Synthesis of Hg-1223 superconductors using a cation-exchange process

The newly developed cation-exchange process was applied to convert Tl2Ba2Ca 2Cu3O10 (Tl-2223) superconductors to HgBa2Ca2Cu3O8+delta (Hg-1223) supercon ductors via Tl-Hg cation-exchange in Hg-vapor at processing temperatures ra nging from 700 to 800 degrees C for 6-24 h. Oxygen annealing process at 350 degrees C for 10 h was followed to optimize the content of oxygen in the H g-1223 samples. The Tl-2223 phase has been successfully converted to Hg-122 3 phase with a negligible amount of non-superconducting impurity phase. T-c values up to 135 K have been obtained in Hg-1223, which are similar to 15 K higher than that of the original Tl-2223 compounds. Since the cation-exch ange process is a kinetic process, it is very promising for fabrication of high-quality Hg-1223 superconductor at large scales. (C) 1999 Elsevier Scie nce B.V. All rights reserved.