Preparation of Bulk and Textured Superconductors

Abstract The preparation and production of bulk High – Temperature Superconductors (HTS) since the discovery is analysed and reported in their development and progress. For the three material groups REBCO (RE: Y, Sm, Gd, Nd, …), BiSCCO (Bi2122, Bi2223), and MgB 2 the processing routes are described and evaluated. While BiSCCO compounds play an important role in the conductor development the REBCO melt texture processes provide large crystalline bulks for magnetic application. Top‐ seed melt growth (TSMG) fabrication methods dominate the bulk production by using single or multiple seeds to prevent unwanted parasitic multi‐ crystalline nucleation. Large single grain bulk fabrication of 50–100 mm requires exact precursor phase preparation of RE123 and RE211 and a temperature/ oxygen‐controlled furnace process. Multiple seeding of large plane bulks, rings and cylinders improves the magnetic properties and ensures an optimum geometry for application. Doping strategy of REBCO bulks is reviewed and the mechanical limitations of REBCO bulks under high trapped field values above 5 Tesla explained. Bulk HTS are characterized by measurements of the critical current density and the maximum magnetic trapped flux density. Physical properties of bulk HTS are given and the magnetic performance of the different REBCO materials (RE= Y, Sm, Nd, Gd) compared in view of applicability.