Crystal chemistry and magnetism of ternary actinoid boron carbides UB[sub 1[minus]x]C[sub 1+x] and U[sub 1[minus]x]M[sub x]B[sub 2]C with M = Sc, Lu, and Th

Journal Article · Tue Jun 01 04:00:00 EDT 1993 · Journal of Solid State Chemistry; (United States)

DOI:https://doi.org/10.1006/jssc.1993.1173· OSTI ID:5856220

Rogl, P ^[1]; Rupp, B ^[2]; Felner, I ^[3]; Fischer, P ^[4]

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1. Universitaet Wien, Vienna (Austria)
2. Universitaet Wien, Vienna (Austria) Lawrence Livermore National Lab., CA (United States)
3. Hebrew Univ., Jerusalem (Israel)
4. Eidgenoessische Technische Hochschule, Zuerich (Switzerland) Paul Scherrer Institut, Villigen (Switzerland)

Within the homogeneous range of uranium monocarbide UB[sub 1[minus]x]C[sub 1+x], the crystal structures of stoichiometric UBC and of the carbon-rich solid solution UB[sub 0.78]C[sub 1.22] have been refined from single-crystal X-ray counter data. From X-ray analysis crystal symmetry in both cases is consistent with the centrosymmetric space group Cmcm and there are no indications of superstructure formation. In contrast to the fully ordered atom arrangement revealed for stoichiometric UBC, random occupation by boron and carbon atoms is observed for the boron site in UB[sub 0.78]C[sub 1.22]. Neutron powder diffraction experiments at 9 and 295 K unambiguously revealed full occupancy by the nonmetal atoms in UB[sub 0.78]C[sub 1.22] and prove the statistical occupation of B and C atoms in the B-sites. The boron-boron chain in Cmcm (B-B = 0.1874 nm) is dissolved into boron pairs (B-B = 0.1706 nm). The formation of C-B-B-C groups corresponds to the structure types of ThBC and Th[sub 3]B[sub 2]C[sub 3]. The magnetic behavior has been investigated in the temperature range from 4.2 K to 1000 K for UB[sub 1[minus]x]C[sub 1+x] (UBC-type) and U[sub 1[minus]x]M[sub x]B[sub 2]C (ThB[sub 2]C-type for the high temperature modification and 1-UB[sub 2]C-type for the low temperature modification) with U partially substituted by Th or Sc, Lu. From magnetic susceptibilities, the alloys UB[sub 1[minus]x]C[sub 1+x] reveal temperature independent paramagnetism with typical intermediate valence fluctuation behavior (T[sub SF] [approximately] 350 K). ThB[sub 2]C and 1-UB[sub 2]C both are temperature independent paramagnets, whereas h-UB[sub 2]C is a ferromagnet with the rather high Curie temperature T[sub M] = 80(2) K. T[sub M] and the saturation magnetization per U atom both successively decrease on substitution of U by Th, Sc, or Lu in UB[sub 2]C, whereas the U-moments remain practically unchanged at [mu][sub eff](U) [approximately] 1.9 [mu][sub B]. 20 refs., 8 figs., 5 tabs.

• DOE Contract Number: W-7405-ENG-48
• OSTI ID: 5856220
• Journal Information: Journal of Solid State Chemistry; (United States), Journal Name: Journal of Solid State Chemistry; (United States) Vol. 104:2; ISSN 0022-4596; ISSN JSSCBI
• Country of Publication: United States
• Language: English

Related Subjects

36 MATERIALS SCIENCE
360202* -- Ceramics
Cermets
& Refractories-- Structure & Phase Studies
360204 -- Ceramics
Cermets
& Refractories-- Physical Properties
ACTINIDE COMPOUNDS
BORIDES
BORON COMPOUNDS
CARBIDES
CARBON COMPOUNDS
COHERENT SCATTERING
CRYSTAL LATTICES
CRYSTAL STRUCTURE
DIFFRACTION
FERROMAGNETIC MATERIALS
LUTETIUM BORIDES
LUTETIUM CARBIDES
LUTETIUM COMPOUNDS
MAGNETIC MATERIALS
MAGNETIC PROPERTIES
MAGNETISM
MATERIALS
MONOCLINIC LATTICES
NEUTRON DIFFRACTION
ORTHORHOMBIC LATTICES
PARAMAGNETISM
PHYSICAL PROPERTIES
RARE EARTH COMPOUNDS
SCANDIUM BORIDES
SCANDIUM CARBIDES
SCANDIUM COMPOUNDS
SCATTERING
TEMPERATURE DEPENDENCE
TEMPERATURE RANGE
TEMPERATURE RANGE 0000-0013 K
TEMPERATURE RANGE 0065-0273 K
TEMPERATURE RANGE 0273-0400 K
TEMPERATURE RANGE 0400-1000 K
THORIUM BORIDES
THORIUM CARBIDES
THORIUM COMPOUNDS
TRANSITION ELEMENT COMPOUNDS
URANIUM BORIDES
URANIUM CARBIDES
URANIUM COMPOUNDS