不同元素替代掺杂化合物M_(0.04)Ti_(0.96)S_2(M=Ni,Al,Mg)的热电性质(英文)

Thermoelectric Properties of Doped Compounds M_(0.04)Ti_(0.96)S_2(M=Ni,Al,Mg)

层状结构TiS2具有准二维结构,高热电势(室温时S≈250μV/K)和大的热电功率因子,作为热电材料具有很好的开发和应用前景。通过固相反应法,我们分别用原子量大于和小于Ti的原子部分替代Ti位引入替位缺陷(NiTi″,AlTi′,MgTi″),合成了不同元素替代掺杂化合物M0.04Ti0.96S2(M=Ni,Al,Mg),在5-310K的温度范围内研究了各化合物的电阻率、热导率及热电势率与温度的对应关系。结果表明Ni、Al、Mg三种元素的掺杂均引起了主体材料从金属性到半导体导电性质的转变,且在低温范围内呈现莫特二维变程跳跃电导规律,lnσ∝T-1/3,表明了TiS2的二维导电机制。值得注意的是:①Mg、Al的掺杂引起了热电势绝对值的显著增高,特别是Al掺杂的化合物在310K时热电势率为-500μV/K,达到了纯TiS2的200%;②Ni掺杂也在整个研究温区引起热导率的明显下降,而Mg、Al的掺杂却在整个研究温区引起热导率的明显升高。由于电阻率的增大,Ni、Al的掺杂均没能使得材料的ZT值有所提高,而Mg的掺杂明显地提高了TiS2的ZT值,在310K其ZT值是纯TiS2的1.6倍。这表明元素掺杂是提高材料的热电优值的有效途径之一。

Element doped compounds M 0.04 Ti 0.96 S2（M=Ni,Al,Mg）were prepared by solid-state reaction,and their transport and thermoelectric properties were investigated from 5K to 310K.The results indicated that electric resistivity ρ increased as M（=Ni,Al,Mg）was introduced,at low temperatures ρ-T curves for M 0.04 Ti 0.96 S2（M=Ni,Al,Mg）were found to obey the Mott＇s two-dimensional hopping law ln ρ-T-1/3,indicating that TiS2 possess 2D transport characteristics.The appearance of Mott＇s 2D law could originate from potential disorder introduced by M substitution for Ti in S-Ti-S slabs.Moreover,it was found that the absolute thermopower ｜S｜ for Al,Mg doped compounds increased significantly in the whole temperature range investigated,and specifically the ｜S｜ of Al 0.04 Ti 0.96 S2 is about 500μV/K,it is -2 times as great as that of TiS2 at 310K.ZT of the Mg doped compound Mg 0.04 Ti 0.96 S2 is -1.6 times as great as that of TiS2 at 310K,indicating that element doping is an effective approach to enhance thermoelectric performance of TiS2.