Low temperature thermoelectric properties of Pb- or Sn-doped Bi-Sb alloys

Pb- or Sn-doped Bi₈₈Sb₁₂ alloys were prepared by direct melting, quenching, and annealing. The Bi-Sb alloy phase was predominant in all samples. Pb or Sn atoms were distributed almost uniformly in Bi₈₈Sb_12, while some segregation was confirmed at the grain boundaries when Pb or Sn was involved heavily. The thermoelectric properties of these doped materials were investigated by measuring the Hall coefficient, electrical resistivity, and Seebeck coefficient between 20 K and 300 K. The Hall and Seebeck coefficients of Pb- or Sn-doped samples were positive at low temperatures, indicating that the doping element acted as an acceptor. Temperatures resulting in positive Hall and Seebeck coefficients further increased with increasing doping amount and with respect to the annealing process. As a result, a large power factor of 1.2 W/mK² could be obtained in the 3-at% Sn-doped sample at 220 K, with a large positive Seebeck coefficient.