F. Merlo

Rare-earth intermediate phases with zinc

Abstract The existence and the structure of the rare earth-zinc intermediate phases in the range 75–88 at.% Zn has been investigated: the compositions MZn3, M3Zn11, MZn4, M13Zn58, MZn5, M3Zn17 and M3Zn22 were examined. A part of the Er-Zn system has been studied by differential thermal analysis. The different types of structure occurring in these intermetallic phases were correlated through the coordination number of the component atoms. The trend of the rare-earth coordination number appears to be related to the existence of ranges of the different phases. In the series of isomorphous compounds, the known, linear dependence of the lattice dimensions upon the rare-earth trivalent ionic radii is confirmed.

CrB-type equiatomic compounds of europium, ytterbium and alkaline-earth metals with Si, Ge, Sn, Pb

Abstract Some MX compounds of Eu and Yb with Si, Ge, Sn, and Pb have been prepared together with the corresponding compounds of the alkaline-earth elements. The crystal structures of YbSi, EuSi, BaSi, EuGe, SrGe, BaGe, EuSn, SrSn, BaSn, and SrPb have been determined. These compounds crystallize with the CrB structure type and their lattice constants, atomic parameters and interatomic distances are reported.

M5X3 intermediate phases formed by Ca, Sr and Ba

Abstract The crystal structures of some M 5 X 3 compounds (M = Ca, Sr, Ba; f,X = element of Group II B, III B, IV B or V B) were determined by single crystal and powder techniques. The phases Ca 5 Zn 3 , Sr 5 Cd 3 , Ca 5 Ga 3 , Sr 5 In 3 , Sr 5 Tl 3 , Sr 5 Sn 3 , Ba 5 Sn 3 and Sr 5 Pb 3 crystallize with the tetragonal Cr 5 B 5 structure type; Ca 5 As 3 , Sr 5 As 3 , Ca 5 Sb 3 and Ba 5 Bi 3 belong to the hexagonal Mn 5 Si 3 type; Sr 5 Bi 3 is isostructural with orthorhombic β-Yb 5 Sb 3 . A survey of the known M 5 X 3 phases formed by the alkaline earth elements is given and the influence of the size factor on the occurrence of the various structural types is discussed.

Rare-earth intermediate phases with cadmium.

Abstract The behaviour of all rare-earth metals with cadmium has been studied for the following compositions: MCd 3 , MCd 4 , M 2 Cd 9~ , MCd 6 and M 2 Cd 17 . The crystal structure of these phases has been determined together with that of ThCd 11 . A survey of all R.E.-Cd intermetallic compounds is given. Structural and geometrical relations among the types of structure occurring are examined.

The gadolinium-cadmium system

Abstract The gadolinium-cadmium equilibrium phase diagram has been established by differential thermal-, chemical-, metallographic- and X-ray analyses. Besides the already known intermediate phases (GdCd, GdCd 2 , GdCd 6 ), three other compounds were found: GdCd 3 (Ni 3 Sn-type), GdCd 4~ (γ-brass type) and Gd 2 Cd 9~ (Gd 13 Zn 58 or Pu 2 Zn 9~ -type). No solid solubility range was observed around the intermediate phases. Only GdCd melts congruently (1170 °C). Cd forms a solid solution with Gd, lowering the α-β transformation of the rare-earth metal from 1238 ° to 725 °C (at ~ 15 at.% Cd). Microhardness, density and magnetic susceptibility were also measured on single phase specimens.

The equilibrium phase diagram of the calcium-lead system and crystal structures of the compounds CaPb, EuPb and YbPb

Abstract The calcium-lead system has been investigated by thermal and X-ray methods. Two compounds melt congruently: Ca2Pb (1203 °C) and CaPb3 (666 °C); two compounds form peritectically : Ca5Pb3 (1127 °C) and CaPb (968 °C). Two eutectics occur, at 90.5 at.% Ca (750 °C) and 36.5 at.% Ca (638 °C), respectively. The crystal structures of Ca2Pb, Ca5Pb3 and CaPb3 were confirmed. The compound CaPb was found to crystallize with the AuCu I-type structure ( a = 5.118 A ; c = 4.491 A ). The same structure type was found for the phases EuPb ( a = 5.226 A ; c = 4.586 A ) and YbPb ( a = 5.085 A ; c = 4.443 A ), in which Eu and Yb behave as divalent elements similar to the alkaline earths.

Re-examination of the CaGa system and crystal structure of CaGa4, a monoclinic distortion of the BaAl4 type

Abstract The gallium-rich region of the CaGa system (64.9 – 84.6 at.% Ga) was re-examined by X-ray methods. In addition to the CaGa 2 phase with the CaIn 2 structure type, another phase, CaGa 2 + x , was found in a limited homogeneity range, being 0.1 ⩽ x ⩽ 0.4, with crystal structure derived from the AlB 2 type. The mechanism of solid solubility formation was clarified by single crystal refinement. The new phase Ca 3 Ga 8 was identified by powder diffraction data as isotypic with Eu 3 Ga 8 . The structure of CaGa 4 , determined by single crystal methods, can be described as a new monoclinic distortion of the BaAl 4 type, related to the low temperature form of CaAl 4 . Crystal data of the nine intermediate phases present in the CaGa system are given and a revised form of the phase diagram is proposed.

The strontium-aluminium and barium-aluminium systems

Abstract The strontium-aluminium and barium-aluminium systems have been examined by thermal, micrographic and X-ray methods. Compounds corresponding to the following compositions were observed: Sr 3 Al 2 (666 °C), SrAl 2 (936 °C), SrAl 4 (1040 °C); BaAl (730 °C), BaAl 2 (914 °C), BaAl 4 (1104 °C). Only SrAl 4 and BaAl 4 melt congruently. Eutectic points occur at 81.75 at.% Sr (590 °C) and at 71.5 at.% Ba (538 °C) in the respective systems. Preliminary structural results on the intermediate phases are reported. The alloying behaviour of aluminium with the alkaline-earth metals is compared with that of aluminium with other groups of more electropositive metals.

The calcium-mercury system

Abstract The calcium-mercury system has been investigated using thermal, micrographic and X-ray methods. Three compounds melt congruently: CaHg (961 °C), CaHg2 (746 °C) and Ca3Hg (523 °C). Six other compounds form peritectically: Ca2Hg(530 °C),Ca5Hg3(587 °C), Ca3Hg2(660 °C), CaHg3 (570 °C), CaHg3.6(264 °C) and CaHgx with 7 The crystal structures of all compounds except CaHgx were determined.

The strontium-mercury system

Abstract The strontium-mercury system has been investigated using thermal, micrographic and X-ray methods. Two compounds melt congruently: SrHg(850 °C) and SrHg 2 (772 °C). Eight other compounds form by peritectic reactions: Sr 3 Hg(458 °C), Sr 2 Hg(478 °C), Sr 3 Hg 2 (545 °C), SrHg 3 (512 °C), SrHg 3.6 (481 °C), Sr 2 Hg 9~ (427 °C), SrHg 11 (289 °C) and SrHg x ( x ≅ 13, 62 °C). Two eutectics occur at 82.0 at.% Sr(442 °C) and at 40.5 at.% Sr(694 °C). No solid-solubility range was observed around the intermediate phases. The crystal structures of all compounds except Sr 2 Hg and SrHg x were determined.