Materials Research on High-Entropy Alloy Superconductors

Abstract

The first purpose of this chapter is materials research on face-centered-cubic (fcc) high-entropy alloy (HEA) superconductors, which have not yet been reported. We have investigated several Nb-containing multicomponent alloys. Although we succeeded in obtaining Nb-containing samples with the dominant fcc phases, no superconducting signals appeared in these samples down to 3 K. The microstructure analyses revealed that all samples were multi-phase, but the existence of several new Nb-containing HEA phases was confirmed in them. The second purpose is the report of materials research on the Mn5Si3-type HEA superconductors. This hexagonal structure offers various intermetallic compounds, which often undergo a superconducting state. The Mn5Si3-type HEA is classified into the multisite HEA, which possesses the high degree of freedom in the materials design and is good platform for studying exotic HEA superconductors. We have successfully found a single-phase Mn5Si3-type HEA, which, however, does not show a superconducting property down to 3 K. The attempt of controlling the valence electron count was not successful.

A novel bulk (Nb,Zr,Pt)67Ti33 high-entropy alloy superconductor: synthesis and structure–property relationship

“…The understanding of suitable mechanisms for superconductivity in HEAs still revolves around valence electron concentration (VEC), which is rather a good approximation for the observed functional behaviour. 15,16 For instance, it has been observed in the case of traditional superconductors that the microstructure has an influence on J c . 7,17,18 Even a slight variation in the grain size or the introduction of secondary phases and precipitates can result in huge variation in superconductivity.…”