Synthesis and thermoelectric properties of Zn₄Sb ₃/Bi_0.5Sb_1.5Te₃ bulk nanocomposites

The bulk nanocomposites f(Zn₄Sb₃)/ Bi _0.5Sb_1.5Te₃ (f = 0, 5, 10 and 15 vol.%) were prepared, and their thermoelectric properties were investigated at temperatures from 300 to 650 K. The results of Xray diffraction (XRD) and field emission scanning electron microscopy (FE-SEM) showed that the nanometer-sized Zn ₄Sb₃ particles were dispersed homogeneously in Bi _0.5Sb_1.5Te₃ matrix. Transport property measurements indicated that the resistivity and Seebeck coefficient of the composite samples f(Zn₄Sb₃)/ Bi_0.5Sb _1.5Te₃ (f = 0, 5, 10 and 15 vol.%) decreased with increasing Zn₄Sb₃ content due to the increase in carrier concentration. Experiments also showed that thermal conductivity of f(Zn ₄Sb₃)/ Bi_0.5Sb_1.5Te₃ decreased monotonically with increasing f owing to enhanced phonon scattering by the dispersed Zn₄Sb₃ nanoparticles and the phase boundaries in the matrix. Among the samples studied, 15 vol.% (Zn ₄Sb₃)/ Bi_0.5Sb_1.5Te₃ exhibited the largest power factor (25μW/cmK² at ∼300 K) that was 2.5 times larger than that of Bi_0.5Sb_1.5Te ₃; correspondingly, its figure of merit (ZT = 0.6 at ∼300 K) was about three times larger than that of Bi_0.5Sb_1.5Te ₃, indicating that the thermoelectric properties of Bi _0.5Sb_1.5Te₃ can be enhanced effectively by the dispersion of nanometer-sized Zn₄Sb₃.