Spark plasma sintered Bi0.90Sb0.10 and Bi0.86Sb0.14 alloys and their electrical and thermal transport properties

This work reports the electrical and thermal transport properties of polycrystalline Bi1-xSbx (x=0.10 and 0.14) pellets in the temperature range of 20−300K. The pellets were prepared by spark plasma sintering from ball-milled Bi1-xSbx powders. As semiconductor, the samples displayed n-type conductivity as indicated by the negative sign of the Seebeck coefficient. Semiconducting properties were observed for the Bi0.86Sb0.14 alloy in the entire temperature range of 20−300K, whereas the Bi0.90Sb0.10 alloy exhibited metal-like behavior at low temperatures (20−120K) and semiconducting one at temperatures between 160K and 300K. The metal-like feature of the Bi0.90Sb0.10 sample was attributed to the electron conduction by means of topologically protected surface gapless states, as this material has been reported to be a 3D topological insulator. The temperature dependence of the scattering coefficient and Fermi level shift were analyzed, assuming that prepared alloys are non-degenerate semiconductors in the temperature range where their semiconducting behavior was observed. The carrier thermal conductivity was estimated from the Lorenz number and Wiedemann-Franz law. At high temperature, the thermal energy transport rate is similar for both alloys, whereas at low temperature, it depends on the characteristic electrical behavior of each sample. Interestingly, the polycrystalline nature of our samples seems not affect their electrical and thermal transport properties.