Contamination-Resistant Gas Sensor Element

Abstract

A contamination-resistant sensor element and methods for making the same are provided. A sensor element may include a contamination-resistant coating on at least a portion thereof. The coating may comprise gamma-delta alumina and lithium oxide and may have a thickness of about 100 to about 600 microns and a porosity of about 20 to about 70 percent. The method may include using gamma-delta alumina and lithium oxide to form a mixture, applying the mixture to at least a portion of a sensor element, and temperature treated the mixture to form a contamination-resistant coating on the surface of the measuring cell.

1 . A sensor element comprising a contamination-resistant coating on at least a portion thereof, the coating comprising gamma-delta alumina and lithium oxide and having a thickness of about 50 to about 900 microns and a porosity of about 20 to about 70 percent.  
   
   
       2 . The element of  claim 1 , wherein the coating has a thickness of about 50 to about 300 microns.  
   
   
       3 . The element of  claim 1 , wherein the coating has a thickness of about 300 to about 900 microns.  
   
   
       4 . The element of  claim 1 , wherein the coating has a porosity of about 20 to about 45 percent.  
   
   
       5 . The element of  claim 1 , wherein the coating has a porosity of about 45 to about 70 percent.  
   
   
       6 . The element of  claim 1 , wherein the coating comprises about 40 to about 80 percent gamma-delta alumina by weight and about 1 to about 10 percent lithium oxide by weight.  
   
   
       7 . The element of  claim 1 , wherein the coating further comprises about 1 to about 10 percent lithium oxide by weight.  
   
   
       8 . The element of  claim 1 , wherein the portion of the element is a substrate having a plurality of edges, and wherein the coating does not touch or cover at least one of the edges.  
   
   
       9 . The element of  claim 8 , wherein the substrate is a surface of an electrolyte foil, and the surface has an exposed portion that is not covered by the coating.  
   
   
       10 . The element of  claim 9 , wherein the coating at least partially covers an electrode.  
   
   
       11 . The element of  claim 9 , wherein an adhesive is used to secure the coating to the substrate, and the adhesive adheres to at least a portion of the exposed portion and at least a portion of the coating.  
   
   
       12 . The element of  claim 11 , wherein the electrolyte foil has a side running perpendicular to the surface, and the adhesive adheres to at least a portion of the side.  
   
   
       13 . The element of  claim 11 , further comprising a protective layer comprising at least one of zirconium oxide, aluminum oxide, titanium oxide, magnesium oxide, and a combination thereof positioned between the coating and the foil.  
   
   
       14 . The element of  claim 1 , wherein the portion of the sensor element is a protective layer comprising at least one of zirconium oxide, aluminum oxide, titanium oxide, magnesium oxide, and a combination thereof.  
   
   
       15 . The element of  claim 1 , wherein the sensor element is a part of a stoichiometric or wide band automotive exhaust gas sensor.  
   
   
       16 . The element of  claim 1 , wherein the coating further comprises at least one of titanium oxide, lanthanum oxide, and a combination thereof.  
   
   
       17 . A sensor element comprising: 
 a substrate having a plurality of edges;    a contamination-resistant coating comprising gamma-delta alumina and lithium oxide applied to at least a portion of the substrate such that the coating does not touch or cover at least one of the edges, thereby leaving an exposed part of the substrate not covered by the coating; and    an adhesive adhering to at least a portion of the exposed part and at least a portion of the coating to secure the coating to the substrate.    
   
   
       18 . The element of claim  44 , wherein the coating further comprises at least one of a titanium oxide, lanthanum oxide, and a combination thereof.