We fabricate fine (<20 μm) powders of Bi0.5Sb1.5Te3 alloys using a large-scale production method and subsequently consolidate them at temperatures of 573, 623, and 673 K using a spark plasma sintering process. The microstructure, mechanical properties, and thermoelectric properties are investigated for each sintering temperature. The microstructural features of both the powders and bulks are characterized by scanning electron microscopy, and the crystal structures are analyzed by X-ray diffraction analysis. The grain size increases with increasing sintering temperature from 573 to 673 K. In addition, the mechanical properties increase significantly with decreasing sintering temperature owing to an increase in grain boundaries. The results indicate that the electrical conductivity and Seebeck coefficient (217 μV/K) of the sample sintered at 673 K increase simultaneously owing to decreased carrier concentration and increased mobility. As a result, a high ZT value of 0.92 at 300 K is achieved. According to the results, a sintering temperature of 673 K is preferable for consolidation of fine (<20 μm) powders.

The p-type Te functional gradient material (FGM) was fabricated by hot-pressing the mechanically alloyed and the 0.5 at% powders. Also, the n-type FGM was processed by hot-pressing the mechanically alloyed and the 0.3 wt% Bi-doped PbTe powders. With larger than , the p-type FGM exhibited larger thermoelectric output power than those of the and the 0.5 at% alloys. For the n-type FGM, the thermoelectric output power superior to those of the and the 0.3 wt% Bi-doped PbTe was predicted at larger than .