The electrical and thermal conductivity and thermopower of nickel doped compounds (NixTi1−x)1+yS2 at low temperatures
The electrical and thermal conductivity and thermopower of nickel doped compounds (NixTi1−x)1+yS2 at low temperatures
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DOI：
10.1088/0022-3727/39/6/033
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发表时间：
2006-03
期刊：
影响因子：
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通讯作者：
Junya Zhang;X. Qin;Di Li;H. Dong
中科院分区：
文献类型：
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作者：
Junya Zhang;X. Qin;Di Li;H. Dong
采用固相反应法制备了掺镍化合物（NixTi 1 −x）1+ yS 2（0 <$x <$0. 06），研究了其在5 ~ 310 K温度范围内的直流电导率、热导率和热电势。结果表明，Ni掺杂引起了类金属到类超导体的行为转变;在低温下（T0）服从Mott的二维变程跳跃定律ln σ <$T−1/3，表明TiS 2具有二维输运特性。Mott二维定律的出现可能是由于Ni替代S-Ti-S中Ti引入的势无序，而金属-半导体转变则是由于Ni替代导致电子浓度降低而引起的去简并。实验还表明，掺杂后化合物的晶格热导率和载流子（主要是电子）热导率均降低，这可以分别解释为Ni的嵌入取代和掺杂后载流子浓度降低的综合效应。绝对塞贝克系数|S|发现掺杂后的降低，这可能是由于Ni取代Ti后产生了一些空穴。与TiS 2相比，掺杂化合物（NixTi 1-x）1+ yS 2（x > 0）的品质因数ZT降低，这是由于它们的电阻率大幅增加和它们的塞贝克系数明显降低。
Nickel doped compounds (NixTi1−x)1+yS2 (0 ⩽ x ⩽ 0.06) were prepared by solid-state reaction, and their dc electrical and thermal conductivity and thermopower were investigated from 5 K to 310 K. The results indicated that Ni doping caused a metal-like to semiconductor-like behaviour transition; at low temperatures (T 0) obeys Mott's 2D variable range hopping law, ln σ ∝ T−1/3, indicating that TiS2 possesses 2D transport characteristics. The appearance of Mott's 2D law could originate from potential disorder introduced by Ni substitution for Ti in S–Ti–S slabs, while the metal-to-semiconductor transition can be ascribed to de-degeneration through reduction in electron concentration due to Ni substitution. Experiments also indicated that both lattice thermal conductivity and carrier (mainly electron) thermal conductivity of the doped compounds decreased upon doping, which can be explained as the combined effects of substitution with intercalation of Ni and reduction of carrier concentration upon doping, respectively. The absolute Seebeck coefficient |S| was found to decrease after doping, which could be attributed to generation of some holes after Ni substitution for Ti. The figure of merit, ZT, of the doped compounds (NixTi1−x)1+yS2 (x > 0) decreased as compared with TiS2 due to both a large increase in their resistivity and an obvious decrease in their Seebeck coefficient.