Research development and prospects of superconducting materials in China

Great progress in research and development of high-T_c superconducting materials has been made in China since 1987. A new technique, the powder melting process (PMP), has been developed to prepare high-J_c (exceeding 10⁵ A/cm² at 77 K and 1 T) YBCO bulks. Effective pinning centers such as dispersively distributed fine Y₂BaCuO₅ inclusions, stacking faults and dislocations can be introduced into Y-system superconductors by the PMP method. Large single-domain YBCO bulks with high performance have been fabricated in a small-scale production in China. Some demonstration models such as the magnetic levitation train and flywheels have been constructed using these bulk materials. Much work has been carried out to understand the mechanism of formation and texturization of Bi-2223 phase in the Ag-sheathed tapes. Based on understanding of the 2223 phase formation mechanism, high J_c multifilamentary Bi-2223/Ag (Ag alloy) tapes have been fabricated by the modified powder-in-tube (PIT) method. An HTSC cable with capacity of 1 kA constructed by using Bi-2223 has been successfully demonstrated. In addition Bi-2223 current leads with critical current more than 1 kA have been fabricated and used in the superconducting magnets cooled by a G-M refrigerator. In the future, there are some projects to promote the electric application of HTSC materials such as cables, MRI, transformer, and fault current limiter etc.