SUPERCONDUCTIVITY IN THE NIOBIUM-TIN SYSTEM,
Abstract
The critical current, temperature, and field of compositeNb-Sn wires and sintered Nb-Sn powder compacts of varying composition were found to depend on the properties and distribution of the phases present after heat treating at temperatures up to 1500 C. A voltage drop was used to judge the onset of normal behavior in specimens carrying up to 100,000 amps/sq. cm which were tested in fields up to 90,000 gauss and at temperatures ranging from 4.2 to 1.95 K. The temperature ranges of stability for Nb3Sn, Nb3Sn2, Nb2Sn3 and a terminal solid solution of Sn in Nb were determined and a tentative phase diagram proposed. The transition temperature for Nb2Sn3 varies from 3.4 to 2.4 K. The Nb solid solution has a critical field of 10,500 gauss and a critical current density of 4,400 amps/sq. cm at 2.2 K in a 10,000 gauss field. A systematic decrease in critical current density occurs with increasing heat treating temperature for composite wires heat treated at temperatures above 1000 C for 6 minutes. This decrease appears to be associated with a decrease in interstitial content in the Nb3Sn, or the annealing out of chemical inhomogeneities that may be responsible for high-field, high-current superconductivity. (Author)
Document Details
- Document Type
- Technical Report
- Publication Date
- May 01, 1963
- Accession Number
- AD0415847
Entities
People
- Ronald Edward Enstrom
Organizations
- Massachusetts Institute of Technology