MERLO , Franco

The atomic volume of an AxByCz ternary intermetallic compound can be calculated starting from volumes of some proper AB, AC and BC binary phases. The three methods by Colinet, Muggianu and Kohler, originally used to estimate thermodynamic quantities, and a new method here proposed, were tested to derive volume data in eight systems containing...

The electrical resistivity of the intermetallic compounds LaAg, CeAg and YAg has been measured in the range 10-800 K. The data on YAg are described by the usual Block-Gruneisen formula, but both CeAg and LaAg show higher resistivity values and a different thermal dependence. These anomalies can be ascribed to valence instabilities of the two...

The intermetallic compounds Yb2Ge, Eu2Ge and Eu2Si were synthesized from the elements by HF melting in tantalum crucibles. The three phases crystallize in the PbCl2 structure type, as shown by Rietveld refinement of powder pattern intensity data. The structure of Yb2Ge was confirmed by a single crystal study.

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 new R2Co2Al compounds (R = Pr, Nd, Sm, Gd, Tb, Dy, Ho, Er, Tm, Y), studied by single crystal and powder X-ray diffraction, crystallize with the W2CoB2 structure type. Pr2Co2Al is dimorphic, showing also its own monoclinic structure (a = 9.595 Å, b = 5.602 Å, c = 7.753 Å, β = 103.89°), which is closely related to the W2CoB2 type. Both...

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...

No description

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 =...

X-Ray diffraction on powders and single crystals has been used to study some phases in the YbMnSi1-xGex system. YbMnGe is dimorphic: the high-temperature form, stable above 1423 K, crystallizes in the hexagonal ZrNiAl-type structure, while the low-temperature form, stable below 1073 K, is orthorhombic with TiNiSi-type. The structural transition...

Several samples were prepared in the title systems, starting from the elements sealed under argon in Ta crucibles, melting in an induction fornace and annealing at 823 K. Six ternary phases were found: EuCu2Sn 2, a = 11.100 (3), b = 4.307 (1), c = 4.824 (1) , β = 108.88 (1)°, and SrCu2Sn2, a = 11.197 (4), b = 4.322 (2), c = 4.859 (1) , β =...

The RCuZn, RAgZn and RAgAl intermetallic compounds (R = rare earth metals) were synthesized and structurally studied by powder and single crystal X-ray diffraction. Among the 28 examined phases, YbAgAl crystallizes in the MgZn2 structure type, while all the others belong to the CeCu2 type. The usual decrease of the cell parameters from...

The phases CaMgAg, YbMgAg, CaMgPd, and YbMgPd were synthesized by melting the constituent metals in sealed tantalum crucibles and by annealing at 1023 K. All the samples were homogeneous, and the crystallographic analysis, which was performed by powder and singlecrystal techniques, shows that the four compounds are isotypic and belong to the...

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...

No description

No description