High Thermoelectric Performance of In4Se3-Based Materials and the Influencing Factors.
High Thermoelectric Performance of In4Se3-Based Materials and the Influencing Factors.
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DOI：
10.1021/acs.accounts.7b00480
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发表时间：
2018-01
影响因子：
18.3
通讯作者：
Xin Yin;Jingyan Liu;Ling Chen;Li‐Ming Wu
中科院分区：
文献类型：
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作者：
Xin Yin;Jingyan Liu;Ling Chen;Li‐Ming Wu
可以直接将电转化为热的材料，即，热电材料在可持续能源应用方面再次吸引了全球的关注。作为最先进的热电材料之一，In 4Se 3具有一种有趣的准二维片的晶体结构，包括In/Se链，其提供了实现Peierls畸变的平台并支持电荷密度波不稳定性。单晶In_4Se_（3-δ）（δ = 0.65）在其热电性能中显示出强的各向异性，在b-c平面中具有非常高的ZT，在705 K时为1.48（迄今为止n型热电材料的最高值之一），但在a-b平面中具有低得多的ZT，约为0.5。由于晶粒的随机弥散和晶界效应，多晶In 4Se 3的电输运性能较差，是影响其性能提高的主要障碍。In 4Se 3晶胞中的In 4位取代了诸如Pb的掺杂剂，这将载流子浓度提高了2个数量级，电导率提高到143 S/cm。此外，当Cu掺杂到间隙位置中时，电导率显著增加到约160 S/cm，但使用In 1/In 2/In 3位置掺杂剂（例如，Ni、Zn、Ga和Sn。特别地，In 4位掺杂剂镱引入了高度局部化电荷载流子的钉扎水平;因此，电导率保持在30 S/cm的数量级内。同时，镱还在费米能级附近产生共振态，使塞贝克系数增加到-350 μV/K，这是ZT峰处的最高值。然而，掺杂剂的最大溶解度可能受到Se空位浓度的限制。此外，Se空位还破坏了晶格的规则振动，削弱了声子输运。最后，纳米夹杂物可以有效地散射中间波长的声子，导致晶格热导率的降低。由于多掺杂策略，多晶材料在ZT值方面与单晶具有竞争力;例如，Pb/Sn共掺杂的In4Pb0.01Sn0.04Se3在733 K时的ZT = 1.4，而In4Se2.95（CuI）0.01在723 K时的ZT = 1.34。这些特性说明了多晶In 4Se 3基材料在各种应用中的前景。最后，所有单晶和多晶In 4Se 3材料的ZT值已被总结为在不同的晶格位置处应用的掺杂策略的函数。此外，所有的多晶材料的电导率和塞贝克系数之间的相关性。这些见解可能会提供新的思路，在寻找和选择新的热电化合物在In/Se和相关的In/Te，Sn/Se，和Sn/Te系统。
Materials that can directly convert electricity into heat, i.e., thermoelectric materials, have attracted renewed attention globally for sustainable energy applications. As one of the state-of-the-art thermoelectric materials, In4Se3 features an interesting crystal structure of quasi-two-dimensional sheets comprising In/Se chains that provide a platform to achieve a Peierls distortion and support a charge density wave instability. Single-crystal In4Se3-δ (δ = 0.65) shows strong anisotropy in its thermoelectric properties with a very high ZT of 1.48 at 705 K in the b-c plane (one of the highest values for an n-type thermoelectric material to date) but a much lower ZT of approximately 0.5 in the a-b plane. Because of the random dispersion of grains and the grain boundary effect, the electrical transport properties of polycrystalline In4Se3 are poor, which is the main impediment to improve their performance. The In4-site in the In4Se3 unit cell is substitutional for dopants such as Pb, which increases the carrier concentration by 2 orders of magnitude and the electrical conductivity to 143 S/cm. Furthermore, the electrical conductivity markedly increases to approximately 160 S/cm when Cu is doped into the interstitial site but remains as low as 30 S/cm with In1/In2/In3-site dopants, e.g., Ni, Zn, Ga, and Sn. In particular, the In4-site dopant ytterbium introduces a pinning level that highly localizes the charge carriers; thus, the electrical conductivity is maintained within an order of magnitude of 30 S/cm. Meanwhile, ytterbium also creates resonance states around the Fermi level that increase the Seebeck coefficient to -350 μV/K, the highest value at the ZT peak. However, the maximum solubility of the dopant may be limited by the Se-vacancy concentration. In addition, a Se vacancy also destroys the regular lattice vibrations and weakens phonon transport. Finally, nanoinclusions can effectively scatter the middle wavelength phonons, resulting in a decrease in the lattice thermal conductivity. Because of the multiple-dopant strategy, polycrystalline materials are competitive with single crystals regarding ZT values; for instance, Pb/Sn-co-doped In4Pb0.01Sn0.04Se3 has ZT = 1.4 at 733 K, whereas In4Se2.95(CuI)0.01 has ZT = 1.34 at 723 K. These properties illustrate the promise of polycrystalline In4Se3-based materials for various applications. Finally, the ZT values of all single crystalline and polycrystalline In4Se3 materials have been summarized as a function of the doping strategy applied at the different lattice sites. Additionally, the correlations between the electrical conductivity and the Seebeck coefficient of all the polycrystalline materials are presented. These insights may provide new ideas in the search for and selection of new thermoelectric compounds in the In/Se and related In/Te, Sn/Se, and Sn/Te systems.