Gas sensors and the manufacturing method thereof

Abstract

A gas sensor characterized in that the gas sensor has at least: an insulating substrate; a pair of thin film electrodes which are spaced apart at a given interval and provided on the insulating substrate; a thin film gas sensitive layer which is provided on both the substrate and the thin film electrodes, the gas sensitive layer containing a given material as main ingredient; and a pair of thick film electrodes which is correspondingly positioned over the pair of thin film electrodes and provided on the thin film gas sensitive layer, wherein the thin film electrodes and the thick film electrodes are formed so as to sandwich portions of the thin film gas sensitive layer between the two types of electrodes.

What is claimed is:  
     
         1 . A gas sensor characterized in that said gas sensor comprises at least: 
 an insulating substrate;    a pair of thin film electrodes which are spaced apart at a given interval and provided on said insulating substrate;    a thin film gas sensitive layer which is provided on both said substrate and said thin film electrodes, said gas sensitive layer containing a given material as main ingredient; and    a pair of thick film electrodes which is correspondingly positioned over said pair of thin film electrodes and provided on said thin film gas sensitive layer,    wherein said thin film electrodes and said thick film electrodes are formed so as to sandwich portions of said thin film gas sensitive layer between said two types of electrodes.    
     
     
         2 . A gas sensor characterized in that said gas sensor comprises at least: 
 an insulating substrate;    a pair of thin film electrodes which are spaced apart at a given interval and provided on said insulating substrate;    a thin film gas sensitive layer which is provided on both on said substrate and said thin film electrodes, said sensitive layer containing a given material as main ingredient; and    a pair of thick film electrodes which is correspondingly positioned over said pair of thin film electrodes and provided in contact with said thin film electrodes.    
     
     
         3 . The gas sensor according to  claim 1  or  2  characterized in that the interval between said pair of thick film electrodes is longer than the interval between said pair of thin film electrodes.  
     
     
         4 . The gas sensor according to  claim 3  characterized in that said given material comprises tin oxide as main ingredient and at least one additional element selected from the group consisting of palladium, iron, nickel, manganese, cobalt and zinc.  
     
     
         5 . A method of manufacturing a gas sensor characterized in that a process is provided wherein a thin film gas sensitive layer is formed by coating an organic solution containing a metal tin salt, an organic compound capable of coordinating to at least a tin and an activator, and then by firing said solution.  
     
     
         6 . The method of manufacturing a gas sensor according to  claim 5  characterized in that said metal tin salt is at least one compound selected from the group consisting of stannous chloride, tin acetylacetonate complex and tin 2-ethylhexanoate.  
     
     
         7 . The method of manufacturing a gas sensor according to  claim 5  or  6  characterized in that said organic compound capable of coordinating to a tin is at least one compound selected from the group consisting of β-diketones, etheralcohols, polyhydric alcohols, and condensation products of the polyhydric alcohols.  
     
     
         8 . A method of manufacturing a gas sensor characterized in that a process is provided wherein a thin film gas sensitive layer is formed by coating a paste comprising an organic solution containing at least a metal tin soap, an activator and a viscosity controller, and then by firing said paste.  
     
     
         9 . The method of manufacturing a gas sensor according to  claim 8  characterized in that said metal tin soap is tin 2-ethylhexanoate and/or tin naphthenate.  
     
     
         10 . The method of manufacturing a gas sensor according to  claim 8  or  9  characterized in that said viscosity controller is polyvinyl pyrrolidinone and/or ethyl cellulose.  
     
     
         11 . The method of manufacturing a gas sensor according to  claims 5  to  10  characterized in that said activator has at least one element selected from the group consisting of palladium, iron, nickel, manganese, cobalt and zinc, said activator being at least one compound selected from the group consisting of metal chlorides, metal acetylacetonate complexes and metal soaps.