Influence of alloying on the superconducting transition temperature of La3In

The effects of heat treatment and stoichiometry on the superconducting transition temperature Tsub(c) of La3In were studied. The mechanical properties indicate that La3In is surprisingly ductile for an intermetallic compound. The effects on Tsub(c) of alloying by substituting Ca, Sc, Y, Yb, Lu and Th for La, and Mg, Al, Mn, Zn, Ga, Ge, Cd, Sn, Tl, Pb and Bi for In were investigated. Additions of interstitial non-metallic elements (H, B, C, N, O and Si) were also studied. Almost all impurity elements lower Tsub(c). For La subsitutions dTsub(c)/dn was found to be proportional to the square of the difference in the radii (rsub(R)-rsub(La)) but the change in the electron concentration had little if any effect on Tsub(c). For In substitutions the size of the impurity atom had only a minor influence on dTsub(c)/dn, while an increase in the electron concentration accelerated the depression of Tsub(c). Solid solubility limits were also deduced when sufficient data were available. (Auth.)