The synthesis, characterization and effect of Ag doping on the transition temperature and critical current density of Hg1-xPbxBa2Ca2Cu3O8+delta (0.1 <= x <= 0.5) HTSC tapes

Pb-doped Hg-1223 HTSC tapes have been synthesized by annealing the precurso r tape (fabricated by doctor blade tape casting technique) in the environme nt of Hg(Pb) vapor in an evacuated sealed quartz tube at 870 degrees C for 8 h. The HTSC tapes with x ranging between 0.1 and 0.5 exhibit high tempera ture superconductivity at temperature falling in the range from 110-119 K. The tape sample with optimum doping of Pb-0.35 has a highest T-c and J(c) o f similar to 119 K and 5.1 X 10(3) A/cm(2) With the slight addition of Ag i nto optimally Pb-doped Hg-1223 tape sample, T-c has been found to increase slightly but there is significant enhancement of J(c) up to a optimum conce ntration of Ag. The highest T-c of similar to 123 K and highest J(c) of sim ilar to 2.5 x 10(4) A/cm(2) is obtained for the tape sample having Ag conce ntration of 0.2, i.e., (Ag-0.2), being an order of magnitude higher than th e J(c) of Ag free optimally Pb-doped Hg-1223 tape samples. J(c) has been ob served to decrease with Ag content higher than 0.2. This decrease in J(c) h as been attributed to the formation of Ag-Hg amalgam, due to the reaction o f Hg with Ag. (C) 1999 Published by Elsevier Science B.V. All rights reserv ed.