Transport and thermoelectric properties of nanocrystal substitutional
Transport and thermoelectric properties of nanocrystal substitutional
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DOI：
10.1016/j.jallcom.2009.04.130
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发表时间：
2009-09
期刊：
影响因子：
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通讯作者：
Kunpu Zhang;Xuming Qin;H. Xin;Huiyuan Li;J. J. Zhang-J.-
中科院分区：
文献类型：
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作者：
Kunpu Zhang;Xuming Qin;H. Xin;Huiyuan Li;J. J. Zhang-J.-
采用机械合金化结合热压的方法制备了（Mg 1-xCdx）3Sb 2（x=0-0.3）和3Sb 2（Mg0.7Cd0.25Ag0.05）纳米晶，平均晶粒尺寸约为35 nm，研究了它们在310 ~ 20 K温度范围内的输运和热电性能.结果表明，（Mg 1 −xCdx）3Sb 2的电阻率随Cd含量x的增加而降低，这可能是由于掺杂后晶格畸变间接导致载流子浓度增加所致.（Mg0.7Cd0.25Ag0.05）3Sb 2的电阻率比（Mg 1-xCdx）3Sb 2的电阻率大得多的降低应该源于由于引入受主杂质Ag而导致的空穴浓度的显著增加。在较低的温度范围内，观察到莫特的T-1/4定律，这可以归因于掺杂时晶格畸变引起的严重的潜在无序。所有取代和共掺杂样品的塞贝克系数下降，大概是由于载流子浓度增加。此外，（Mg 1-xCdx）3Sb 2的热导率随着x的增加而单调下降，这是由于原子量较大的杂质（Cd）的声子散射。轻微沉淀的元素Sb和Cd相的存在应该是观察到的3Sb 2样品的较大热导率的原因。Mg0.7Cd0.25Ag0.05所有掺杂样品的ZT值都有所提高。特别是（Mg0.7Cd0.25Ag0.05）3Sb 2的ZT在300 K时达到0.01，比未掺杂的和仅少量掺杂Cd的样品提高了几个数量级。研究结果表明，适量的Cd替代和Ag共掺杂可以有效地改善Mg3 Sb 2体系的热电性能。
Nanocrystalline (Mg1−xCdx)3Sb2(x=0–0.3) and nominally (Mg0.7Cd0.25Ag0.05)3Sb2with a mean grain size of ∼35nm were prepared by mechanical alloying plus hot-pressing, and their transport and thermoelectric properties were investigated from 310K down to 20K. The results indicated that electric resistivity of (Mg1−xCdx)3Sb2decreased with increasing Cd content x, which could be ascribed to increase in carrier concentration indirectly caused by lattice distortion after substituted. The much larger decrease in the resistivity of (Mg0.7Cd0.25Ag0.05)3Sb2than that of (Mg1−xCdx)3Sb2should originate from substantial increase in hole concentration due to introduction of acceptor impurity Ag. At lower temperature regimes, Mott's T−1/4law was observed, which could be attributed to the severe potential disorder caused by lattice distortion upon doping. Seebeck coefficient of all the substituted and co-doped specimens decreased presumably due to increased carrier concentration. Moreover, thermal conductivity of (Mg1−xCdx)3Sb2decreased monotonously with increasing x due to phonon scattering of the impurity (Cd) with greater atomic weight. The presence of slight precipitated elementary Sb and Cd phases should be responsible for the observed larger thermal conductivity of (Mg0.7Cd0.25Ag0.05)3Sb2specimen. The values of the ZT for all the doped specimens enhanced. Especially, ZT of (Mg0.7Cd0.25Ag0.05)3Sb2reach 0.01 at 300K, which is several orders magnitude higher than that un-doped one and those doped slightly with Cd only. Present result indicates that thermoelectric properties of Mg3Sb2system can be effectively improved by the proper substitution of element Cd and co-doped with element Ag.