Achieving High Thermoelectric Performance of n-Type Bi₂Te_2.79Se_0.21 Sintered Materials by Hot-Stacked Deformation

Bismuth telluride has been the only commercial thermoelectric candidate, but the n-type sintered material lags well behind the p-type one in the zT value, which severely limits the further development of thermoelectrics. Here, we report a promising technique named hot-stacked deformation to effectively improve the thermoelectric properties of n-type Bi2Te2.79Se0.21 + 0.067 wt % BiCl3 materials based on zone-melting ingots. It is found that a high grain alignment is maintained during the plastic deformation and the carrier concentration is properly optimized owing to the donor-like effect, leading to an enhanced power factor. Moreover, the lattice thermal conductivity is obviously suppressed due to the emerged phonon scattering centers of dense grain boundaries and dislocations. These effects synergistically yield a maximum zT value of 1.38 and an average zTave of 1.18 between 300 and 500 K in the hot-stacked deformed sample, which is approximately 42% higher than those of the zone-melting ingots.