Gas sensing element incorporated in a gas sensor for an internal combustion engine

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, wherein

• a ceramic porous protective layer is provided on a surface of said measured gas sensing electrode,
• said protective layer comprises coarse particles and fine particles 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 have a specific surface equal to or larger than 50 m2/g, and the other one of said fine and coarse particles has a specific surface less than 50 m2/g.

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, wherein

• a ceramic porous protective layer is provided on a surface of said measured gas sensing electrode,
• said protective layer comprises first particles and second particles mixed with each other so as to be structurally arranged in such a manner that interparticle cavities formed between said first particles are filled with said second particles, and
• at least one of said first particles and said second particles contain at least one selected from the group consisting of γ-Al203, θ-Al2O3, δ-Al2O3 and solid solution having the same crystal structure as those of γ-Al203, θ-Al203, δ-Al203, and the other one of said first and second particles is α-Al203.

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, wherein

• a ceramic porous protective layer is provided on a surface of said measured gas sensing electrode,
• said protective layer comprises first particles and second particles mixed with each other so as to be arranged in such a manner that interparticle cavities formed between said coarse particles are filled with said second particles, and
• at least one of said coarse particles and said fine particles have a specific surface equal to or larger than 50 m2/g, and the other one of said fine and coarse oarticles has a specific surface less than 50 m2/g.