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.