【摘 要】
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Lead-free SnTe compound shows promising good thermoelectric performance.However,stoichiometric SnTe is a strongly p-type semiconductor with a carrier concentration of about 1×1020 cm-3,which correspon
【机 构】
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Key Laboratory of Cryogenics,Technical Institute of Physics and Chemistry,Chinese Academy of Science
【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
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Lead-free SnTe compound shows promising good thermoelectric performance.However,stoichiometric SnTe is a strongly p-type semiconductor with a carrier concentration of about 1×1020 cm-3,which corresponds to a minimum Seebeck coefficient and zT.While in the case of p-PbTe(and n-type La3Te4)one would normally achieve higher zT by doping into the deeper band with higher valley degeneracy,SnTe behaves differently.It is the lighter,upper valence band is shown in this work to result in a higher zT.Therefore decreasing the hole concentration to maximize performance of the light band results in higher zT than doping into the high degeneracy heavy band.Here we tune the electrical transport properties of SnTe by decreasing carrier concentration with Iodine doping,and increasing the carrier concentration with Gd or Te doping.A peak zT value of 0.6 at 700 K was obtained for SnTe0.985I0.015 which optimizes the light,upper valence band,which is about 50%higher than the other peak zT value of 0.4 for GdzSn1-zTe and SnTe1+y which optimize the high valley degeneracy lower valence band.Some group Ⅲ elements such as indium are known to produce the resonant impurity states in Ⅳ-Ⅵcompounds.The discovery of these impurity states has opened up new ways for controlling the thermoelectric properties of Ⅳ-Ⅵ compounds.We carried out a detailed investigation of In as a resonant dopant in SnTe by co-doping with both indium and either Ag or I(extrinsic donors or acceptors)over a temperature range of 300-873K.A stabilization region was observed for co-doped SnTe with In and Ag acceptors(or I donors)in a small region,which we attribute to pinning of the Fermi level(electron chemical potential).With increasing dopant concentration(Iodine or silver),the Hall carrier concentration was proportional to supplementary impurity content.This means that only when the indium resonant states were saturated,the Fermi level could change linearly with additional dopant addition(doping region).Peak zT values(0.8 at 873K)were obtained on the boundary of stabilization region and doping region.
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