Charge transport and thermoelectric properties of P-type Bi2-xSbxTe3 prepared by mechanical alloying and hot pressing

Abstract

Bi2.xSbxTe3 (x = 1.4-1.7) solid solutions were synthesized by mechanical alloying (MA) and consolidated by hot pressing (HP), and their charge transport and thermoelectric properties were examined. The relative densities of the hot-pressed specimens were higher than 96% on average. As the Sb content was increased, the lattice constants decreased, which confirmed that mechanical alloying using a planetary mill was successful in synthesizing solid solutions. The carrier concentration increased with increasing Sb content, and the specimens with x ≥ 1.5 behaved as degenerate semiconductors. All specimens showed p-type conduction, which was confirmed from the positive values of the Seebeck coefficient and the Hall coefficient. The increased Sb content caused a shift in the peak values of the Seebeck coefficient to higher temperatures and enhanced the power factor. As the Sb content increased, the electronic thermal conductivity increased, and the lattice thermal conductivity decreased. Bi0.3Sb1.7Te3 hot-pressed at 698 K exhibited a maximum power factor of 3.4 mWm-1K-2 at 323 K and a low thermal conductivity of 0.8 Wm-1K-1. The maximum dimensionless figure of merit (ZTmax = 1.4) and the average performance (ZTave = 1.2) were obtained at 323 K.