Method of measuring oxygen and process for pretreating a solid electrolyte oxygen gas sensing element

Claim 2

A process for pretreating a solid electrolyte oxygen gas sensor element so as to increase the voltage output under rich gas conditions, shorten the switching response time, and reduce the internal resistance thereof, the sensor element comprising a solid electrolyte body having an inner conductive catalyst electrode on the inner surface, that is to be in contact with a reference gas during operation of the sensor, an outer conductive catalyst electrode coating on the outer surface thereof, that is to be in contact with a gas, the oxygen content of which is to be measured during operation of the sensor, and a porous protective coating over at least a portion of said outer electrode, comprising: (a) heating the sensor element to an elevated temperature in excess of 450° C. and subjecting the outer surface thereof, with said outer conductive catalyst coating, to a nonoxidizing atmosphere; and (b) applying a direct current to the sensor element, with said outer electrode as an anode, while said outer surface is at said elevated temperature and subjected to said nonoxidizing atmosphere, the current density thereof being at least 5 milliamperes per square centimeter of the planar surface of said outer conductive catalyst electrode.

Claim 3

The process for pretreating a solid electrolyte oxygen gas sensor element as defined in claim 1 wherein said sensor element is heated to a temperature in the range of 600°-900° C.

Claim 4

The process for pretreating a solid electrolyte oxygen gas sensor element as defined in claim 1 wherein said nonoxidizing gas is a reducing gas.

Claim 5

The process for pretreating a solid electrolyte oxygen gas sensor element as defined in claim 1 wherein said nonoxidizing gas is a neutral gas.

Claim 6

The process for pretreating a solid electrolyte oxygen gas sensor element as defined in claim 4 wherein said neutral gas comprises nitrogen.

Claim 7

The process for pretreating a solid electrolyte oxygen gas sensor element as defined in claim 1 wherein said current density is in the range of 20-150 milliamperes per square centimeter of the planar surface of said outer conductive catalyst electrode.

Claim 8

The process for pretreating a solid electrolyte oxygen gas sensor element as defined in claim 1 wherein, following the application of the direct current, the sensor element is maintained at said elevated temperature for a period of time after cessation of said current.

Claim 9

The process for pretreating a solid electrolyte oxygen gas sensor element as defined in claim 1 wherein said solid electrolyte body comprises zirconium dioxide.

Claim 10

The process for pretreating a solid electrolyte oxygen gas sensor element as defined in claim 8 wherein said inner and outer conductive catalyst electrodes are comprised of platinum.

Claim 11

The solid electrolyte oxygen gas sensor element pretreated according to the process of claim 1.

Claim 12

A process for pretreating a solid electrolyte oxygen gas sensor element so as to improve the operational properties thereof by increasing the voltage output under rich gas conditions, shortening the switching response time, and reducing the internal resistance thereof, wherein the sensor element comprises a zirconium dioxide solid electrolyte body having an inner conductive platinum electrode, that is to be in contact with a reference gas during operation of the sensor and an outer conductive platinum coating as an electrode over at least a portion of the outer surface thereof, that is to be in contact with a gas, the oxygen content of which is to be measured during operation of the sensor, and a porous protective coating over at least a portion of said outer electrode, comprising: (a) heating the sensor element to an elevated temperature in the range of 600°-900° C. and subjecting the outer surface thereof, with the platinum coating thereon, to a nitrogen atmosphere; and (b) applying a direct current to the sensor element, with said outer platinum coating electrode as an anode, while said outer surface is at said elevated temperature and in said nitrogen atmosphere, the current density thereof being about 20-150 milliamperes per square centimeter of the planar surface of said outer platinum coating electrode.

Claim 13

A process for pretreating a solid electrolyte oxygen gas sensor element so as to improve the operational properties thereof by increasing the voltage output under rich gas conditions, shortening the switching response time, and reducing the internal resistance thereof, wherein the sensor element comprises a zirconium dioxide solid electrolyte body having an inner conductive platinum electrode, that is to be in contact with a reference gas during operation of the sensor and an outer conductive platinum coating as an electrode over at least a portion of the outer surface thereof, that is to be in contact with a gas, the oxygen content of which is to be measured during operation of the sensor, and a porous protective coating over at least a portion of said outer electrode, comprising: (a) heating the sensor element to an elevated temperature in the range of 600°-900° C. and subjecting the outer surface thereof, with the platinum coating thereon, to a nitrogen atmosphere; and (b) applying a direct current to the sensor element, with said outer platinum coating electrode as an anode, while said outer surface is at said elevated temperature and in said nitrogen atmosphere, the current density thereof being about 20-150 milliamperes per square centimeter of the planar surface of said outer platinum coating electrode.

Claim 14

The process for pretreating a solid electrolyte oxygen gas sensor element as defined in claim 11 wherein, following the application of the direct current, the sensor element is maintained at said elevated temperature and with said outer platinum electrode in a nitrogen atmosphere for a period of time after cessation of said current.