The Mo2FeB2- and Mn2AlB2-Type Modifications of RE2Ni2Cd (Re = La, Pr, Nd, Sm, Tb, Dy)

2005 ◽  
Vol 60 (3) ◽  
pp. 271-276 ◽  
Author(s):  
Thomas Fickenscher ◽  
Ute C. Rodewald ◽  
Dirk Niepmann ◽  
Ratikanta Mishra ◽  
Marcus Eschen ◽  
...  
Keyword(s):  
Rare Earth ◽  
High Temperature ◽  
Low Temperature ◽  
Rare Earth Metal ◽  
High Frequency ◽  
Earth Metal ◽  
Two Dimensional ◽  
Space Group ◽  
X Ray ◽  
Sample Chamber

The rare earth metal (RE)-nickel-cadmium intermetallics RE2Ni2Cd (RE = La, Pr, Nd, Sm, Tb, Dy) were prepared from the elements in sealed niobium or tantalum tubes in a water-cooled sample chamber of a high-frequency furnace. They crystallize with a tetragonal Mo2FeB2 type low-temperature modification, space group P4/mbm, and an orthorhombic Mn2AlB2 type hightemperature modification, space group Cmmm. The cadmium compounds were characterized through their X-ray powder patterns. Five structures of the low-temperature modifications were refined from X-ray single crystal diffractometer data: α = 763.76(9), c = 387.26(8) pm, wR2 = 0.046, 205 F2 for La2Ni1.67(1)Cd; α = 752.93(7), c = 380.95(6) pm, wR2 = 0.061, 260 F2 for Pr2Ni2Cd; α = 750.88(9), c = 378.33(7) pm, wR2 = 0.051, 195 F2 for Nd2Ni2Cd; α = 743.6(1), c = 374.0(1) pm, wR2 = 0.036, 386 F2 for Sm2Ni1.93(1)Cd; α = 734.9(1), c = 366.1(2) pm, wR2 = 0.030, 252 F2 for Dy2Ni1.94(1)Cd, with 13(12) variables per refinement. The 4g nickel site is only fully occupied in the neodymium and the praseodymium compound. Both modifications can be considered as intergrowths of distorted AlB2 and CsCl related slabs. In both modification the nickel and cadmium atoms build up two-dimensional [Ni2Cd] networks. In the low-temperature modifications the nickel atoms form pairs, while nickel zig-zag chains occur in the high-temperature modifications. These nickel fragments are condensed via the cadmium atoms. The crystal chemistry and the chemical bonding in these intermetallics is discussed

Ternary Thallides REMgTl (Re = Y, La – Nd, Sm, Gd – Tm, Lu)

2005 ◽  
Vol 60 (3) ◽  
pp. 265-270 ◽  
Author(s):  
Rainer Kraft ◽  
Rainer Pöttgen
Keyword(s):  
Rare Earth ◽  
Single Crystal ◽  
Rare Earth Metal ◽  
High Frequency ◽  
Three Dimensional ◽  
Earth Metal ◽  
X Ray ◽  
Sample Chamber ◽  
Trigonal Prismatic Coordination ◽  
Trigonal Prismatic

The rare earth metal (RE)-magnesium-thallides REMgTl (RE = Y, La-Nd, Sm, Gd-Tm, Lu) were prepared from the elements in sealed tantalum tubes in a water-cooled sample chamber of a high-frequency furnace. The thallides were characterized through their X-ray powder patterns. They crystallize with the hexagonal ZrNiAl type structure, space group P62m, with three formula units per cell. Four structures were refined from X-ray single crystal diffractometer data: α = 750.5(1), c = 459.85(8) pm, wR2 = 0.0491, 364 F2 values, 14 variables for YMgTl; α = 781.3(1), c = 477.84(8) pm, wR2 = 0.0640, BASF = 0.09(2), 425 F2 values, 15 variables for LaMgTl; α = 774.1(1), c = 473.75(7) pm, wR2 = 0.0405, 295 F2 values, 14 variables for CeMgTl; a = 760.3(1), c = 465.93(8) pm, wR2 = 0.0262, 287 F2 values, 14 variables for SmMgTl. The PrMgTl, NdMgTl, GdMgTl, TbMgTl, and DyMgTl structures have been analyzed using the Rietveld technique. The REMgTl structures contain two cystallographically independent thallium sites, both with tri-capped trigonal prismatic coordination: Tl1Mg3RE6 and Tl2Mg6RE3. Together the magnesium and thallium atoms form three-dimensional [MgTl] networks with Mg-Mg distances of 327 and Mg-Tl distances in the range 299 - 303 pm (data for CeMgTl)

Synthesis and structure determination of Ce6Cd23Te: a new chalcogen-containing member of theRE6Cd23T family (REis a rare-earth metal and T is a late group 14, 15 and 16 element)

2017 ◽  
Vol 73 (2) ◽  
pp. 121-125 ◽  
Author(s):  
Griffen Desroches ◽  
Svilen Bobev
Keyword(s):  
Rare Earth ◽  
Single Crystal ◽  
Rare Earth Metal ◽  
Earth Metal ◽  
X Ray Diffraction ◽  
Space Group ◽  
X Ray ◽  
Valence Fluctuations ◽  
High Temperature Reaction ◽  
Pearson Symbol

The ternary phase hexacerium tricosacadmium telluride, Ce6Cd23Te, was synthesized by a high-temperature reaction of the elements in sealed Nb ampoules and was structurally characterized by powder and single-crystal X-ray diffraction. The structure, established from single-crystal X-ray diffraction methods, is isopointal with the Zr6Zn23Si structure type (Pearson symbolcF120, cubic space groupFm-3m), a filled version of the Th6Mn23structure with the same space group and Pearson symbolcF116. Though no Cd-containing rare-earth metal binaries are known to form with this structure, it appears that the addition of small amounts of ap-block element allows the formation of such interstitially stabilized ternary compounds. Temperature-dependent direct current (dc) magnetization measurements suggest local-moment magnetism arising from the Ce3+ground state, with possible valence fluctuations at low temperature, inferred from the deviations from the Curie–Weiss law.

Sc14Co3.10In2.59 – the representative of the Lu14Co3In3 type with the smallest rare earth element

2020 ◽  
Vol 75 (8) ◽  
pp. 799-803
Author(s):  
Nataliya L. Gulay ◽  
Yaroslav M. Kalychak ◽  
Rainer Pöttgen
Keyword(s):  
Rare Earth ◽  
Rare Earth Metal ◽  
High Frequency ◽  
Earth Element ◽  
Structure Refinement ◽  
Earth Metal ◽  
Direct Reaction ◽  
Slow Cooling ◽  
Rich Phase ◽  
X Ray

AbstractThe scandium-rich phase Sc14Co3.10In2.59 has been synthesized by a direct reaction of the elements in a sealed tantalum ampoule in a high-frequency furnace. Single crystals were obtained by slow cooling of the product. The Sc14Co3.10In2.59 structure was refined from single-crystal X-ray diffractometer data: Lu14Co3In3 type, P42/nmc, a = 889.13(13), c = 2138.7(4) pm, wR2 = 0.0483, 1636 F2 values, and 64 variables. Sc14Co3.10In2.59 completes the series of the rare earth metal-rich phases RE14Co3In3. The structure refinement revealed defects on the Co1 site (84.7(5)% occupancy on 8g) and a mixed occupancy of 59.1(7)% In1/40.9(7)% Co3 on the 4c site. The structure is built up by a dense condensation of Co@Sc6 trigonal prisms and In2@InSc11 and In1/Co2@Co2Sc10 icosahedra. An interpenetration of the In2@InSc11 icosahedra leads to dumb-bell formation with an In2–In2 distance of 289 pm. The Sc14Co3.10In2.59 structure is stabilized by substantial Sc–Sc bonding (316–360 pm Sc–Sc).

X-Ray Diffraction Study of Rare Earth Epitaxial Structures Grown by MBE onto (111) GaAs

1989 ◽  
Vol 151 ◽  
Author(s):  
W. R. Bennett ◽  
R. F. C. Farrow ◽  
S. S. P. Parkin ◽  
E. E. Marinero
Keyword(s):  
Rare Earth ◽  
Molecular Beam Epitaxy ◽  
Rare Earth Metal ◽  
Molecular Beam ◽  
Earth Metal ◽  
Magnetic Ordering ◽  
Metal Films ◽  
X Ray Diffraction ◽  
X Ray ◽  
Strain Components

ABSTRACTWe report on the new epitaxial system LaF3/Er/Dy/Er/LaF3/GaAs (111) grown by molecular beam epitaxy. X-ray diffraction studies have been used to determine the epitaxial relationships between the rare earths, the LaF3 and the substrate. Further studies of symmetric and asymmetric reflections yielded the in-plane and perpendicular strain components of the rare earth layers. Such systems may be used to probe the effects of magnetoelastic interactions and dimensionality on magnetic ordering in rare earth metal films and multilayers.

Structural chemistry of NaCoPO4

1996 ◽  
Vol 52 (3) ◽  
pp. 440-449 ◽  
Author(s):  
R. Hammond ◽  
J. Barbier
Keyword(s):  
High Temperature ◽  
Low Temperature ◽  
Large Family ◽  
X Ray Diffraction ◽  
Tetrahedral Framework ◽  
Space Group ◽  
X Ray ◽  
Cell Parameters ◽  
Tetrahedral Sites ◽  
Bond Valence Analysis

Sodium cobalt phosphate, NaCoPO4, occurs as two different polymorphs which transform reversibly at 998 K. The crystal structures of both polymorphs have been determined by single-crystal X-ray diffraction. The low-temperature form α-NaCoPO4 crystallizes in the space group Pnma with cell parameters: a = 8.871 (3), b = 6.780 (3), c = 5.023 (1) Å, and Z = 4 [wR(F 2) = 0.0653 for all 945 independent reflections]. The α-phase contains octahedrally coordinated Co and Na atoms and tetrahedrally coordinated P atoms, and is isostructural with maracite, NaMnPO4. The structure of high-temperature β-NaCoPO4 is hexagonal with space group P65 and cell parameters: a = 10.166 (1), c = 23.881 (5) Å, and Z = 24 [wR(F 2) = 0.0867 for 4343 unique reflections]. The β-phase belongs to the large family of stuffed tridymites, with the P and Co atoms occupying tetrahedral sites and the Na atoms located in the cavities of the tetrahedral framework. The long c axis corresponds to a 3 × superstructure of the basic tridymite framework (c ≃ 8 Å) and is caused by the displacement of the Na atoms, tetrahedral tilts and strong distortions of the CoO4 tetrahedra. A bond-valence analysis of these phases reveals that the polymorphism in NaCoPO4 is due in part to over-/underbonding of the Na atom in the low-/high-temperature structures, respectively.

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