Thermoelectric Properties of Cu-Doped n-Type Bi2Te2.85Se0.15 Prepared by Liquid Phase Growth Using a Sliding Boat

N -type Bi 2 Te 2.85 Se 0.15 thermoelectric materials were prepared by liquid phase growth (LPG) using a sliding boat, a simple and short fabrication process for Bi 2 Te 3 -related materials. Cu was selected as a donor dopant, and its effect on thermoelectric properties was investigated. Thick sheets and bars of Cu x Bi 2 Te 2.85 Se 0.15 ( x =0–0.25) of 1–2mm in thickness were obtained using the process. X-ray diffraction patterns and scanning electron micrographs showed that the in-plane direction tended to correspond to the hexagonal c -plane, which is the preferred direction for thermoelectric conversion. Cu-doping was effective in controlling conduction type and carrier (electron) concentration. The conduction type was p -type for undoped Bi 2 Te 2.85 Se 0.15 and became n -type after Cu-doping. The Hall carrier concentration was increased by Cu-doping. Small resistivity was achieved in Cu 0.02 Bi 2 Te 2.85 Se 0.15 owing to an optimized amount of Cu-doping and high crystal orientation. As a result, the maximum power factor near 310K for Cu 0.02 Bi 2 Te 2.85 Se 0.15 was approximately 4×10 −3 W/K 2 m and had good reproducibility. Furthermore, the thermal stability of Cu 0.02 Bi 2 Te 2.85 Se 0.15 was also confirmed by thermal cycling measurements of electrical resistivity. Thus, n -type Bi 2 Te 2.85 Se 0.15 with a large power factor was prepared using the present LPG process.