Synergistically Optimizing Electrical And Thermal Transport Properties Of N-type PbTe

In recent years,the research and development of green new energy materials have received much attention.Thermoelectric materials,as a kind of environmentally-friendly energy material,enable to directly convert thermal energy into electric power,therefore it possesses wide application prospects in waste heat recycling and environmental issue.Among many thermoelectric materials,Pb Te is a kind of thermoelectric material with great application potential in medium-temperature range.At present,high performance p-type Pb Te system has been well developed,but n-type Pb Te still maintains a relatively poor thermoelectric performance.Hence,there is an urgent need to enhance thermoelectric performance of the n-type Pb Te to match its p-type counterpart.In this paper,the high thermoelectric performance of n-type Pb Te is realized by means of synergistically optimizing carrier and phonon transport properties.The main contents of this paper are as follows:(1)The carrier density of Pb Te is optimized by Sb doping,and the maximum value of ZT?1.0 is obtained.Based on the optimized carrier density,introducing ternary compounds Ag Sb Se₂or Ag Sb Te₂suppresses the lattice thermal conductivity,and the minimum lattice thermal conductivity is reduced as low as?0.53 W·m^-1·K^-1and?0.62 W·m^-1·K^-1,respectively.Finally,the maximum ZT values?1.2 and?1.3 are obtained,respectively.(2)In Ag Sb Se₂-alloyed Pb Te samples,the lattice thermal conductivity can be evidently reduced,and the minimum lattice thermal conductivity decreases from?1.1 W·m^-1·K^-1to?0.8W·m^-1·K^-1.Based on Pb Te-5%Ag Sb Se₂matrix,several dopants(Sb,Bi or I)are used to optimize its carrier density,and found that I element is verified to be the most effective dopant to enhance its electrical transport property,which contributes to the maximum power factor?14.8?W·cm^-1·K^-2and the maximum ZT and ZT_avevalues are boosted to?1.0 and?0.77,respectively.(3)Cu-based multi-scale defects are formed by introducing Cu Sb Se₂and additional Cu atoms in the Pb Te matrix,which can synergistically optimize the phonon and carrier transport properties.Alloying Cu Sb Se₂can optimize the power factor,and simultaneously precipitate out embedded Cu-based nanostructures in matrix to lower lattice thermal conductivity.Additionally,adding extra Cu atoms can form interstitials and further improve both the carrier density and carrier mobility.Moreover,the Cu interstitials together with massive Cu-based nanoprecipitates can strongly scatter a wide set of phonons,and further lower the lattice thermal conductivity to?0.44 W·m^-1·K^-1.Finally,these Cu-based hierarchical structures can contribute to a high ZT of?0.5 at 300 K,a peak ZT of?1.4 and a ZT_aveof?0.94.There are 41 figures,2 tables and 86 references in this paper.