Thermoelectric properties of Ge-doped Bi85Sb15 alloys at low temperatures

• Bi85Sb15−xGex alloys were synthesised by a relatively easy powder-based process.
• Increasing Ge doping changes the magnitude or sign of the Seebeck coefficient.
• A maximum ZT value of 0.07 was obtained at 140 K.

Bulk polycrystalline Bi85Sb15−xGex (x=0, 0.5, 1, 1.5, 2) composites were prepared by mechanical alloying followed by pressureless sintering. The thermoelectric properties were studied in the temperature range of 77–300 K. The results indicate that increasing the Ge concentration causes the Seebeck coefficient to change sign from negative to positive. Moreover, it is found that the maximum value of the Seebeck coefficient can be precisely controlled with the Ge concentration. The maximum dimensionless figure of merit reaches 0.07 at 140 K. These results suggest that the preparation of p-type Bi–Sb alloys is possible by using the Ge-doping approach.

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