Nano‐ and Micro‐Structures Formed during Laser Processing of Selenium Doped Bismuth Telluride
Nano‐ and Micro‐Structures Formed during Laser Processing of Selenium Doped Bismuth Telluride
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DOI：
10.1002/admi.202100185
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发表时间：
2021-07
影响因子：
5.4
通讯作者：
Ryan Welch;D. Hobbis;A. Birnbaum;George Nolas;S. LeBlanc
中科院分区：
文献类型：
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作者：
Ryan Welch;D. Hobbis;A. Birnbaum;George Nolas;S. LeBlanc
热电材料的激光加工提供了一条影响材料纳米和微结构的途径，并实现了促进自由形状器件形状的附加制造工艺，这是热电材料加工所缺乏的能力。本文描述了掺硒碲化铋这一n型热电材料在激光诱导快速熔化和凝固过程中形成的多尺度结构。使用激光粉床熔化(也称为选择性激光熔化)以逐层技术制造宏观样品。激光处理导致高度织构的柱状颗粒沿构建方向取向，纳米尺度的夹杂物，以及主要载流子的移位。稀疏的氧化物夹杂物和碲的偏析使材料转变为p型行为，塞贝克系数在95°C时达到峰值143µV K-1，平均相对密度为74%，制件具有多尺度孔洞和微尺度裂纹，这可能是由于低粉层堆积密度和工艺参数接近导电和小孔模式加工的过渡阈值所致。这些结果提供了关于通过激光熔化诱导纳米结构影响热电材料中载流子传输的途径以及在热电部件中实现有效的粉末固结和分层结构所需的激光加工参数的见解。
Laser processing of thermoelectric materials provides an avenue to influence the nano‐ and micro‐structure of the material and enable additive manufacturing processes that facilitate freeform device shapes, a capability that is lacking in thermoelectric materials processing. This paper describes the multiscale structures formed in selenium‐doped bismuth telluride, an n‐type thermoelectric material, from laser‐induced rapid melting and solidification. Macroscale samples are fabricated in a layer‐by‐layer technique using laser powder bed fusion (also known as selective laser melting). Laser processing results in highly textured columnar grains oriented in the build direction, nanoscale inclusions, and a shift in the primary charge carriers. Sparse oxide inclusions and tellurium segregation shift the material to p‐type behavior with a Seebeck coefficient that peaks at 143 µV K–1 at 95 °C. With an average relative density of 74%, fabricated parts have multiscale porosity and microscale cracking that likely resulted from low powder layer packing density and processing parameters near the transition threshold between conduction and keyhole mode processing. These results provide insights regarding the pathways for influencing carrier transport in thermoelectric materials via laser melting‐induced nanoscale structuring and the laser processing parameters required to achieve effective powder consolidation and hierarchical structuring in thermoelectric parts.