同构合金化对P型ZrCoSb基高熵half-Heusler合金热电性能的影响

Effects of Isomorphic Alloying on the Thermoelectric Properties of a P-type ZrCoSb-based High-entropy Half-Heusler Alloy

Half-Heusler(HH)合金由于其本身具有较为优异的力学性能和高温热稳定性,已成为目前最具有应用前景的中高温热电材料之一。然而,其本身较高的本征晶格热导率阻碍了热电性能的进一步提升。本文以P型Zr Co Sb0.85Sn0.15合金为研究对象,基于同构合金化具有优异P型热电性能的(Nb0.8Ta0.2)0.8Ti0.2Fe Sb,通过磁悬浮熔炼和放电等离子烧结设计并制备出一种(Zr Co Sb0.85Sn0.15)1-x[(Nb0.8Ta0.2)0.8Ti0.2Fe Sb]x(x=0,0.2,0.3,0.4,0.5)高熵HH合金。微观组织分析表明,同构合金化这一策略引入了大量多尺度多衬度的第二相,这将有效增强对声子的散射。其中,当同构合金化含量为0.3时,晶格热导率在923 K时从Zr Co Sb0.85Sn0.15的4.72 W·m-1·K-1降至3.07 W·m-1·K-1,降低了35%。然而,由于多位点合金化元素间存在较为复杂的掺杂效果,使其电导率和塞贝克系数同时降低,最终导致热电优值存在一定的降低。本研究工作表明,高熵合金设计思想是一种降低HH热电合金晶格热导率的有力措施。

Due to its excellent mechanical properties and high-temperature thermal stability,half-Heusler(HH)alloy has become one of the most promising medium-and high-temperature thermoelectric materials.However,its high intrinsic lattice thermal conductivity prevents further improvement of its thermoelectric properties.In this paper,the P-type ZrCoSb0.85Sn0.15 alloy is taken as the research object.Based on the isomorphic alloying of(Nb0.8Ta0.2)0.8Ti0.2FeSb with excellent P-type thermoelectric properties,high-entropy HH alloys(ZrCoSb0.85Sn0.15)1-x[(Nb0.8Ta0.2)0.8Ti0.2FeSb]x(x=0,0.2,0.3,0.4,0.5)were designed and prepared by magnetic levitation melting and spark plasma sintering.Microstructure analysis reveals that the isomorphic alloying strategy introduces many multi-scale and multi-contrast second phases,which effectively enhance the scattering of phonons.When the isomorphic alloying content is 0.3,the lattice thermal conductivity decreases by 35%from 4.72 W·m-1·K-1 for ZrCoSb0.85Sn0.15 to 3.07 W·m-1·K-1 at 923 K.However,due to the complex doping effect between the multi-site alloyed elements,the electrical conductivity and Seebeck coefficient decrease simultaneously,resulting in a certain decrease in the thermoelectric figure of merit.This work shows that the high-entropy alloy design approach is a powerful measure for reducing the lattice thermal conductivity of HH thermoelectric alloys.