Abstract: An alumina-based sintered material for ceramic heater having a resistance heater embedded in its ceramic material. With the total amount of Al.sub.2 O.sub.3, SiO.sub.2, MgO and CaO being 100 wt %, the sintered material contains 91 to 97 wt % of Al.sub.2 O.sub.3, 1 to 8 wt % of SiO.sub.2, 0.2 to 1.2 wt % of MgO and 0.2 to 1.2 wt % of CaO, the total amount of MgO and CaO being 0.4 to 1.8 wt %, whereas, for the total amount of Al.sub.2 O.sub.3, MgO and CaO of 100 wt %, 0.1 to 15 wt % of (a) at least one of rare earth elements and groups IVa excluding Ti, Va and VIa of the Periodic Table are contained in the sintered material. In place of (a), 0.2 wt % or less of other elements (Na, K, Fe, Ti etc.) may also be contained in an amount not more than 0.2 wt %, calculated in terms of oxides.

Abstract: A method for producing an oxygen detection element having uniform pores and an excellent durability against toxic matter contained in the measurement gas. The method includes a first step of applying a paste to be sintered to form a catalytic electrode layer onto at least a part of an oxygen-ion conductive solid-state electrolytic body, and sintering the paste to thereby form said catalytic electrode layer at a predetermined position on said surface of said solid-state electrolytic body after sintering, and a second step of forming an electrode protection layer for coating and protecting at least a part of the catalytic electrode layer either after or simultaneous with the first step. In a first embodiment, the paste contains mainly a noble metal powder acting as a catalyst and an organic metal compound, in a second embodiment mainly co-precipitated powder consisting of a noble metal and a metal hydroxide, and in a third embodiment mainly noble metal powder and a powder of a metal other than a noble metal.

Abstract: An oxygen sensor comprising a hollow cylindrical member closed at one end but open at the other to admit a reference gas. There is at least one radial through-hole in the hollow cylindrical member. An oxygen-ion conductive solid electrolyte later has at least one pair of electrodes on its opposite sides. The electrolyte layer is wrapped around the hollow cylindrical member with the electrode on its inner side facing the through hole. In other embodiments, an oxygen sensor is provided which is very insensitive to the direction of flow of the gas to be analyzed. The electrodes of the sensor are spaced at substantially equal intervals on the circumference of a cylindrical solid electrolyte layer in registry with through-holes formed in a hollow tubular member surrounded by the electrolyte layer. A heating unit may be formed on either the inner or outer surface of the solid electrolyte layer.