Superconductivity of powder-in-tube MgB₂wires

Abstract

A new class of `powder-in-tube' Mg-B superconducting conductors has been prepared using two different methods: an in situ technique where an Mg + 2B mixture was used as a central conductor core and reacted in situ to form MgB2, and an ex situ technique where fully reacted MgB2 powder was used to fill the metal tube. Conductors were prepared using silver, copper and bimetallic silver/stainless steel tubes. Wires manufactured by the in situ technique, diffusing Mg to B particles experienced ~25.5% decrease in density from the initial value after cold deformation, due to the phase transformation from Mg + 2(β-B)→MgB2 all with hexagonal structure.