Enhanced thermoelectric performance of n-type bismuth-telluridebased alloys via In alloying and hot deformation for mid-temperature power generation

Bismuth telluride-based alloys are the most widely used commercial thermoelectric(TE)material for room temperature refrigeration.Here,we successfully shift up the optimum figure of merit of n-type bismuth-telluride-based TE materials for mid-temperature power generation.SbI_(3)doping is used to regulate the carrier concentration and Indium alloying to increase the bandgap,suppressing the detrimental bipolar conduction in the mid-temperature range.The lattice thermal conductivity is significantly reduced due to the multiscale microstructures induced via hot deformation.As a result,a peak zT of~1.1 was attained at 625 K for Bi_(1.85)In_(0.15)Te_(2)Se+0.25 wt%SbI_(3)alloy after hot deformation,showing a great application prospect of this alloy in mid-temperature TE power generation.

Mid-temperature thermoelectric performance of zone-melted Sb_(2)(Te,Se)_(3) alloys near phase transition boundary

(Bi,Sb)_(2)(Te,Se)_(3) alloys are widely used commercial thermoelectric(TE)materials for solid-state refrigeration around room temperature.The composition-induced structural phase transition could be realized by varying the compositions in these alloys,which may largely alter the electronic structure and phonon dispersion.Among them,the Se-alloyed Sb_(2)Te_(3) accompanied with structural transition is seldom reported.Herein,the interrelations of Se-alloying induced changes in structural phase transition,band structure and TE properties of p-type zone-melted Sb_(2)Te_(3-x)Se_(x)(x=1.5-2.4)alloys near phase transition boundary are systematically investigated.The results demonstrate that Sb_(2)Te_(3-x)Se_(x) shows a structural transition from a rhombohedral phase to mixed structure at x=2.0.The carrier concentration and bandgap at room temperature of Sb_(2)Te_(3)-xSex(x=1.5-2.4)constantly decrease with increasing Se contents x.The zT peak of the Sb_(2)TeSe_(2) matrix is improved and shifted to higher temperature by optimizing carrier concentration via Ag doping.A maximum zT of~0.4 is obtained at 680 K in Sb_(1.97)Ag_(0.03)TeSe_(2) alloy,about 100% enhancement compared with the undoped sample.