Cha Joonil, Zhou Chongjian, Cho Sung-Pyo, Park Sang Hyun, Chung In
Center for Nanoparticle Research , Institute for Basic Science (IBS) , Seoul 08826 , Republic of Korea.
Korea Institute of Energy Research , Daejeon 34129 , Republic of Korea.
ACS Appl Mater Interfaces. 2019 Aug 28;11(34):30999-31008. doi: 10.1021/acsami.9b10394. Epub 2019 Aug 16.
The thermoelectric (TE) community has mainly focused on improving the figure of merit (ZT) of materials. However, the output power of TE devices directly depends on the power factor (PF) rather than ZT. Effective strategies of enhancing PF have been elusive for BiTe-based compounds, which are efficient thermoelectrics operating near ambient temperature. Here, we report ultrahigh carrier mobility of ∼467 cm V s and power factor of ∼45 μW cm K in a new n-type BiTe system with nominal composition CuBiTe ( = 0.02, 0.04, and 0.06). It is obtained by reacting BiTe with surplus Cu and Te and subsequently pressing powder products by spark plasma sintering (SPS). The SPS discharges excess Te but stabilizes the high extent of Cu in the structure, giving unique SPS CuBiTe samples. The analyzed composition is close to "CuBiTe". Their charge transport properties are highly unusual. Hall carrier concentration and mobility simultaneously increase with the higher mole fraction of Cu contrary to the typical carrier scattering mechanism. As a consequence, the electrical conductivity is considerably enhanced with Cu incorporation. The Seebeck coefficient is nearly unchanged by the increasing Cu content in contrast to the general understanding of inverse relationship between electrical conductivity and Seebeck coefficient. These effects synergistically lead to a record high power factor among all polycrystalline n-type BiTe-based materials.
热电（TE）领域主要专注于提高材料的优值（ZT）。然而，TE器件的输出功率直接取决于功率因子（PF）而非ZT。对于基于BiTe的化合物而言，提高PF的有效策略一直难以捉摸，这类化合物是在接近环境温度下运行的高效热电材料。在此，我们报道了一种名义组成为CuBiTe（ = 0.02、0.04和0.06）的新型n型BiTe体系中约467 cm² V⁻¹ s⁻¹的超高载流子迁移率和约45 μW cm⁻¹ K⁻²的功率因子。它是通过使BiTe与过量的Cu和Te反应，随后通过放电等离子烧结（SPS）压制粉末产物而获得的。SPS排出了过量的Te，但使结构中的高含量Cu得以稳定，从而得到独特的SPS CuBiTe样品。分析得到的成分接近“CuBiTe”。它们的电荷传输特性非常独特。与典型的载流子散射机制相反，随着Cu摩尔分数的增加，霍尔载流子浓度和迁移率同时增加。因此，随着Cu的掺入，电导率显著提高。与电导率和塞贝克系数成反比关系的一般理解相反，塞贝克系数几乎不受Cu含量增加的影响。这些效应协同作用，使得在所有多晶n型BiTe基材料中实现了创纪录的高功率因子。
