FORNASINI , Maria Luisa

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Segments of the basic structures BaAl4, AlB2, W, Po, Cu3Au, CaF2 or hybrids obtained combining two segments of these types are used with the mechanism of intergrowth to describe nine linear structures of binary and ternary intermetallic compounds formed by rare earth or alkaline earth metals. Such a representation allows to display relationship...

The crystal structure of Ba5Ga6 was determined by single-crystal diffractometry. It is hexagonal, hP22, space group P6c2 (n. 188), a = 7.771(2) A ̊, c = 14.376(4) A ̊, Z = 2, refined with anisotropic displacement factors, R = 0.076 with 358 reflections, and contains a disordered Ba position with partial occupation. The structure is...

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The crystal structures of two phases in the neodymium-gold system were determined by single crystal X-ray diffractometer methods, '/.(MoKx = 0.7107 A. Nd3Au4(hR42) is trigonal, R3 (n. 148), a = 13.739(3) A, c = 6.088(2) A, Z = 6, R = 0.083 with 405 reflections, isotypic with Pu3,Pd4. Nd,7Au36(tP 106) is tetragonal, P4/nmm (n. 129), a =...

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The Ca–Zn–Al system has been investigated in the region from 8 to 33 at% Ca. The results show that the following phases are solid solutions based on the corresponding known binary compounds: Ca(Zn1–xAlx)3 (x = 0 – 0.23, CaZn3 type), Ca(Zn1–xAlx)4 (x = 0.47 – 1.00, BaAl4 type), Ca1–y(Zn1–xAlx)5+2y (x = 0 – 0.12 and y = 0 – 0.12, CaCu5-derived...

The structures of ScAuSi, YAuSi and LuAuSi were determined by single-crystal diffractometry. ScAuSi, hP6, hexagonal P6m2 (no. 187), a=4.212(1) A ̊, c=7.546(3) A ̊, Z=2, R=0.039 using 66 reflections, represents a new ternary ordered type. YAuSi, hP6, hexagonal P63mc (no. 186),a=4.288(2) A ̊, c=7.546(3) A ̊, Z=2, R=0.039 using 66 reflections, is...

The ternary intermetallic compounds R3NiSi3 (R = La, Ce, Pr, Nd, Sm, Gd, Tb, Dy, Er, Tm), R3FeSi3 (R = Er, Tm) and R3CoSi3 (R = Er) have been synthesized and structurally characterized by X-ray diffraction on powders and single crystals. In particular, within the nickel series, the lighter rare earths (from La to Dy) adopt the orthorhombic...

The synthesis and structural characterization of phases in the R–Li–Ge (R = rare earth) systems are reported. The R4LiGe4 compounds with R = La–Nd, Sm complete the series, where the analogues with R = Gd–Tm, Lu were confirmed, all crystallizing with the Tm4LiGe4 type. Nd4LiGe4 and Ho4LiGe4 were structurally studied by single crystal X-ray...

Seventeen new RMX phases were synthesized in the systems with R Ca, Sr, Ba, Eu, Yb, M Mg, Hg and X Si, Ge, Sn, Pb. X-Ray analysis on powders and single crystals assigned the phases to five structure types: ZrBeSi, LiGaGe, TiNiSi, CeCu2 and ZrNiAl. The distribution of 180 possible RMX compounds among eight structural types is discussed in a...

25 new RMX phases (R ≡ Ca, Sr, Ba, Eu, Yb; M ≡ Zn, Cd; X ≡ Si, Ge, Sn, Pb) were found to crystallize in the structure types ZrBeSi, LiGaGe, TiNiSi, ZrNiAl and CeCu2. Single-crystal refinements were made for YbZnSn (LiGaGe type) with complete atomic ordering, and for SrCdSn, BaCdSn and BaCdPb with disordered CeCu2 structure. A two-dimensional...

19 intermetallic compounds with the general formula RMX (R ≡ Ca, Sr, Ba, Eu, Yb; M ≡ Cu, Ag, Au; X ≡ Sb, Bi) were synthesized and structurally studied by X-ray methods on powders and single crystals. The ternary phases crystallize in four ordered structural types: ZrBeSi, LiGaGe, TiNiSi and MgAgAs. Some comments are given on the parameters...

The ternary RAgX phases, with R = Ca, Sr, Ba, Eu, Yb and X = Si, Ge, Sn, Pb, were structurally studied by means of X-ray diffraction on powders and single crystals. The tin and lead compounds exist on the equiatomic composition and crystallize in the CeCu2, CaLiSn and YbAgPb types. The silicon and germanium compounds are in most cases...

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Au2Ca2Pb, tetragonal, P4/mbm (No. 127), a = 8.038(1) Å, c = 3.8254(4) Å, V = 247.2 Å3, Z = 2, Rgt(F) = 0.025, wRobs(F2) = 0.054, T=293 K.

The electrical resistivity of the phases CaAgBi, CaAuBi, YbAgBi in the range 10-300 K and CaCuBi, YbCuBi, YbAuBi in the range 10-600 K was measured. All compounds show metallic behaviour. The phonon contribution with an additional cubic term are used to represent the temperature dependence of the resistivity for the gold and silver phases....

The YbAu2-xSix and CaAu2-xSix systems were studied by X-ray techniques in the range 0.7 ≤ x ≤ 1.3. The YbAuSi compound forms peritectically at 1478 K and is stable till 1168 K in its high-temperature form (EuAuGe type); below 1168 K the SrAgGe type occurs. No equiatomic compound exists in the Ca-Au-Si system. In the gold- and silicon-rich...

Au2PbYb2, tetragonal, P42/mnm (No. 136), a = 8.037(2) Å, c = 7.465(2) Å, V = 482.2 Å3, Z = 4, Rgt(F) = 0.036, wRobs(F2) = 0.069, T=293 K.

The R2FeSi2 compounds with R=Gd, Tb, Dy, Ho, Er, Tm, Y, and R2CoSi2 with R=Ho, Er, Tm, were synthesized and studied by X-ray powder diffraction. All phases crystallize in the Sc2CoSi2 monoclinic structure type, and the atomic positional and thermal parameters were refined by single crystal data for Tb2FeSi2, Er2FeSi2 and Er2CoSi2. The...

CaLiPb, hexagonal, P6̄m2 (No. 187), a = 4.933(1) Å, c = 10.990(1) Å, V = 231.6 Å3, Z = 3, Rgt(F) = 0.048, wRall(F2) = 0.124, T = 293 K. LiPbYb, hexagonal, P6̄m2 (No. 187), a = 4.918(1) Å, c = 10.921 (3) Å, V = 228.8 Å3, Z = 3, Rgt(F) = 0.054, wRall(F2) = 0.109, T = 293 K.

Twelve ternary alloys in the Ca-Cu-Sn system were synthesized as a test on the existing phases. They were prepared from the elements sealed under argon in Ta crucibles, melted in an induction furnace and annealed at 700 °C or 600 °C. Four ordered compounds were found: CaCuSn (YbAuSn type), Imm2, a = 4.597(1)A ° , b = 22.027(2)A ° , c =...

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