G01N 27/409: Oxygen concentration cells
- G01N 27/406: Cells and probes with solid electrolytes
- G01N 27/4071: {using sensor elements of laminated structure}
- G01N 27/4074: {for detection of gases other than oxygen}
- G01N 27/4075: {Composition or fabrication of the electrodes and coatings thereon, e.g. catalysts}
- G01N 27/4077: {Means for protecting the electrolyte or the electrodes}
- G01N 27/41: Oxygen pumping cells
- G01N 27/417: using cells {, i.e. more than one cell} and probes with solid electrolytes
- G01N 33/0037: {NOx}
- 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)

## Abstract

A sensor element includes: a base part containing an oxygen-ion conductive solid electrolyte as a constituent material; at least one internal space into which a measurement gas is introduced; and at least one pump cell including an internal electrode disposed to face the internal space, an out-of-space pump electrode disposed at a location other than the internal space, and a portion of the base part located between these electrodes, the internal electrode includes a noble metal, the solid electrolyte, and a pore, and, in the internal electrode, a degree of variation of a boundary of a first region formed of the base part or the solid electrolyte contiguous with the base part and a second region occupied by the noble metal and the pore in a thickness direction of the element is 0.5 μm or more and 6.5 μm or less.

## Claims

### Claim 1

A sensor element of a limiting current type NOx sensor, the sensor element comprising:
a base part containing an oxygen-ion conductive solid electrolyte as a constituent material;
a measurement internal space into which a measurement gas having an oxygen concentration adjusted in advance is introduced; and
at least one pump cell including a measurement electrode disposed in the measurement internal space, an out-of-space pump electrode disposed at a location other than the measurement internal space, and a portion of the base part located between the measurement electrode and the out-of-space pump electrode, wherein
the measurement electrode includes a noble metal, the oxygen-ion conductive solid electrolyte material, and pores, and includes:
an upper layer consisting of the noble metal, the oxygen-ion conductive solid electrolyte material, and the pores; and
a lower layer consisting of the noble metal and the oxygen-ion conductive solid electrolyte material,
in the measurement electrode, a region boundary variation degree being a degree of variation of a boundary between a first region and a second region in a thickness direction of the sensor element is 0.5 μm or more and 6.5 μm or less, the first region being formed of the base part and the oxygen-ion conductive solid electrolyte material contiguous with the base part, the second region being occupied by the noble metal and the pores,
a volume ratio of the oxygen-ion conductive solid electrolyte material in the upper layer is 20% to 40%, and
a volume ratio of the oxygen-ion conductive solid electrolyte material in the lower layer is 50% to 60%.

### Claim 2 (depends on 1)

The sensor element of the NOx sensor according to claim 1, wherein
a ratio of a thickness of the upper layer to a thickness of the lower layer is in a range of 95:5 to 10:90.

### Claim 3 (depends on 2)

The sensor element of the NOx sensor according to claim 2, wherein
the ratio of the thickness of the upper layer to the thickness of the lower layer is in a range of 90:10 to 30:70.

### Claim 4 (depends on 3)

The sensor element of the NOx sensor according to claim 3, wherein
the region boundary variation degree is 1 μm or more and 5 μm or less.

### Claim 5 (depends on 2)

The sensor element of the NOx sensor according to claim 2, wherein the region boundary variation degree is 1 μm or more and 5 μm or less.

### Claim 6 (depends on 1)

The sensor element of the NOx sensor according to claim 1, wherein
the region boundary variation degree is 1 μm or more and 5 μm or less.