Chevrel phase high field superconductors: Metallurgy, fabrication, and applications

The results of investigations of ternary molybdenum chalcogenides indicate that these compounds might be model substances for a systemmatic study of the relationships between structural parameters and physical properties. In the first investigations, the observation that by increasing Cu concentration the intracluster Mo-Mo distances decrease indicates that the insertion of M atoms might constitute an influence on the electronic structure of the host lattice Mo6X8 and can be responsible for important variations of some physical properties. The compounds superconduct at critical temperatures, have high resistivities in the normal state, and unusual lattice properties. A model is developed in which substitutions (of M2+ for M3+ for example) have a minor effect on the crystal structure but a large influence on the electronic properties in so far as the charge transfer leads to a change of position of the Fermi level, and d /SUB Mo-Mo/ intercluster leads to an increased width of the d-band. The extremely high critical field of these compounds suggests them as serious candidates for technical applications. Finally, the preparation, characterization, and some physical properties of new compounds proceeding from the linear condensation of the octahedral Mo6 clusters are given