Thermoelectric properties of Bi2Te3 disk fabricated from rice kernel-like Bi2Te3 powder

Rice kernel (RK)-like bismuth telluride (Bi₂Te₃) crystals were successfully synthesised by microwave-induced plasma heating of Bi and Te powders. Phase and morphology characterisation revealed the presence of the Bi₂Te₃ structure in the shape of RKs. The crystal orientation factor (f value) of RK Bi₂Te₃ powder was larger than that of the RK Bi₂Te₃ hot-pressed disk. A comparison of the f values of both samples suggested that the RK shape has significant influence in reducing the f value after hot processing. The Seebeck coefficient (S), electrical resistivity (ρ) and thermal conductivity (κ) of the RK Bi₂Te₃ disk were determined over the temperature ranging from 323 to 623 K. The S value was negative over the whole temperature range, indicating an n-type thermoelectric RK Bi₂Te₃ disk. The power factor (S²ρ^-1) was the highest at about 1.07 × 10^-3 W/m K² at 323 K and decreased with increasing temperature. The maximum dimensionless figure of merit (ZT) of the RK Bi₂Te₃ disk was 0.26 at about 366 K.