Thermoelectric Properties and Investigations of Low Thermal Conductivity in Ga-doped Cu2GeSe3
Thermoelectric Properties and Investigations of Low Thermal Conductivity in Ga-doped Cu2GeSe3
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DOI：
10.1103/physrevb.84.085207
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发表时间：
2011-08
影响因子：
3.7
通讯作者：
J. Cho;Xun Shi;J. Salvador;G. Meisner;Jihui Yang;Hsin Wang;A. Wereszczak;Xiaoyuan Zhou;C. U
中科院分区：
文献类型：
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作者：
J. Cho;Xun Shi;J. Salvador;G. Meisner;Jihui Yang;Hsin Wang;A. Wereszczak;Xiaoyuan Zhou;C. U
在这项研究中，我们合成了一系列低热导率的类金刚石材料，其通式为CuGaGeSe 0 ≤≤ 0.1，并评估了它们的输运性质，以确定它们是否适用于基于热电的废热回收应用。我们报告了CuGaGeSefor= 0.01，0.03，0.05，0.07和0.1的Seebeck系数（），电阻率（ρ），热导率（κ），霍尔系数（），晶体结构和弹性性质的结果。粉末X射线衍射显示，少量的相关立方多晶型物出现，沿着与正交晶母相，在高Ga浓度。这种立方相与母相相关，因为两者都含有三维四面体金刚石状子结构。所有的样品都显示出正值和在整个温度范围内研究，指示型电荷载流子。对于未掺杂的CuGeSe，在745 K时观察到= 446 μV K的最大值。随着Ga含量的增加，ρ和σ均减小。所有样品的κ值都很低，未掺杂的CuGeSe在745 K时κ值最低，为0.67 W mK。该值接近这些材料在高温下的理论最小热导率。一个异常大的Grüneisen参数（γ），一个键的非谐性的措施，观察到的CuGaGeSe，即使这种钻石状材料具有高度对称，较低的配位数四面体键。根据弹性性能、热容和体积热膨胀的测量值计算γ= 1.7的值。考虑到所研究的所有材料都具有相似的弹性性能值和可能相当的热膨胀系数，我们推测这种大的Grüneisen参数是这种材料系统的一般特征。我们的结论是，这种高水平的非谐性引起增强的声子-声子散射，除了由无序结构所带来的散射，导致非常低的热导率值。
In this study, we synthesized a series of low thermal conductivity diamondlike materials with the general formula CuGaGeSefor 0 ≤≤ 0.1, and their transport properties were evaluated to establish their suitability for thermoelectric-based waste heat recovery applications. We report results for the Seebeck coefficient (), electrical resistivity (ρ), thermal conductivity (κ), Hall coefficient (), crystal structure, and elastic properties of CuGaGeSefor= 0.01, 0.03, 0.05, 0.07 and 0.1. Powder x-ray diffraction revealed that a small amount of a related cubic polymorph appeared, along with the orthorhombic parent phase, at high Ga concentrations. This cubic phase is related to the parent phase in that both contain three-dimensional tetrahedral diamondlike substructures. All samples showed positive values ofandover the entire temperature range studied, indicative of-type charge carriers. The largest value of= 446 μV Kwas observed at 745 K for undoped CuGeSe. With increasing Ga content, bothandρdecreased. Low values ofκwere observed for all samples, with the lowest value ofκ= 0.67 W mKat 745 K for undoped CuGeSe. This value approaches the theoretical minimum thermal conductivity for these materials at high temperatures. An unusually large Grüneisen parameter (γ), a measure of bonding anharmonicity, was observed for CuGaGeSeeven though this diamondlike material has highly symmetric, lower coordination number tetrahedral bonding. A value ofγ= 1.7 was calculated from the measured values of the elastic properties, heat capacity, and volume thermal expansion. Given that all materials investigated have similar elastic property values and likely comparable coefficients of thermal expansion, we surmise that this large Grüneisen parameter is a general feature for this material system. We conclude that this high level of anharmonicity gives rise to enhanced phonon–phonon scattering, in addition to the scattering brought about by the disordered structure, resulting in very low values of thermal conductivity.