Collect. Czech. Chem. Commun. 1984, 49, 944-953

Investigation of the products of reaction of (Sc, Y)2O3 and (Sc, Dy)2O3 mixed crystals with carbon in proportions corresponding to the formation of M15C19 phase

Bohumil Hájek, Pavel Karen and Vlastimil Brožek

Department of Inorganic Chemistry, Prague Institute of Chemical Technology, 166 28 Prague 6


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 (Sc0,94Dy0,06)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.