Elongate Bi-based superconductors made by freeze dried conducting powders

A superconducting tape or wire with a longitudinally extending outer layer of Ag or its alloys defining an inner region, an area of Ag or its alloys in said inner region extending longitudinally of said tape or wire separated from said outer layer of metal by freeze dried superconducting material. The inner Ag area may be a rod, a tube or a number of wires. The superconductor material is preferably B-2223.