Nitrogen-oxide gas sensor with long signal stability
View Patent ↗The present invention provides a nitrogen-oxide gas sensor that is able to measure nitric oxide and nitrogen dioxide at the same time and ensure measurement accuracy and long stability. For these purposes, the nitrogen-oxide gas sensor includes: an oxide ion conductive solid electrolyte; a primary film that contacts the solid electrolyte and is made of a p-type semi-conductor metal oxide; a secondary film that contacts the solid electrolyte and is made of a p-type semiconductor metal oxide; an n-type semiconductor metal oxide that is included in at least one of the primary and secondary films; a power source that applies electric power to the primary and secondary films by electrically connecting a primary node to the primary film and a secondary node to the secondary film; and a measurement unit that measures the electric potential difference between the primary and secondary nodes.
1. A nitrogen-oxide gas sensor comprising:
an oxide ion conductive solid electrolyte;
a first film that contacts the solid electrolyte and is made of a p-type semiconductor metal oxide;
a second film that contacts the solid electrolyte and is made of a p-type semiconductor metal oxide; an n-type semiconductor metal oxide that is included in at least one of the first and second films; a power source that applies electric power to the first and second films by electrically connecting a first node to the first film and a second node to the second film; and a measurement unit that measures the electric potential difference between the first and second nodes.
2. The nitrogen-oxide gas sensor of claim 1 , wherein the n-type semiconductor metal oxide is formed by mixing the p-type semiconductor metal oxide of at least one of the first and second films.
3. The nitrogen-oxide gas sensor of claim 1 , wherein the n-type semiconductor metal oxide is formed by solid solution treating the p-type semiconductor metal oxide of at least one of the first and second films.
4. The nitrogen-oxide gas sensor of claim 1 , wherein one of the first and second films that comprises the n-type semiconductor metal oxide is formed as a stack body of a film comprising the p-type semiconductor metal oxide and a buffer film comprising the n-type semiconductor metal oxide.
5. The nitrogen-oxide gas sensor of claim 4 , wherein the buffer film is formed as a solid solution of the n-type semiconductor metal oxide and the p-type semiconductor metal oxide.
6. The nitrogen-oxide gas sensor of claim 4 , wherein the buffer film is formed as a mixture of the n-type semiconductor metal oxide and the p-type semiconductor metal oxide.
7. A nitrogen-oxide gas sensor comprising:
an oxide ion conductive solid electrolyte;
a first film that contacts the solid electrolyte and is made of a p-type semiconductor metal oxide;
a second film that contacts the solid electrolyte and is made of a p-type semiconductor metal oxide;
an n-type semiconductor metal oxide that is included in at least one of the first and second films;
a power source that applies electric power to the first and second films by electrically connecting a first node to the first film and a second node to the second film;
a measurement unit that measures the electric potential difference between the first and second nodes; and
a first electrode that is formed on a surface of the first film facing the solid electrolyte and is formed of a conductive metal.
8. The nitrogen-oxide gas sensor of claim 7 , further comprising a third film that contacts the solid electrolyte, is formed of a conductive metal, and is connected to the first film in parallel with respect to the power source.
9. The nitrogen-oxide gas sensor of claim 8 , wherein the first electrode and the third film are integrally formed with each other as a single body.
10. The nitrogen-oxide gas sensor of claim 8 , wherein the first electrode and the third film are each formed of a noble metal.
11. A nitrogen-oxide gas sensor comprising:
an oxide ion conductive solid electrolyte;
a first film that contacts the solid electrolyte and is made of a p-type semiconductor metal oxide;
a second film that contacts the solid electrolyte and is made of a p-type semiconductor metal oxide;
an n-type semiconductor metal oxide that is included in at least one of the first and second films;
a power source that applies electric power to the first and second films by electrically connecting a first node to the first film and a second node to the second film;
a measurement unit that measures the electric potential difference between the first and second nodes; and
a second electrode that is formed on a surface of the second film facing the solid electrolyte and is formed of a conductive metal.
12. The nitrogen-oxide gas sensor of claim 11 , further comprising a fourth film that contacts the solid electrolyte, is formed of a conductive metal, and is connected to the second film in parallel with respect to the power source.
13. The nitrogen-oxide gas sensor of claim 12 , wherein the second electrode and the fourth film are integrally formed with each other as a single body.
14. The nitrogen-oxide gas sensor of claim 12 , wherein the second electrode and the fourth film are each formed of a noble metal.