JPH1172476A5 - - Google Patents

Claims (11)

A nitrogen oxide gas sensor of a type that measures the potential difference between a detection electrode provided on a zirconia solid electrolyte substrate, which is an oxygen ion conductor, and a platinum counter electrode or platinum reference electrode on the solid electrolyte substrate that is insensitive to _NOx and that forms a pair with the detection electrode, wherein the gas detection electrode of the sensor is an alloy electrode made of platinum and rhodium or a cermet electrode made of a platinum-rhodium alloy and zirconia. 2. The nitrogen oxide gas sensor according to claim 1, wherein the detection electrode is an alloy electrode made of platinum and rhodium or a cermet electrode made of platinum, a rhodium alloy and zirconia, and the rhodium content is at least 0.5 wt % based on the total amount of platinum and rhodium. a nitrogen oxide gas sensor having a structure in which a test gas is introduced into a first chamber that receives gas from a gas inlet opening that leads to the test gas atmosphere, or a second chamber that communicates with the first chamber, and which is provided within a pair of sensor substrates made of a zirconia solid electrolyte, which is an oxygen ion conductor; an oxygen exhaust electrode or oxygen intake electrode provided in the first chamber or the second chamber; a means for controlling the oxygen concentration in the first chamber or the second chamber; a detection electrode that detects NO or _NO converted to _NO in the first chamber; and a platinum counter electrode formed in the same chamber as the detection electrode, or a platinum counter electrode formed so as to communicate with a duct that maintains a reference oxygen concentration across the zirconia solid electrolyte substrate that contacts the detection electrode, and the detection electrode is an alloy electrode made of platinum and rhodium, or a cermet electrode made of a platinum-rhodium alloy and zirconia. 4. A nitrogen oxide gas sensor according to claim 3, wherein the oxygen concentration in the chamber in which the detection electrode is formed is controlled so as to generate a _NOx potential difference from a mixed potential of oxygen and _NOx at the detection electrode. A nitrogen oxide gas sensor of a type that measures the potential difference between a detection electrode provided on a zirconia solid electrolyte, which is an oxygen ion conductor, and a Pt reference electrode on the solid electrolyte that is paired with the detection electrode and has no activity toward _NOx , wherein the gas detection electrode of the sensor is an electrode formed by laminating a rhodium layer on a platinum layer, or a cermet electrode formed by dispersing zirconia in the laminated electrode. 6. The nitrogen oxide gas sensor according to claim 5, wherein the rhodium layer of the detection electrode is a vapor-deposited layer. A nitrogen oxide gas sensor that measures the potential difference between a detection electrode provided on a zirconia solid electrolyte, which is an oxygen ion conductor, and a Pt reference electrode on the solid electrolyte that is paired with the detection electrode and has no activity toward _NOx , wherein the gas detection electrode of the sensor is made of an alloy of platinum and rhodium, or an alloy to which a third metal element is added, and the third metal element is at least one of Ru, Ir, Pd, Au, and Ag. A nitrogen oxide gas sensor that measures the potential difference between a detection electrode provided on a zirconia solid electrolyte, which is an oxygen ion conductor, and a Pt reference electrode on the solid electrolyte that is paired with the detection electrode and has no activity toward _NOx , wherein the gas detection electrode of the sensor is made of a mixed phase of platinum and rhodium oxide, or a mixture of platinum and rhodium oxide with at least one oxide of a third metal element, and the third metal element is any of Ru, Ir, Pd, Ag, Ni, and Cr. 9. The nitrogen oxide gas sensor according to claim 7, wherein zirconia is dispersed and added to said detection electrode. 9. The nitrogen oxide gas sensor according to claim 7, wherein the amount of Rh or the third metal element added is such that the ratio (Rh+third element)/(Pt+Rh+third element) is 0.01 to 0.5. A nitrogen oxide gas sensor that measures the potential difference between a detection electrode provided on a zirconia solid electrolyte, which is an oxygen ion conductor, and a Pt reference electrode on the solid electrolyte that is paired with the detection electrode and has no activity toward _NOx , wherein the gas detection electrode of the sensor is an electrode made of iridium, an electrode made of an alloy or mixed phase of iridium and rhodium, or a cermet electrode made by adding zirconia dispersed in the electrode.