Influence of simultaneous doping of Sb & Pb on phase formation, superconducting and microstructural characteristics of HgBa2Ca2Cu3O8+\delta

TL;DR

This study investigates how simultaneous doping of Sb and Pb affects the phase formation, microstructure, and superconducting properties of HgBa2Ca2Cu3O8+b4, revealing microstructural features linked to enhanced current density.

Contribution

It provides new insights into how Sb and Pb co-doping influences phase purity, microstructure, and superconducting performance in Hg-based cuprates.

Findings

Simultaneous Sb and Pb doping promotes Hg-1223 phase formation.

Large spiral-like grains correlate with higher transport current density.

The compound with x=0.15 shows the highest Jct (~1.85 x 10^3 A/cm^2) at 77K.

Abstract

We report systematic studies of structural, microstructural and transport properties of (Hg_0.80 Sb_0.2-x Pb_x)Ba_2 Ca_2 Cu_3O_8+\delta (where x = 0.0, 0.05, 0.1, 0.15, 0.2) compounds. Bulk polycrystalline samples have been prepared by two-step solid-state reaction route at ambient pressure. It has been observed that simultaneous substitution of Sb and Pb at Hg site in oxygen deficient HgO_\delta layer of HgBa2Ca2Cu3O8+\delta cuprate high-Tc superconductor leads to the formation of Hg-1223 as the dominant phase. Microstructural investigations of the as grown samples employing scanning electron microscopy reveal single crystal like large grains embodying spiral like features. Superconducting properties particularly transport current density (Jct) have been found to be sensitive to these microstructural features. As for example (Hg0.80Sb0.05Pb0.15)Ba2Ca2Cu3O8+\delta compound which exhibits single crystal like large grains (~ 50 micrometer) and appears to result through spiral growth mechanism, shows highest Jct (~ 1.85 x 103 A/cm2) at 77K. A possible mechanism for the generation of spiral like features and correlation between microstructural features and superconducting properties have been put forward.