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Im System Al2O3‐Cr,O3‐P2O5 werden röntgenographisch die binären Phasen (I)‐(III) nachgewiesen und das Zustandsdiagramm konstruiert.

Solid electrolytes of zirconium dioxide completely or partly stabilized with yttrium oxide (ChSTs) are finding increasing use for making electrochemical sensors. We are aware [i] of a solid electrolyte made of ZrO 2 with molar parts of Y203 equal to 4%, working in oxygen sensors at temperatures of from 300 to 1700~A number of patents exist [2]* for compositions of solid electrolytes of the ChSTs type. Moreover, ceramics have been patented* for zirconia partly stabilized with Y203 (molar parts 0.5-5.0%) and/or other oxides (rare-earth elements, potassium, magnesium) consisting of 30-100% tetragonal modifications, and containing in the surface layer of the stabilizing oxide 1-20% more than in the average volume. The ceramic is coated with a layer of powder suspension with 12% Y203 and/or other stabilizing oxides, followed by sintering at 1000-1600 ~ as a result of which a surface layer is formed with the cubic modification, 0.1-200 ~m thick.The tetragonal monoclinic inversion of zirconia is used in order to increase the thermal-shock resistance and mechanical strength of the zirconia ceramics. To preserve the stability of the tetragonal phase at room temperatures, the grain size of the ceramic should be in the range 0.03-1.50 Dm. The presence in the ceramic of a second (cubic) phase limits the growth of the tetragonal grains [3].Oxygen conductivity of tetragonal ZrO 2 is noted in the same temperature and oxygenpressure region as in the cubic, but the electrical resistance of the tetragonal zirconia is 1.5-2.0 times greater than in the cubic. It is known [4] that high-temperature aging reduces the strength of ChSTs ceramics, but in ceramics stabilized with Y203 this reduction is slight and does not exceed 10%.We studied the possibility of obtaining ceramics from ChSTs for solid electrolytes with the simultaneous application of an electrode layer, which enables us to form a cubic structure in it, preventing the spreading of a monoclinic phase deep down, and which will increase the density and reduce the electric resistance of the solid electrolyte. The electrode layer was applied by using additions of materials with an electron conductivity used in the compositions of current-conducting materials for electric heaters [5,6]. The task was complicated by the fact that the penetration of the stabilizing additives (rareearth oxides and materials with electron conductivity) in the base material should be minimal, so as not to create a support layer (with a high electrical resistance) on the surface of the solid electrolyte.The investigations were done on specimens prepared from ZrO 2 partly stabilized with Y203 (mass 6.2%). Specimen tablets of diameter and height i0 nun and rods measuring 5 • 5 x 55 mm were extruded or cast under pressure using thermoplasticized bodies; firing was done in a tempering cycle and subsequent annealing in air.The coating was applied by using a slip containing both a solution of polyvinyl alcohol and powdered zirconia with additions (see Table i , 18), and also a mixture of a solution of chlori...

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An investigation of the reaction of aqueous solutions of sodium metaphosphate with the refractomy oxides of magnesium and calcium and their mixtures over a wide temperature range is of considerable practical significance for an elucidation of the mechanism of the formation of magnesia concretes with sodium phosphate binders. The investigation was carried out by derivatographic, x-ray, and IR-spectroscopic methods.The starting components were an aqueous solution of sodium metaphosphate NaPO 3 produced by dissolving analytically pure monosodium phosphate in water, CaO produced by calcining CaCO 3 of extreme purity at 1200~ analytically pure reactive MgO, and the electrofusion products of the various grain-size fractions.Suspensions of Mg(OH)2, Ca(OH)2 and their mixtures [Mg(OH) 2 + Ca(OH)2 ] were added to the Nal~:~ solution. The suspensions were prepared by dissolving the calcium hydroxide and reactive magnesium oxide in water.The resulting liquors were dried at 120~ with constant stirring. The resulting powders were molded into tablets which were fired at various temperatures. The composition of the investigated mixes is given in Table 1.