Effects of Pb- or Sn-doping on Low Temperature Thermoelectric Properties of Bi88Sb12

Abstract

(Bi88Sb12)100-xMx (M = Pb, Sn; x = 0.005 to 3) alloys were prepared by direct melting, quenching, and annealing. The X-ray diffraction patterns showed that peaks of Bi-Sb alloy were predominant in all samples. Pb or Sn was distributed almost uniformly in Bi88Sb12, while some segregation was confirmed at grain boundaries when heavily Pb or Sn was involved. Thermoelectric properties were investigated by measuring the Hall coefficient, electrical resistivity, and Seebeck coefficient between 20 K and 300 K. 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 according to annealing process. As a result, the large p-type power factor was obtained with a Pb content of x = 0.005 at low temperatures, and with a Sn content of x = 3 at higher temperatures. These results suggested that preparation of excellent p-type Bi-Sb alloys was possible using heavily Pb- or Sn-doping, quenching, and annealing for homogeneity