US 12,222,314 B2
Sensor element of NOx sensor
Takayuki Sekiya, Nisshin (JP); Yusuke Watanabe, Nagoya (JP); and Shiho Iwai, Nagoya (JP)
Assigned to NGK INSULATORS, LTD., Nagoya (JP)
Filed by NGK Insulators, Ltd., Nagoya (JP)
Filed on Jan. 18, 2022, as Appl. No. 17/577,426.
Claims priority of application No. 2021-008725 (JP), filed on Jan. 22, 2021; and application No. 2022-002293 (JP), filed on Jan. 11, 2022.
Prior Publication US 2022/0236212 A1, Jul. 28, 2022
Int. Cl. G01N 27/41 (2006.01); G01N 27/406 (2006.01); G01N 27/407 (2006.01); G01N 27/409 (2006.01); G01N 27/417 (2006.01); G01N 33/00 (2006.01)
CPC G01N 27/409 (2013.01) [G01N 27/406 (2013.01); G01N 27/4071 (2013.01); G01N 27/4074 (2013.01); G01N 27/4075 (2013.01); G01N 27/4077 (2013.01); G01N 27/41 (2013.01); G01N 27/417 (2013.01); G01N 33/0037 (2013.01)] 6 Claims
OG exemplary drawing
 
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%.