Patent ID: 6632338
Filing Date: 2003-10-14
Classification: G01N

Abstract:
A gas sensing element comprising a solid electrolytic body, a reference gas sensing electrode provided on a surface of said solid electrolytic body so as to be exposed to a reference gas, a measured gas sensing electrode provided on another surface of said solid electrolytic body so as to be exposed to a measured gas, whereina ceramic porous protective layer is provided on a surface of said measured gas sensing electrode, said protective layer comprises coarse particles and fine particles structurally arranged in such a manner that interparticle cavities formed between said coarse particles are filled with said fine particles wherein said protective layer satisfies a relationship that a ratio RB/RA is equal to or larger than 3, where RA represents an average particle diameter of said fine particles while RB represents an average particle diameter of said coarse particles, and at least one of said coarse particles and said fine particles contain at least one selected from the group consisting of &ggr;-Al203, &thgr;-Al2O3, &dgr;-Al2O3 and solid solution having the same crystal structure as those of &ggr;-Al203, &thgr;-Al203, &dgr;-Al203, and the other one of said fine and coarse particles is &agr;-Al203.