ICT2014 Abstracts

Bi₂Te₃-based compounds exhibit an anisotropic thermoelectric property. Thermoelectric figure of merit is better in the hexagonal c-plane than to direction along the c-axis.Liquid phase growth (LPG) using a sliding boat is a simple, easy, and short process for preparation of Bi₂Te₃-related materials with high c-plane orientation. We reported that a large power factor of 4.4W/K²m at 300 K was obtained in p-type Bi_0.5Sb_1.5Te₃, by this LPG process.

In the present study, this LPG method was applied to Cu-doped n-type Bi-Te-Se based materials. Thick sheets and bars of Cu_xBi₂Te_2.85Se_0.15 (x=0–0.25) of 1 to 2 mm in thickness were prepared and n-type thermoelectric properties and its stability and reproducibility were investigated. The materials obtained by LPG were coarse grained poly crystals and the in-plane direction tended to correspond to the hexagonal c-plane, which is the preferred direction for thermoelectric conversion. A small resistivity was achieved in Cu_0.02Bi₂Te_2.85Se_0.15 owing to an optimized amount of Cu-doping and high crystal orientation. As a result, the maximum power factor more than 4 × 10^–3 W/K²m was obtained near room temperature for Cu_0.02Bi₂Te_2.85Se_0.15 with good reproducibility. 　Moreover, good thermal and aging stability were also confirmed. Thus, the present simple and short-time LPG process enabled the preparation of Cu-doped n-type Bi₂Te_2.85Se_0.15 having a large power factor and stable thermoelectric property when the doping concentration was properly selected.