SUPERCONDUCTING STUDIES IN A-15 PSEUDO-BINARY SYSTEMS

Superconductivity studies have been performed on some A-15 pseudo-binary systems to determine whether low-temperature annealing, conducive to atomic ordering, will markedly raise the superconducting transition temperature. The following systems were examined for this behavior: Nb3GeSingle Bond signNb3Al, Nb3SnSingle Bond signNb3Al, and Nb3GaSingle Bond signNb3Al. Greater attention was devoted to the NbSingle Bond signAlSingle Bond signGe system in view of the recent observation of superconductivity above 20°K in this system. We have also observed transition temperatures approaching 20°K in nearly single phase samples of NbSingle Bond signAlSingle Bond signGe after low-temperature heat treatment at 700°and 800°C. It is suggested that crystallographic long-range ordering is responsible for the high Tc's observed in this system. Attempts to confirm this hypothesis by determining the degree of long-range order were unsuccessful. The other A-15 systems which we investigated also exhibited an increase of Tc with low-temperature heat treatment; however, none exceeded 18°K. © 1969 The American Institute of Physics.