Enhancement of Tc by Sr substitution for Ba in Hg-2212 superconductor

TL;DR

This study demonstrates that substituting Sr for Ba in Hg-2212 superconductors significantly increases the critical temperature (Tc) by about 40 K, with successful synthesis under high-pressure conditions.

Contribution

It provides new insights into Tc enhancement in Hg-2212 superconductors through Sr substitution, including synthesis methods and characterization of the resulting phases.

Findings

Tc increases by about 40 K with Sr substitution

Successful synthesis of Hg-2212 phases up to full Sr replacement

Higher charge carrier density in Sr-substituted compounds

Abstract

The Ba substitution by Sr has been studied in two Hg-2212 series: Hg2(Ba(1-y)Sr(y))2YCu2O8-d and Hg2(Ba(1-y)Sr(y))2(Y0.80Ca0.20)Cu2O8-d. In both series a Tc enhancement of about 40 K is observed when Sr substitutes Ba from y = 0 to y = 1.0. The y = 0 compound of the first series is the non superconducting Hg2Ba2YCu2O8-d prototype. In the second series, this y = 0 compound is already superconducting at 21 K. Indeed the members of this series present a higher charge carrier density in their CuO2 superconducting planes than their homologues of the first series due to the doping introduced by the substitution of 20% of Y by Ca. The compounds of both series were synthesized in high pressure (3.5 GPa) - high temperature (950 - 1050C) conditions. In both cases Sr substitution was successful up to the full replacement of Ba (y = 1.0). The Hg-2212 phases were characterized by XRD, SEM, EDX and a.c. susceptibility.