Abstract: A highly corrosion resistant .alpha.-sialon-like sintered body consisting essentially of an .alpha.-sialon composition represented by the composition formulaMx(Si,Al).sub.12 (O,N).sub.16wherein M is at least one .alpha.-sialon-soluble element selected from the group consisting of Yb, Er and Dy, and 0<.times..ltoreq.0.8,and Sc.sub.2 O.sub.3 insoluble in the .alpha.-sialon composition and being in an amount of 0.01 to 15 wt % based on the weight of the sintered body, and containing as an intergranular phase a Sc.sub.2 O.sub.3 --SiO.sub.2 complex wherein the mole ratio of Sc.sub.2 O.sub.3 to SiO.sub.2 is within the range of 1:0.1 to 1:50. This sintered body has not only mechanical characteristics such as strength and toughness, but high corrosion resistance such that it can withstand use under an environment where corrosion resistance such as oxidation resistance or chemical resistance is required.

Abstract: A sensor comprising a solid electrolytic having oxygen ion conductivity to measure the amount of oxygen in molten metal by forming an oxygen concentration cell in which the solid electrolytic element is coated on the surface thereof with mixture which is composed of Al.sub.2 O.sub.3 powders and metallic fluoride powders such as MgF.sub.2 or CaF.sub.2.The present coating does not exfoliate at immersing the sensor into the molten metal and fully maintains wettability of the solid electrolytic element 1 and the molten metal, and since it does not hinder oxygen ion conductivity of the solid electrolytic element 1, the sensor rapidly reaches up to the thermal and electrical equilibrium state, thereby to obtain satisfactory emf wave.

Abstract: A composite sinter of silicon nitride/boron nitride, which consists essentially of, in weight percentage, silicon nitride within the range of from 60 to 97% and boron nitride within the range of from 3 to 40%, and wherein said boron nitride is present as a dispersed phase in the network of said silicon nitride; said composite sinter of silicon nitride/boron nitride being manufactured by the steps of: kneading a silicon powder within the range of from 47.3 to 95.1 wt.% and a boron nitride powder within the range of from 4.9 to 52.7 wt. %, as raw materials, with the use of an organic solvent solution containing a dispersant and a binder; press-forming the resultant kneaded mixture to prepare a green compact; sintering said green compact in a non-oxidizing atmosphere at a temperature within the range of from 1,100.degree. to 1,300.degree. C.