Some new superconducting compounds

A number of intermetallic compounds of the form R 2 Ni 17 , R 2 Co 17 and R 2 Fe 17 has been investigated by X-ray diffraction. The structure of these compounds is shown to depend on the size of the rare-earth component and on the temperature. For some of the compounds a low- and a high-temperature modification is observed. For most compounds the type of structure and the lattice constants of each modification are given.

The crystal structures of the rare-earth compounds of the form R2Ni17, R2Co17 and R2Fe17

The crystal structures of the intermetallic compounds in the composition range 89–100% at.% zinc have been investigated for the rare earth (RE)-Zn systems. Five crystal structure types have been found, corresponding to the formulae: REZn13, REZn12, REZn11 and RE2Zn17. The existence of the different structures appears to be closely related to the dimensions of the RE atoms. Eu and Yb behave as divalent elements.

Zinc-rich phases of the rare earth--zinc alloys.

The iron-rich lutetium compound crystallises in a hexagonal structure, space group P63/mmc. By X-ray and neutron diffraction single crystal studies we have shown that its structure does not belong to the ideal Th2Ni17-type as previously proposed. The structure under investigation is established by ordered substitutions occurring in the CaCu5 subcells on two of the three chains of lutetium atoms, parallel to the c -axis. These substitutions lead to an increase of the c parameter which allows for some disordered substitutions on the third chain and the stoichiometry shifts from LuFe8.5 to LuFe9.5.

X-ray and neutron determination of a so-called Th2Ni17-type structure in the lutetium-iron system

Publisher Summary This chapter reviews the synthesis techniques and the crystal chemistry of rare earth-transition metal-indides. It focuses on the phase relations and physical properties, and discusses the structure-property relationships. The crystal chemistry and chemical bonding of the R – T in compounds strongly depend on the composition. The rare earth metal-rich compounds exhibit typical intermetallic structures with relatively large coordination numbers, as found in close packed arrangements. The ternary rare earth metal-transition metal-indium systems contain a vast number of individual intermetallic compounds. The crystallographic data (lattice parameters) of all known indides is discussed in the chapter. The compounds are grouped with respect to the d element component. The chemical and various physical properties of rare earth-transition metal-indides are discussed in this chapter. Most of these indides are light gray in polycrystalline form. Single crystals have metallic luster. Although the rare earth metals are relatively electropositive elements similar to the alkaline earth metals, there is a significant difference in the stability of the ternary compounds.

N. C. Baenziger

Papers

Compounds of thorium with transition metals. II. Systems with iron, cobalt and nickel