On the role of Mg content in Mg2(Si,Sn): Assessing its impact on electronic transport and estimating the phase width by in situ characterization and modelling
On the role of Mg content in Mg2(Si,Sn): Assessing its impact on electronic transport and estimating the phase width by in situ characterization and modelling
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DOI：
10.1016/j.mtphys.2021.100471
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发表时间：
2021-07
影响因子：
11.5
通讯作者：
Aryan Sankhla;H. Kamila;H. Naithani;E. Mueller;J. Boor
中科院分区：
文献类型：
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作者：
Aryan Sankhla;H. Kamila;H. Naithani;E. Mueller;J. Boor
实验发现Mg 2Si 1-xSnx热电材料中载流子输运对高温热处理非常敏感，特别是精确的Mg含量的作用一直存在争议。考虑到这一点，原位测量了Sb掺杂Mg2Si0.4Sn0.6在710 K退火过程中的电输运性质。我们测量了两个准相同的样品：样品1，用于在氦气中测量塞贝克系数和电导率（σ），样品2用于在真空中测量霍尔系数和σ。两种样品在很大程度上保持单相，并且在分别退火10276小时和101100小时后没有显示出分层。所观察到的实验数据可以建模使用一个单一的和两个抛物线带模型和一个连续减少多数载流子被确定，这可以链接到镁损失。深入的分析还揭示了迁移率损失和降低的状态密度的有效质量，这可能是由于正在进行的镁损失或由于在室温下的Mg 2 Si 0.4 Sn 0.6的导带的简并性提高。最后，我们可以将载流子浓度的变化与Mg相关缺陷的变化联系起来，并确定Mg 2-δ Si 0.4 Sn 0.6中的相宽度Δ δ。
Abstract Carrier transport in Mg 2 Si 1-x Sn x thermoelectrics was experimentally found to be highly sensitive to high temperature heat treatment and in particular the role of the precise Mg content has been discussed controversially. Considering this, electrical transport properties of Sb doped Mg 2 Si 0.4 Sn 0.6 were measured in-situ during annealing at 710 K. We measured two quasi-identical samples: sample 1, for the Seebeck coefficient and the electrical conductivity (σ) measurement in helium, and sample 2 for Hall coefficient and σ measurement in vacuum, respectively. Both samples largely remain single phase and did not show de-mixing after annealing for∼ 276 hours and∼ 1100 hours respectively. The observed experimental data can be modelled using a single-and two parabolic band model and a continuous reduction in majority carriers is identified, which can be linked to Mg loss. Thorough analysis furthermore reveals mobility loss and a lowering of the density of states effective mass which could both be due to ongoing Mg loss or due to a lifted degeneracy of conduction bands in Mg 2 Si 0.4 Sn 0.6 at room temperature. Finally, we can link the change in carrier concentration to a change in Mg-related defects and identify a phase width Δ δ in Mg 2-δ Si 0.4 Sn 0.6.