title: Broad temperature plateau for thermoelectric figure of merit ZT>2 in phase-separated PbTe0.7S0.3.
abstract: Thermoelectrics interconvert heat to electricity and are of great interest in waste heat recovery, solid-state cooling and so on. The efficiency of thermoelectric materials depends directly on the average ZT (dimensionless figure of merit) over a certain temperature range, which historically has been challenging to increase. Here we report that 2.5% K-doped PbTe0.7S0.3 achieves a ZT of >2 for a very wide temperature range from 673 to 923 K and has a record high average ZT of 1.56 (corresponding to a theoretical energy conversion efficiency of ~20.7% at the temperature gradient from 300 to 900 K). The PbTe0.7S0.3 composition shows spinodal decomposition with large PbTe-rich and PbS-rich regions where each region exhibits dissimilar types of nanostructures. Such high average ZT is obtained by synergistically optimized electrical- and thermal-transport properties via carrier concentration tuning, band structure engineering and hierarchical architecturing, and highlights a realistic prospect of wide applications of thermoelectrics.
authors: 1] Department of Physics, South University of Science and Technology of China, Shenzhen 518055, China [2].
authors: H J
authors: HJ
authors: Wu
authors: 1] Department of Chemistry, Northwestern University, Evanston, Illinois 60208, USA [2].
authors: L-D
authors: LD
authors: Zhao
authors: Department of Physics, South University of Science and Technology of China, Shenzhen 518055, China.
authors: F S
authors: FS
authors: Zheng
authors: Department of Physics, South University of Science and Technology of China, Shenzhen 518055, China.
authors: D
authors: D
authors: Wu
authors: School of Materials Science and Engineering, Beihang University, Beijing 100191, China.
authors: Y L
authors: YL
authors: Pei
authors: Department of Physics, South University of Science and Technology of China, Shenzhen 518055, China.
authors: X
authors: X
authors: Tong
authors: Department of Chemistry, Northwestern University, Evanston, Illinois 60208, USA.
authors: M G
authors: MG
authors: Kanatzidis
authors: Department of Physics, South University of Science and Technology of China, Shenzhen 518055, China.
authors: J Q
authors: JQ
authors: He