Abstract:
The structure of the ζ-Ta4C3−x nonstoichiometric trigonal (rhombohedral) carbide, which is formed in the tantalum-carbon system, has been analyzed by neutron diffraction, x-ray diffraction, and metallography. The ordered distributions of carbon atoms and structure vacancies have been experimentally determined and the distribution function of carbon atoms over the nonmetallic-sublattice sites, where ordering occurs, has been calculated. The parameters of the unit cell of the ζ-Ta4C3−x (TaC0.67) trigonal (space group R[`3] mR\overline 3 m ) carbide are found to be aH = 0.3123 nm and cH = 3.0053 nm. It has been shown that the metallic close packed sublattice of the ζ-Ta4C3−x carbide is formed by alternating blocks, where metal atoms are located both in the fcc and hcp sublattices of the TaCy cubic and Ta2C hexagonal carbides, respectively.
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