Effect of cationic size in Hg(Tl/Bi)Ba2Ca2Cu3O8+δ on superconducting and microstructural characteristics

Abstract

In this paper we have reported investigations on the effect of simultaneous substitution of Bi and Tl at the Hg site in the oxygen deficient HgOδ layer of HgBa2Ca2Cu3O8+δ cuprate superconductor. Bulk polycrystalline samples have been prepared by the two-step solid state reaction process (precursor route). It has been observed that the as grown HgBi0.2-xTlxBa2Ca2 Cu3O8+δ (with x = 0.00, 0.05, 0.10, 0.15, 0.20) corresponds to the 1223 phase. It has been found that the Tc varies with the average cationic size of the dopant cations. The optimum Tc of ∼131 K has been found for the composition HgBi0.15Tl0.05Ba2Ca2Cu3 O8+δ. This composition leads to the average dopant cation size of ∼1.108 Å which is very close to the size of Hg2+ (∼1.11 Å). The microstructure for HgBi0.15Tl0.05Ba2Ca2Cu3 O8+δ has been found to be most dense and this phase exhibits the highest stability. The Jc of the optimum material HgBi0.15Tl0.05Ba2Ca2Cu3 O8+δ is found to be ∼1.29 × 103 A/cm2 at 77 K.