Development of high critical current density in multifilamentary round-wire Bi2Sr2CaCu2O8+x by strong overdoping

TL;DR

This study demonstrates that strong overdoping via low temperature oxygenation significantly enhances the critical current density in multifilamentary round-wire Bi2Sr2CaCu2O8+x superconductors, despite their untextured microstructure.

Contribution

It introduces a method of low temperature oxygenation to achieve high critical current density in round-wire Bi2Sr2CaCu2O8+x superconductors, highlighting the role of overdoping and intergranular connectivity.

Findings

Critical current density doubled to over 1.4x10^5 A/cm^2 at 5 T, 4.2 K.

Overdoping reduces Tc by 12 K to 80 K, improving performance.

Enhanced intergranular connectivity contributes to higher Jc.

Abstract

Bi2Sr2CaCu2O8+x is the only cuprate superconductor that can be made into a round-wire conductor form with a high enough critical current density Jc for applications. Here we show that the Jc(5 T,4.2 K) of such Ag-sheathed filamentary wires can be doubled to more than 1.4x10^5 A/cm^2 by low temperature oxygenation. Careful analysis shows that the improved performance is associated with a 12 K reduction in transition temperature Tc to 80 K and a significant enhancement in intergranular connectivity. In spite of the macroscopically untextured nature of the wire, overdoping is highly effective in producing high Jc values.