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Thermoelectric properties of the hot-pressed Bi2(Te0.85Se0.15)3 alloy were investigated with the addition of BN powders as phonon scattering centers. The Seebeck coefficient and electrical resistivity of the alloy increased as the volume fraction of BN increased. Although the thermal conductivity of the alloy decreased as the volume fraction of BN increased due to the reduction of Kel, the lattice thermal conductivity varied little. The figure-of-merit of the alloys, 1.6×l0-3/K without the addition of BN, decreased as the volume fraction of BN increased because the increment of the electrical resistivity was much larger than the decrement of the thermal conductivity due to grain refinement.

Thermoelectric properties of the 0.05 wt.% SbI3-doped n-type Bi2(Teo.95Seo.o5)3 alloy, fabricated by hot pressing at temperatures ranging from 350°C to 550°C, were characterized. The electron concentration of the alloy decreased as the hot pressing temperature increased due to the annealing-out of the excess Te vacancies. When hot pressed at 350°C, a figure-of-merit of 0.75x10-3/K was obtained due to the low Seebeck coefficient of -145 µV/K and relatively high electrical resistivity of 2.05 mΩ-cm. Upon increasing the hot pressing temperature, however, the figure-of-merit was improved mainly due to the increase of the Seebeck coefficient. A maximum figure-of-merit of 2.1x10-3/K was obtained by hot pressing at 550°C.

P-type (Bi0.25Sb0.75)2Te3 powders were fabricated by melting/grinding and mechanical alloying processes. Thermoelectric properties of the hot-pressed (Bi0.25Sb0.75)2Te3 were characterized with the powder processing method, powder size, hot pressing temperature, and the amount of excess-Te dopant. Specimens fabricated by melting/grinding exhibited lower Seebeck coefficient, lower electrical resistivity and higher thermal conductivity, compared to the specimens prepared by mechanical alloying. 3 wt.% excess Te-doped (Bi0.25Sb0.75)2 Te3, fabricated by melting/grinding and hot pressing at 550°C, exhibited a figure-merit of 3.2 x 10-3/K. For 1 wt.% excess Te-doped specimen prepared by mechanical alloying and hot pressing at 550°C, a figure-merit of 3.05 x 10-3/K was obtained.