Nitrogen oxides detection method, and sensor element for detection of nitrogen oxides
AssigneeOsaka Gas Co., Ltd.
InventorsShuzo Kudo, Katsuki Higaki, Hisao Ohnishi
Life of this patent
Estimating the term…
Abstract
The present invention relates to a nitrogen oxide detecting element. Although there has been a demand for effecting detection of a nitrogen oxide by using a semiconductor type gas sensor, no semiconductor type sensors have existed which can detect the nitrogen oxide with good selectivity against other interfering gases (CO, H2) for an extended period of time with good durability. Then, by causing a gas detecting portion to include an oxide containing more than a predetermined amount of Bi and maintaining this gas detecting portion at a temperature range where its electron-conductivity is exhibited, it has become possible to detect the nitrogen oxide.
Claims19
A method of detecting a nitrogen oxide comprising the steps of:
- preparing a sensor element including a gas detecting portion and a pair of electrodes capable of detecting a change in conductivity of the gas detecting portion resulting from contact thereof with the nitrogen oxide, said gas detecting portion containing a metal oxide which contains 50 at. % or more of bismuth as determined by a conversion by the metallic elements basis and which has the Bi2O3 crystalline structure, the metal oxide having the p-type conductivity at a temperature range from a room temperature to 400° C.;
- exposing said sensor element to a target gas suspected of nitrogen oxide contamination;
- and
- detecting the nitrogen oxide by detecting change in the conductivity of the gas detecting portion while maintaining the gas detection portion at said temperature range from a room temperature to 400° C.
A sensor element for detecting a nitrogen oxide comprising:
- a gas detecting portion containing a metal oxide containing 50 at. % or more of bismuth as determined by a conversion by the metallic elements basis and having Bi2O3 crystalline structure, the metal oxide having the p-type conductivity at a temperature range from a room temperature to 400° C., wherein the gas detecting portion also contains, as an additive other than bismuth, one or more elements selected from the group consisting of metallic elements capable of having a valency not grater than 3;
- electrodes capable of detecting a change in conductivity of the gas detecting portion resulting from contact thereof with the nitrogen oxide, the electrodes being electrically connected with said gas detecting portion;
- and
- heating means capable of maintaining the gas detecting portion at said temperature ranging from a room temperature to 400° C.
Dependencies are inferred from the claim text.