Crystal structure and electronic properties of the new compounds, U6Fe16Si7 and its interstitial carbide U6Fe16Si7C

Phase relations and stabilities at 900°C in the U–Fe–Si ternary system

“…No evidence for any deviation from stoichiometry could be detected from microprobe analyses and X-ray powder experiments [7]. U 6 Fe 16 Si 7 crystallizes in the cubic Mg 6 Cu 16 Si 7 -type with lattice parameter refined from powder data, a ¼ 11.7217(5) Å , which compares well with the value obtained from single crystal refinement [8]. Its crystal structure defines octahedral voids composed of six uranium atoms, which can easily accommodate interstitial elements such as O or C. On the opposite, insertion of Si or Fe at this position was found not pertinent by EDS and structural analyses.…”

“…The temperature dependences of the electrical resistivity and thermopower of U 3 Fe 2 Si 7 , U 2 FeSi 3 , U 1.2 Fe 4 Si 9.7 , U 2 Fe 3 Si 5 and UFe 2 Si 2 ternary phases have been recently presented [6]. The novel intermediate phases UFe 5 Si 3 [7] and U 6 Fe 16 Si 7 [8] have been structurally characterized, and their magnetic and transport properties measured. As a final step on the crystal-chemistry investigation of the intermediate phases of the UeFeeSi ternary system, we present here the assessment in an extended concentration range of the isothermal section of this phase diagram at 900 C as well as information about the phase formation.…”

Crystal structure and electronic properties of the new compounds U3Co12−xX4 with X=Si, Ge

“…1b). The maximum residual electron density, located near the Co2 site, reached a low value of 3.27 electrons perÅ 3 , which is usually observed for U-based compounds with unit-cell volume similar to that of U 3 Co 12 À x Ge 4 [20,21]. The chemical formula deduced from the crystallographic analysis is U 3 Co 11.66 Ge 4 which perfectly matches the result of our methodical microprobe experiments that reveal a small deficit on the cobalt sublattice, indicating that U 3 Co 12 À x Ge 4 has a homogeneity domain 0.0(2) oxo1.0(2 reductions, of few hundredths of Angström, of the unit-cell parameters a and c are observed for U 3 Co 11 Ge 4 compared to U 3 Co 12 Ge 4 .…”

Isothermal section of the ternary phase diagram U–Fe–Ge at 900 °C and its new intermetallic phases

“…Nevertheless, the lattice constant was successfully obtained as a = 11.923(6) Å by analogy with the structural archetype Mg 6 Cu 16 Si 7 (space group Fm m). This crystal structure is a ternary ordered variant of the Th 6 Mn 23 -type structure, which can accommodate interstitial elements in octahedral cages formed by uranium atoms, as it was demonstrated for C insertion in the lattice of the silicon analogue compound, U 6 Fe 16 Si 7 [38].…”