Thermoelectric properties of n-type (Bi₂Se₃)_x(Bi₂Te₃)_1-x prepared by bulk mechanical alloying and hot pressing

Starting from element Bi, Se and Te granules, n-type (Bi₂Se₃)_x(Bi₂Te₃)_1-x with different chemical composition (x = 0.025, 0.05, 0.075, 0.10 and 0.15) were prepared via bulk mechanical alloying (BMA) and hot pressing (HP). Effects of chemical composition, doping content and annealing on thermoelectric properties were reported. The range x≤0.050 is more favorable than other chemical compositions for the thermoelectric properties of BMAed (Bi₂Se₃)_x(Bi₂Te₃)_1-x. When doping with SbI₃, both the electrical resistivity and the Seebeck coefficient of (Bi₂Se₃)_0.05(Bi₂Te₃)_0.95 decrease, thus resulting in no improvement of the figure of merit. On the other hand, annealing the as-HPed (Bi₂Se₃)_0.05(Bi₂Te₃)_0.95 a sufficiently long time is helpful to improve thermoelectric properties, and the maximum figure of merit of (Bi₂Se₃)_0.05(Bi₂Te₃)_0.95 is 2.31×10^-3 /K.