Electronic properties of inhomogeneous Bi-Sb-Ni composite alloys

Abstract

It is known that bismuth antimony (Bi-Sb) alloy is not only a good thermoelectric material but also a material which demonstrates some interesting phenomena at low temperatures. We have synthesized composite alloys consisting of the Bi-Sb and magnetic transition metal Ni, and measured the thermoelectric and magnetic properties. The Bi0:88Sb0:12Niy (0 ≤ y ≤ 1.00) alloy ingots were synthesized by fusion method. XRD measurement revealed that the synthesized ingots were inhomogeneous polycrystalline composite. For the lower Ni concentration samples y ≤ 0.10, the thermoelectric and magnetic properties are similar to the host Bi-Sb alloy. The dimensionless thermoelectric figure of merit ZT depends on the Ni concentration y. Observed ZTmax exhibits a maximum value at y ∼ 0.03, due to an enhancement of density of states at EF by Ni doping. For the y = 1.00 sample, on the other hand, we have observed zero resistance below Tc = 4.4 K in the ρ -T curve. Moreover, the magnetization curves below the Tc show large hysteresis. These results indicate that the inhomogeneous Bi-Sb-Ni alloy is a superconductor of the second kind. It is interesting that the composite alloy including only non-superconducting elements and magnetic Ni demonstrates superconductivity.