Improvement of critical current density of RE Ba 2 Cu 3 O 7-δ by increase in configurational entropy of mixing

Abstract

RE Ba 2 Cu 3 O 7- δ ( RE 123, RE : rare earth) is one of the high-temperature superconductors with a transition temperature ( T c ) exceeding 90 K. Because of its high- T c and large critical current density ( J c ) under magnetic fields, RE 123 superconductors have been expected to play a key role in superconductivity application. To accelerate application researches on RE 123-based devices, further improvements of J c characteristics have been desired. In this study, we investigated the effects of high-entropy alloying at the RE site on the superconducting properties, through the measurements of local (intra-grain) J c ( J c local ) by a remanent magnetization method. We found that J c local shows a trend to be improved when four or five RE elements are mixed at the RE site, which results in high configurational entropy of mixing (Δ S mix ). All samples exhibited an order of few MA cm −2 which is a criterion for practical application and the highest J c local resulted in a value of around 7.0 MA cm −2 at T = 2.0 K. Because high-entropy alloying can improve J c local of RE 123 superconductors, our entropy-engineering strategy introduced here would be useful for the development of RE 123 superconducting materials available under high magnetic fields.