Synthesis of high-entropy-alloy-type superconductors (Fe,Co,Ni,Rh,Ir)Zr2 with tunable transition temperature

Abstract

We report on the synthesis and superconductivity of high-entropy-alloy-type (HEA-type) compounds TrZr2 (Tr = Fe, Co, Ni, Rh, Ir), in which the Tr site satisfies the criterion of HEA. Polycrystalline samples of HEA-type TrZr2 with four different compositions at the Tr site were synthesized by arc melting method. The phase purity and crystal structure were examined by Rietveld refinement of X-ray diffraction profile. It has been confirmed that the obtained samples have a CuAl2-type tetragonal structure. From analyses of elemental composition and mixing entropy at the Tr site, the HEA state for the Tr site was confirmed. The physical properties of obtained samples were characterized by electrical resistivity and magnetization measurements. All the samples show bulk superconductivity with various transition temperature (Tc). The Tc varied according to the compositions and showed correlations with the lattice constant c and Tr-Zr bond lengths. Introduction of an HEA site in TrZr2 is useful to achieve systematic tuning of Tc with a wide temperature range, which would be a merit for superconductivity application.

16 pages, 5 figures, SI

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• Superconductivity near the Mott-Ioffe-Regel limit in the high-entropy alloy superconductor (ScZrNb)${}_{1-x}$(RhPd)${}_x$ with a CsCl-type lattice
• Anomalous thermal expansion in a CuAl2-type superconductor CoZr2
• Sign change in c-axis thermal expansion and lattice collapse by Ni substitution in Co1-xNixZr2 superconductors
• Improvement of local critical current density of REBa2Cu3O7-d by the increase in configurational entropy of mixing at the RE site
• Superconductivity of high-entropy-alloy-type transition-metal zirconide (Fe,Co,Ni,Cu,Ga)Zr2
• Elastic properties of a Sc-Zr-Nb-Ta-Rh-Pd high-entropy alloy superconductor
• Atomic, electronic, and superconducting properties of Zr${}_2$Ir compound
• Estimation of Grüneisen parameter of high-entropy-alloy-type functional materials