【摘 要】
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Lead chalcogenides are dominant thermoelectric materials in the medium-temperature range,owing to their highly favorable electronic band structures and low thermal conductivities achievable.An importa
【机 构】
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Department of Physics,South University of Science and Technology of China,Shenzhen,518055,China
【出 处】
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第六届海内外中华青年材料科学技术研讨会暨第十五届全国青年材料科学技术研讨会
论文部分内容阅读
Lead chalcogenides are dominant thermoelectric materials in the medium-temperature range,owing to their highly favorable electronic band structures and low thermal conductivities achievable.An important system is the PbTe-PbS pseudo-binary and its low thermal conductivity originates largely from the coexistence of both alloying and nanostructuring through phase-separation.To better understand the competition between alloying and phase separation,and its pronounced effects on the thermoelectric performance in PbTe-PbS,we systematically studied,via transmission electron microscopy(TEM)observations and theoretical calculations,K-and Na-doped(PbTe)1-x(PbS)x pseudo-binaries.In both systems,we have achieved broad plateau of figure of merit ZT,with the highest values of 2.2[1] and 2.3 [2]at 923 K,individually.In K-doped system,the high-density nano-precipiates in both PbTe and PbS grains,together with the PbTe-PbS phase boundaries,provide very strong scattering effect on phonons,leading to a record low thermal conductivity ever reported in lead chalcogenides.In Na-doped system,the lowest lattice thermal conductivity of the series was achieved when the PbS phase-fraction,x,was 20%,originating from the all-scale hierarchical structures and SPS processes;we also studied the onset of carrier concentration modulation~600 K,which leads to the observed saturation of electrical transport properties due to the diffusion and re-dissolution of excessive Na into the PbTe-PbS matrix.This carrier concentration modulation,is equally crucial to achieve the very high power factors(up to 26.5 μW/cmK2 at 623 K)and the outstanding thermoelectric performances in SPSed PbTe-PbS binaries.
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