Crystal Structures of Cubic and Trigonal Yttrium Hypocarbides; A Dimorphically Interphased Single-Crystal Study

Abstract

X-ray structure determinations on the cubic YCx (x ≈ 0.3 − 0.7, stable above about 900°C) and the trigonal Y2C (stable below 900°C) have been carried out using a quenched “single crystal” in which a transient state in the midst of the cubic-to-trigonal transition has been arrested. Our “single crystal” is composed of one cubic and four trigonal single crystals, the trigonal c axis being parallel to one of four cubic body-diagonal axes. The cubic structure is of NaCl type with random holes in the carbon-atom sites and with a = 5.115 ± (2) Å for YC0.44. The ordering of the carbon atoms creates the anti-CdCl2-type trigonal Y2C with the yttrium positional parameter z = 0.2585 ± (3) in the hexagonal-based unit cell, a = 3.617 ± (2) and c = 17.96 ± (1) Å, containing three Y2C formula units. Mo Kα x-ray was employed, and consequently the dispersion corrections on the atomic scattering factor of Y amount to 10%–20% of the nondispersion value and are considerably larger than the carbon-scattering factor. The structure analyses with and without the dispersion corrections demonstrate that even these unusually large corrections do not modulate the Y and C positional parameters significantly. The x-ray single-crystal results were further substantiated by the neutron-powder analysis. The present work confirmed unambiguously not only the reported x-ray powder results as well as the neutron-powder data of the isostructural Ho2C, but also yielded the structural parameters with a much higher accuracy, hence providing detailed insights into the chemical-bonding correlation in the order–disorder transition.

Layered electrides as fluoride intercalation anodes

“…Another electride isostructural to Ca2N, Y2C, 41 is also a promising candidate for FiB anodes. Y2C, as shown in Figure 1e, can be represented as Y2 3+ N 3-2ewith 2enominally residing at the octahedral sites.…”

New Ternary Compounds Sc3B0.75C3, Sc2B1.1C3.2, ScB15C1.60 and Subsolidus Phase Relations in the Sc–B–C System at 1700°C

“…Much attention was paid to the role of oxygen solubility in this substoichiometric compound isotypic with NaCl (34, 36}38). The occurrence of superstructure formation in a sample with ScC stoichiometry (annealed (13503C) could be contradictingly interpreted on the base of a cubic supercell with doubled lattice parameter (32) or a trigonal structural model similar to Y C (35,39). While Ref.…”

Semimetallic bands derived from interlayer electrons in the quasi-two-dimensional electride Y2C

“…As shown in Fig. 2(a), the low-energy electron diffraction (LEED) pattern exhibits a hexagonal arrangement of spots corresponding to the reciprocal lattice of the R3m space group [19,20], thus indicating the obtainment of a clean and well-ordered Y 2 C surface. For the present ARPES study, soft x rays (SX) with a large probing depth were used to probe the intrinsic electride states because the anionic electron layer is expected to lie buried below the top [Y 2 C] 2+ layer.…”