Abstract: A method of fabricating a sintered ceramic composite body having at last one hollow portion therein is disclosed. According to this method, at least one green ceramic body in the form of a sheet or plate and an adhesive sheet made of a ceramic powder and a binder resin are provided. The adhesive sheet is capable of adhering to the green ceramic body after drying and is shaped to provide a hollow portion in association with green ceramic body. The adhesion body and the green ceramic body are brought into intimate contact with each other so that a hollow portion is established therebetween. The resulting composite body is pressed and sintered to obtain a sintered ceramic composite body having the hollow portion therein. The binder preferably includes acrylic resin(s) and/or vinyl resin(s) having a molecular weight of 300,000 to 800,000 and a glass transition temperature of -30.degree. C. or below.

Abstract: An oxygen sensor has alumina porous layer on a surface of a solid electrolyte to cover electrodes and the alumina porous layer is simultaneously baked with the solid electrolyte. The alumina porous layer has baking contraction percentage which is the same range of the solid electrolyte. Alumina powder which is a starting material of the alumina porous layer includes 0.3 to 0.5 .mu.m of a 50% grain size, 0.4 to 1.1 .mu.m of a 70% grain size, and 0.8 to 4.0 .mu.m of a 90% grain size in a grain size distribution of weight integration frequency and further a specific surface area according to a BET method is approximately 8.5 to 11.0 m.sup.2 /g. It is preferable that the baking contraction percentages of the solid electrolyte and alumina porous layer are approximately 16 to 22%.