Collection of Czechoslovak Chemical Communications - digital archive 

Abstract

Scandium, yttrium, and dysprosium formates were subjected to reaction with carbon in a stoichiometric ratio of M₂O₃ : C = 1 : (83/15) at 1 650 °C and 1 Pa for 40 h to give products containing typical phases of Sc₂OC and Sc₁₅C₁₉, Y₂OC and YC₂, and Dy₂OC and DyC₂, respectively (Y₂OC and Dy₂OC Fm3m, a = 494.7 ± 0.2 and 495.0 ± 0.2 pm, respectively). The mixed scandium-yttrium or scandium-dysprosium carbides prepared under the same conditions did not exhibit diffraction patterns of the M₁₅C₁₉ carbides, and were constituted by mixed dicarbide and mixed oxide-carbide crystals. Yttrium and, to a greater extent, dysprosium are preferentially located in the dicarbide structure, whereas scandium occupies more the oxide-carbide structure. The mixed scandium-dysprosium carbide (Sc_0,94Dy_0,06)₁₅C₁₉ (P42₁c, a = 753 ± 1 pm, c = 1 506 ± 3 pm) starts to form at temperatures above the melting temperature of the mixture (1750-1800 °C). The composition of the gaseous products of hydrolysis is consistent with the phase composition of the samples. The method of quantitative phase analysis based on the GLC analysis of the gases evolved on the hydrolysis is employed for the analysis of complex phase systems. In addition to chemical and X-ray diffraction analysis, the hydrolysis method is also applied to the determination of additional products.