Thermoelectric Properties of Bi-Sb-Te Prepared by Mechanical Alloying and the Vertical Bridgman Method

抄録

Bi_0.5Sb_1.5Te_3.0+x compounds with varying tellurium content (x=−0.10∼0.10) were prepared using mechanical alloying (MA) and the vertical Bridgman method (VBM), and compared their Hall coefficients, electrical resistivities and Seebeck coefficients at room temperature. In changing the tellurium content, it was possible to change the carrier concentration from 7.99×10²⁴ to 1.52×10²⁶m⁻³ for −0.10 < x < 0.00. In contrast, the carrier concentration was almost constant at 1.0×10²⁵m⁻³ for 0.00 < x < 0.10. For samples with the same composition, it was observed that the carrier concentration of the VBM sample was approximately four times higher than that of the MA sample. The Seebeck coefficients for the two methods corresponded well with the relative carrier concentration, although the electrical resistivities of the VBM samples were found to vary because of preferred orientation. The maximum power factors for the MA and VBM samples were 3.52×10⁻³Wm⁻¹K⁻² at 1.23×10²⁵m⁻³ (x=0.03), and 3.52×10⁻³Wm⁻¹K⁻² at 3.18×10²⁵m⁻³ (x=0.00135), respectively. These results indicate that the difference in the carrier concentrations for two methods can be explained by the tellurium deficiency in samples prepared using the VBM.