No abstract

According to [1, 2], alkaline-earth modified lanthanum chromite with n-type conductivity can be used to make resistance heater elements capable of operating in an oxidizing medium up to 1800-1850~In our work on the manufacture of heaters, we used fused material obtained by a procedure developed in the Lebedev Physical Institute, Academy of Sciences of the USSR [3, 4] and described in [5]. The mixture for synthesis of calcium oxide-modified lanthanum chromite contained lanthanum oxide of LaO-1 grade according to TU 48-4-184-72 (purity not less than 99.849 wt.%), calcium oxide of OKhM-1 grade according to GOST 2912-73 (Cr20 a content 98 wt.%), and CaCO 3 of analytical reagent grade according to GOST 4530-66.The fused block was subjected to x-ray phase, petrographic, quantitative x-ray spectral, and x-ray structural analysis. The diffraction patterns of specimens from different sectors of the block show considerable redistribution of the intensities of the principal reflections in comparison with the distribution in the standard (Fig. 1). This indicates the presence of microstresses in the lattice of the solid solution obtained, or of impurities in the material; this is improbable.Petrographic analysis revealed a certain nonuniformity of the solid solution, noted during dark-field analysis and indicating the nonequilibrial state of the material. This is apparently due to incomplete homogenizatton of the melt during fusion and subsequent crystaUization, and to quenching of high-temperature

No abstract

No abstract