Influence of P on Microstructure and Thermoelectric Property of Sintered (Bi_0.2Sb_0.8)₂Te₃ Alloy

Abstract

A combination of mechanical alloying and pulse discharge sintering (MA-PDS) was employed to synthesize the bulk (Bi_0.2Sb_0.8)₂Te₃ alloys with the P addition up to 2.0 mass%. The effect of P on the microstructure and thermoelectric performance of the compacts were investigated. The added P exists in the alloyed powders and compacts in the form of second phase particles. The dispersed P particles were found to decrease the size of (Bi, Sb)₂Te₃ crystallites and inhibit the densification of the alloyed powders. When the P content ≥1.0 mass%, (Bi_0.2Sb_0.8)₂Te₃/P nanocomposites were developed by the MA-PDS process. Inclusion of a small fraction of P (≤0.1 mass%) is harmless to the thermoelectric performance of the p-type (Bi_0.2Sb_0.8)₂Te₃ alloy. In the samples with high P contents, in particular, ≥1.0 mass%, however, the increase in the electrical resistivity is much greater than the decrease in the thermal conductivity, finally giving rise to degradation of the room-temperature figure of merit.