NbTi

NbTi is a ductile binary alloy of niobium and titanium, widely used as a superconducting material in magnets. It remains superconducting below about 9.2 K and is a Type II superconductor with an upper critical field Hc2 on the order of 10–15 T at cryogenic temperatures, depending on composition and temperature.

The typical composition is Nb-47Ti (about 47 atomic percent Ti; balance Nb), though the exact ratio varies to optimize performance. NbTi is manufactured as multifilamentary wires with NbTi filaments embedded in a copper matrix for stabilization and heat transfer; some wires use a bronze or copper-stabilized route.

NbTi is among the most ductile and easily drawn superconductors, enabling long magnets with high current densities at 4 K. Its critical current density Jc declines with magnetic field, and practical high-field limits are set by Hc2 rather than Tc. The material is relatively inexpensive and robust for cryogenic operation.

Applications include magnets for magnetic resonance imaging (MRI) and nuclear magnetic resonance (NMR), as well as dipole and quadrupole magnets in several particle accelerators. NbTi remains a baseline technology for many applications due to manufacturability and cost, with higher-field requirements often met instead by Nb3Sn or other superconductors.