Effect of cationic size in Hg(TI/Bi)Ba2Ca2Cu3O8+delta superconducting and microstructural characteristics

In this paper we have reported investigations on the effect of simultaneous substitution of Bi and TI at the Hg site in the oxygen deficient HgOdelta layer of HgBa2Ca2Cu3O8+delta cuprate superconductor. Bulk polycrystalline s amples have been prepared by the two-step solid state reaction process (pre cursor route). It has been observed that the as grown HgBi0.2-xTIxBa2Ca2Cu3 O8+delta (with x = 0.00, 0.05, 0.10, 0.15, 0.20) corresponds to the 1223 ph ase. It has been found that the T-c varies with the average cationic size < R-d> of the dopant cations. The optimum T-c of similar to 131 K has been fo und for the composition HgBi0.15TI0.05Ba2Ca2Cu3O8+delta. This composition l eads to the average dopant cation size of similar to1.108 Angstrom which is very close to the size of Hg2+ (similar to1.11 Angstrom). The microstructu re for HgBi0.15TI0.05Ba2Ca2Cu3O8+delta has been found to be most dense and this phase exhibits the highest stability. The J(c) of the optimum material HgBi0.15TI0.05Ba2Ca2Cu3O8+delta is found to be similar to1.29 x 10(3) A/cm (2) at 77 K.