Ferropnictide superconductors, i.e., superconductors that contain Fe and As, have superconducting transition temperatures (Tc) up to 56 K and high upper critical fields (Hc2) over 100 Telsa. The high Hc2 means these materials could be used in very high field magnets. Previous studies suggested that polycrystalline samples of these materials could not carry a large superconducting current because grain boundaries reduce the critical current density (Jc). Surprisingly, new results find that the opposite is true for wire made from (Ba0.6K0.4) Fe2As2.
Synthesized polycrystalline wires and bulk material using high-energy ball milling and high-pressure heat treatment were produced. The critical current flowed over the whole sample at values more than 10 times higher than in any previously reported ferropnictide wire.
The exciting and surprising result is that high Jc occurs over the whole sample at almost-application-ready Jc values, in spite of having a very high density of grain boundaries due to the small (~100 nm) grain size and lack of texture.
Nature Materials - High intergrain critical current density in ﬁne-grain (Ba0.6K0.4)Fe2As2 wires and bulks (3 pages)
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