Sintered electrically conductive oxide for oxygen sensor electrode, and oxygen sensor using the same

Patent metadata

Field	Value
Publication number	US-10883192-B2
Application number	US-201615152888-A
Country	US
Kind code	B2
Filing date	May 12, 2016
Priority date	May 13, 2015
Publication date	Jan 5, 2021
Grant date	Jan 5, 2021

Abstract

A sintered electrically conductive oxide for an oxygen sensor electrode includes a crystal phase formed of a perovskite-type electrically conductive oxide containing at least La, Fe and Ni. The oxide has an absolute value of thermoelectromotive force at 770° C. of 21.0 μV/K or less.

First claim

What is claimed is:

1. An oxygen sensor for measuring a concentration of a gas to be measured, the oxygen sensor comprising:
a closed-bottomed tubular substrate formed of ceramic and extending in a longitudinal direction;
an external electrode formed of a noble metal and disposed on an outer surface of the substrate; and
a reference electrode disposed on an inner surface of the substrate,
wherein
the reference electrode is an electrically conductive layer formed of a sintered electrically conductive oxide,
the sintered electrically conductive oxide comprises a crystal phase formed of a perovskite-type electrically conductive oxide having a crystal structure expressed by following formula (1):
La a Co b Fe c Ni d O x   (1),

wherein, in formula (1):
a+b+c+d= 1,
1.25≤ x≤ 1.75,

0.474≤ a≤ 0.512,

0≤ b≤ 0.225,

0< c≤ 0.300,and
0.2005≤ d≤ 50.350; and

the sintered electrically conductive oxide has an absolute value of thermoelectromotive force at 770° C. of 21.0 μV/K or less.

2. The oxygen sensor as claimed in claim 1 , wherein, in formula (1):
0.474≤ a< 0.512.

3. The oxygen sensor as claimed in claim 1 , wherein the sintered electrically conductive oxide contains substantially no alkaline earth metal elements.

4. The oxygen sensor as claimed in claim 1 , wherein the external electrode is configured for contact with the gas to be measured, and the reference electrode is configured for contact with a gas serving as a reference for detecting the oxygen concentration of the gas to be measured.

5. The oxygen sensor as claimed in claim 1 , wherein the reference electrode has a length in the longitudinal direction from 1 cm to 10 cm.

6. The oxygen sensor as claimed in claim 1 , wherein the substrate is formed of zirconia doped with yttria.

7. The oxygen sensor as claimed in claim 1 , wherein the crystal phase formed of the perovskite-type electrically conductive oxide has the crystal structure expressed by following formula (2):
La a Fe c Ni d O x   (2),

wherein, in formula (2):
a+c+d= 1,
1.25≤ x≤ 1.75,

0.474≤ a≤ 0.512,

0< c≤ 0.300,and
0.200≤ d≤ 0.350.

8. The oxygen sensor as claimed in claim 1 , wherein a and b satisfy
0.474≤ a< 0.512, and

0≤ b< 0.100.

9. The oxygen sensor as claimed in claim 1 , wherein b satisfies
0< b< 0.100.

Assignees

• Ngk Spark Plug Co

Inventors

• Kozuka Hisashi
• Okimura Yasuyuki
• Ohbayashi Kazushige

Classifications

• G01N27/125 Primary

  Composition of the body, e.g. the composition of its sensitive layer · CPC title

• C04B35/62625

  Wet mixtures · CPC title

• C04B2235/3275

  Cobalt oxides, cobaltates or cobaltites or oxide forming salts thereof, e.g. bismuth cobaltate, zinc cobaltite · CPC title

• C04B35/632

  Organic additives · CPC title

• C04B35/50

  based on rare-earth compounds {(non-oxide rare earth compounds C04B35/5156)} · CPC title