Superconducting Niobium Stannide (Nb[sub 3]Sn) Films on Metallic Substrates

Niobium stannide, , has been transported from a sintered source material onto various substrates by hydrogen halides in the presence of a temperature gradient. The superconducting transition temperature of the deposited films was found to depend, among other factors, strongly on the separation between the source and the substrate. At large separations, the deposited films were nonstoichiometric due to the differences in reactivities of niobium and tin toward hydrogen halide and the ease of reduction of niobium and tin halides with hydrogen. At small separations, the films deposited on metallic substrates were found to have a superconducting transition temperature of 18°K and a critical current density of up to in magnetic fields of 50 kG.