Sn_(1-x)Ge_(x)Te的高温高压合成及热电性能

Synthesis and Thermoelectric Properties of Sn_(1-x)Ge_(x)Te by High Temperature and High Pressure

在众多热电材料中,SnTe具有与PbTe相同的晶体结构且不含重金属Pb,近年来引起了人们的广泛关注。目前,本征SnTe的热电性能并不特别优异,存在以下问题:大量本征Sn空位导致载流子浓度过高,从而降低了电输运性能;价带中的轻带与重带能量劈裂较大,且带隙过窄,不利于通过重带参与电运输提高Seebeck系数;晶格热导率较大。利用高温高压方法快速合成了Ge掺杂的SnTe合金,系统研究了不同Ge含量对SnTe的微观结构和热电性能的影响。结果表明:Ge掺杂能够有效地调控SnTe材料的电运输性能;Ge掺杂使样品的微观结构发生变化,样品晶粒细化,且析出纳米第二相,晶界和纳米相对声子的散射作用降低了热导率;样品Ge_(0.2)Sn_(0.8)Te在700 K时的热电优值达到0.35。

In many thermoelectric materials,SnTe has the same crystal structure as PbTe,but does not contain heavy metal Pb,which has attracted extensive attention in recent years.At present,the thermoelectric properties of intrinsic SnTe are not particularly excellent.There are some disadvantages:a large number of intrinsic Sn vacancies lead to high carrier concentration,which worsens the electrical transport performance;the energy splitting between the light band and the heavy band in the valence band is large and the band gap is too narrow,which is not conducive to the Seebeck coefficient participating in the electrical transport through the heavy band;the lattice thermal conductivity is large.In this study,SnTe doped with Ge was prepared under high pressure and high temperature conditions.The results show that the band structure and the electrical transport properties of SnTe can be tuned effectively by Ge doping.At the same time,Ge doping can modulate the microstructure of the SnTe,which induced the formation of fine grains and second nanophases then reduced the thermal conductivity.The maximum figure-of-merit is 0.35 at 700 K for Ge_(0.2)Sn_(0.8)Te.