Ternary Superconducting Chalcogenides

Two new structural groups of ternary superconductors (not ternary solid solutions of binary phases), noncubic at room temperature, have recently been reported. They are discussed briefly here because they are the first known chalcogenide phases exhibiting relatively high 7. The critical temperatures, however, are under 14°K. 

Ti3S4 structure. They are unstable between 77°K and 600°K. When they are held for several hours at room temperature their transition temperature drops by a few degrees. Subsequent annealing at 900°C and quenching restores bulk superconductivity. Thus this is another example of the existence of metastability or a tendency toward structural instability as a precursor to the existence of high-7 superconductivity. 

The second structural group is composed of compounds of the form Mo. A S, where A = Cu, Zn, Mg, Ag, Cd, Sn, or Pb. These compounds were first synthesized by Cheverel et and are 

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A class of metal cluster superconductors of particular Interest consists of ternary molybdenum chalcogenides, conmonly known as the Chevrel phases (13). These phases were the first type of superconducting ternary system found to have relatively high critical temperatures and exhibited the highest known critical magnetic fields (Hc2 before discovery of the copper oxide... 

Chevrel, R. Sergent, M. (1982). Chemistry and Structure of Ternary Molybdenum Chalcogenides. in Topics in Current Physics "Superconductivity in Ternary Compounds 1" Vol. 32, 5 - 86. Editors 0. Fischer and M.B. Maple. Berlin Springer. 

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