Electrochemical measuring cell
AssigneeBrown, Boveri & Cie AG
InventorsFranz-Josef Rohr, Hubert Holick
Life of this patent
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Abstract
An electrochemical measuring cell for determining the oxygen content in exhaust gases from internal-combustion engines and combustions having an ion-conducting solid electrolyte with a measuring electrode as a first layer on the solid electrolyte and a reference electrode as a second layer on the solid electrolyte. A third layer coats the first layer measuring electrode and contains a material with a high partial oxygen pressure to obtain a characteristic U=f(.lambda.) which has a small slope in the range of the air number of about 1; a material with a medium partial oxygen pressure to obtain a characteristic with a medium slope; and a material with low partial oxygen pressure to obtain a characteristic with a steep slope.
Claims15
In an electrochemical measuring cell for determining the oxygen content in gases, particularly in exhaust gases from internal-combustion engines or combustion chambers, having an ion-conducting solid electrolyte for passage of oxygen ions through the solid electrolyte with a measuring electrode disposed as a first layer on a surface of the ion-conducting solid electrolyte and a reference electrode disposed as a second layer on a surface of the ion-conducting solid electrolyte opposite the first layer, the combination therewith of a catalytically active porous third layer coating the first layer measuring electrode, said third layer containing a material with a medium partial oxygen pressure to obtain a change in voltage from the electrochemical measuring cell with change in air number with a characteristic which has a medium slope in the range of the air number of about 1 wherein a medium slope means an approximately linear voltage change of the measuring cell of about 500 mV corresponds to a change of the air number of between 0.1 and 0.5 and wherein the third layer contains a mixture of an inert ceramic material with a material of the formula
- Me.sub.x.sup.I Me.sub.y.sup.II Me.sup.III O.sub.3
- where Me.sup.I is a member selected from the group consisting of lanthanum, gadolinium and praseodymium;
- Me.sup.II is a member selected from the group consisting of strontium, calcium and barium;
- and Me.sup.III is a member selected from the group consisting of manganese, nickel, cobalt and chromium, and x has a value of 0.74 to 0.92, and y has a value of 0.08 to 0.26.
In an electrochemical measuring cell for determining the oxygen content in gases, particularly in exhaust gases from internal-combustion engines or combustion chambers, having an ion-conducting solid electrolyte for passage of oxygen ions through the solid electrolyte with a measuring electrode disposed as a first layer on a surface of the ion-conducting solid electrolyte and a reference electrode disposed as a second layer on a surface of the ion-conducting solid electrolyte opposite the first layer, the combination therewith of a catalytically active porous third layer coating the first layer measuring electrode, said third layer containing a material with a low partial oxygen pressure to obtain a change in voltage from the electrochemical measuring cell with change in air number with a characteristic which has a steep slope in the range of the air number of about 1 wherein a steep slope means an approximately linear voltage change of the measuring cell of about 500 mV corresponds to a change of the air number of about 0.05 to 0.1 and wherein the third layer contains a material of the formula
- La.sub.x Sr.sub.(1-x) Cr.sub.x Ni.sub.(1-x) O.sub.3
- where x has a value of 0.7 to 0.95.
In an electrochemical measuring cell for determining the oxygen content in gases, particularly in exhaust gases from internal-combustion engines or combustion chambers, having an ion-conducting solid electrolyte for passage of oxygen ion through the solid electrolyte with a measuring electrode disposed as a first layer on a surface of the ion-conducting solid electrolyte and a reference electrode disposed as a second layer on a surface of the ion-conducting solid electrolyte opposite the first layer, the combination therewith of a catalytically active porous third layer coating the first layer measuring electrode, said third layer containing a material with a low partial oxygen pressure to obtain a change in voltage from the electrochemical measuring cell with change in air number with a characteristic which has a steep slope in the range of the air number of about 1 wherein a steep slope means an approximately linear voltage change of the measuring cell of about 500 mV corresponds to a change of the air number of about 0.05 to 0.1 and wherein the third layer contains a material of the formula Co Cr.sub.2 O.sub.4.
Dependencies are inferred from the claim text.