Localized vibrational modes in metallic solids
Localized vibrational modes in metallic solids
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DOI：
10.1038/27625
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发表时间：
1998-10-29
期刊：
影响因子：
64.8
通讯作者：
Bennington, S
中科院分区：
文献类型：
--
作者：
Keppens, V;Mandrus, D;Bennington, S
填充方钴矿锑化物（1，2）是具有式RM 4Sb 12的立方化合物，其中R是稀土元素（例如La或Ce），并且M是过渡金属（例如Fe或Co）。稀土离子被弱束缚在由其他原子形成的超大原子笼中。它的存在已被证明会导致热导率的晶格分量的显著降低，而对化合物的电子性质（3-5）几乎没有影响。这种性质的组合使得填充的方钴矿作为热电材料受到关注。有人提出（4），稀土离子的局部非相干振动是热导率降低的原因，但没有直接证据表明存在这些局部振动模式。在这里，我们报告的本地模式在La填充方钴矿的观察，使用热容，弹性常数和非弹性中子散射测量。La原子表现出不寻常的热力学行为，其特征在于存在两个低能量局域模式。我们的研究结果表明，考虑本地模式将发挥重要作用，在下一代热电材料的设计。
Filled skutterudite antimonides(1,2) are cubic compounds with the formula RM4Sb12, where R is a rare-earth element (such as La or Ce), and M is a transition metal (for example, Fe or Co). The rare-earth ion is weakly bound in an oversized atomic cage formed by the other atoms. Its presence has been shown to cause a dramatic reduction in the lattice component of the thermal conductivity, while having little effect on the electronic properties(3-5) of the compound. This combination of properties makes filled skutterudites of interest as thermoelectric materials. It has been suggested(4) that localized, incoherent vibrations of the rare-earth ion are responsible for the reduction in thermal conductivity, but no direct evidence for these local vibrational modes exists. Here we report the observation of local modes in La-filled skutterudites, using heat capacity, elastic constant and inelastic neutron scattering measurements. The La atoms show unusual thermodynamic behaviour, characterized by the presence of two low-energy localized modes. Our results suggest that consideration of local modes will play an important role in the design of the next generation of thermoelectric materials.