L 79 Lipatnikov, V. N. Atomic–Vacancy Ordering in the arbide Phase zeta--Ta4C3 –x [Text] / V. N. Lipatnikov, A. I. Gusev // Physics of the Solid State. - 2006. - Vol. 48, № 9. - P1634-1645. - Bibliogr. : p. 1645 (30 ref.) Рубрики: ХИМИЧЕСКИЕ НАУКИ Кл.слова (ненормированные): КАРБИД ТАНТАЛА -- НЕСТЕХИОМЕТРИЯ -- АТОМНО-ВАКАНСИОННОЕ УПОРЯДОЧЕНИЕ Аннотация: The structure of the nonstoichiometric trigonal (rhombohedral) carbide zeta--Ta4C3 –x forming in the tantalum–carbon system is studied by neutron diffraction, x-ray diffraction, and metallography. The unit cell parameters of the trigonal (space group ) carbide zeta-Ta4C3 –x(TaC0.67) are found to be ah= 0.3123 nm and ch= 3.0053 nm. It is shown that the metallic close-packed sublattice of the zeta-Ta4C3 –x phase consists of alternating blocks in which the metallic atoms are arranged in the same manner as on the fcc sublattice of the cubic carbide TaCy and the hcp sublattice of the hexagonal carbide Ta2C, respectively, and that the former sublattice is intermediate between the latter two sublattices. We are the first to establish experimentally that the distribution of carbon atoms and structural vacancies in the zeta-Ta4C3 – x carbide is ordered and to calculate the istribution function of carbon atoms over the nonmetallic-sublattice sites involved in the ordering. The results obtained for the zeta-Ta4C3 – x phase are used to refine the phase diagram of the Ta–C system Полный текст |