Thermoelectric semiconductors based on CoSb_(3)hold the best promise for recovering industrial or automotive waste heat because of their high efficiency and relatively abundant,lead-free constituent elements.However,higher efficiency is needed before thermoelectrics reach economic viability for widespread use.In this study,n-type In_(x)Ce_(y)Co_(4)Sb_(12+z)skutterudites with high thermoelectric performance are produced by combining several phonon scattering mechanisms in a panoscopic synthesis.Using melt spinning followed by spark plasma sintering(MS-SPS),bulk In_(x)Ce_(y)Co_(4)Sb_(12+z)alloys are formed with grain boundaries decorated with nano-phase of InSb.The skutterudite matrix has grains on a scale of 100-200 nm and the InSb nano-phase with a typical size of 5e15 nm is evenly dispersed at the grain boundaries of the skutterudite matrix.Coupled with the presence of defects on the Sb sublattice,this multi-scale nanometer structure is exceptionally effective in scattering phonons and,therefore,InxCey-Co_(4)Sb_(12)/InSb nano-composites have very low lattice thermal conductivity and high zT values reaching in excess of 1.5 at 800 K.
Han LiXianli SuXinfeng TangQingjie ZhangCtirad UherG.Jeffrey SnyderUmut Aydemir
Miniaturization of efficient thermoelectric(TE)devices has long been hindered by the weak mechanical strength and insufficient heat-to-electricity conversion efficiency of zone-melted(ZM)ingots.Here,we successfully prepared a robust high-performance p-type Bi_(0.4)Sb_(1.6)Te_(3.72)bulk alloy by combining an ultrafast thermal explosion reaction with the spark plasma sintering(TER-SPS)process.It is observed that the introduced excess Te not only enhances the(00l)-oriented texture to ensure an outstanding power factor(PF)of 5 mW m^(−1)K^(−2),but also induces extremely high-density line defects of up to 10^(11)–10^(12)cm^(−2).Benefiting from such heavily dense line defects,the enhancement of the electronic thermal conductance from the increased electron mobility is fully compensated by the stronger phonon scattering,leading to an evident net reduction in total thermal conductivity.As a result,a superior ZT value of~1.4 at 350 K is achieved,which is 40%higher than that of commercial ZM ingots.Moreover,owing to the strengthening of grain refinement and highdensity line defects,the mechanical compressive stress reaches up to 94 MPa,which is 154%more than that of commercial single crystals.This research presents an effective strategy for the collaborative optimization of the texture,TE performance,and mechanical strength of Bi2Te3-based materials.As such,the present study contributes significantly to the future commercial development of miniature TE devices.
Pristine GeTe shows inferior thermoelectric performance around unit due to the large carrier concentration induced by the presence of intrinsic high concentration of Ge vacancy. In this study, we report a thermoelectric figure of merit ZT of 1.56 at 700 K, realized in Sb-doped GeTe based thermoelectric(TE)materials via combined effect of suppression of intrinsic Ge vacancy and Sb doping. The nonequilibrium nature during melt spinning process plays very important role. For one thing, it promotes the homogeneity in Ge_(1-x)Sb_xTe samples and refines the grain size of the product. Moreover the persistent Ge precipitated as impurity phase in the traditional synthesis process is found to be dissolved back into the GeTe sublattice, accompanying with a drastic suppression of Ge vacancies concentration which in combination with Sb electron doping significantly reduced the inherent carrier concentration in GeTe.Low carrier concentration, approaching the optimum carrier concentration ～3.74 × 10^(-20) cm^(-3) and a high power factor of 4.01 × 10^(-3) W m^(-1)K^(-2) at 750 K are achieved for Ge_(0.98)Sb_(0.02) Te sample. In addition,the enhanced grain boundary phonon scattering by refining the grain size through melt spinning(MS)process, coupled with the intensified alloying phonon scattering via Sb doping leads to low thermal conductivity of 1.53 W m^(-1) K^(-1) at 700 K for Ge_(0.94) Sb_(0.06) Te sample. All those contribute to a high ZT value,representing over 50% improvement in the ZT value compared to the Sb free samples, which provides an alternative way for ultrafast synthesis of high performance GeTe based thermoelectric material.
