SUPERCONDUCTING TRANSITION TEMPERATURE AND ELECTRONIC STRUCTURE IN THE PSEUDOBINARIES NB3AL-NB3SN AND NB3SN-NB3SB
MASSACHUSETTS INST OF TECH LEXINGTON LINCOLN LAB
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The system Nb3AlySn1-y exhibits complete solid solubility, a positive Seebeck voltage that increases monatomically from 1.8 to over 12 microvoltsdeg. K, and a superconducting transition temperature Tc that has a broad minimum of Tc approx. 15.3K at about y 0.5. The pseudobinary Nb3Sn1-xSbx, on the other hand, contains two phases, each with the A15 structure, in the interval 0.3 x 0.8. Whereas the Seebeck voltage of the low-Sb phase is positive and has a Tc 14K, the high Sb phase has a negative Seebeck voltage and is not superconducting above 4.2K. These properties were interpreted with the aid of a qualitative band-structure scheme. Thus, the rapid drop in Tc to below 4.2K in the system Nb3Sn1-xSbx is believed to be associated with the filling of the bonding, interchain d sub pi bands of the Nb subarray.
- Solid State Physics