以Mg、Si、Sn、Sb块体为原料, 采用熔炼结合放电等离子烧结(SPS)技术制备了n型(Mg2Si1-xSbx)0.4-(Mg2Sn)0.6(0≤x≤0.0625)系列固溶体合金. 结构及热电输运特性分析结果表明: 当Mg原料过量8wt%时, 可以弥补熔炼过程中Mg的挥发损失, 形成单相(Mg2Si1-xSbx)0.4-(Mg2Sn)0.6固溶体. 烧结样品的晶胞随Sb掺杂量的增加而增大; 电阻率随Sb掺杂量的增加先减小后增大, 当样品中Sb掺杂量x≤0.025时, 样品电阻率呈现出半导体输运特性, Sb掺杂量x>0.025时, 样品电阻率呈现为金属输运特性. Seebeck系数的绝对值随Sb掺杂量的增加先减小后增大; 热导率κ在Sb掺杂量x≤0.025时比未掺杂Sb样品的热导率低, 在Sb掺杂量x>0.025时高于未掺杂样品的热导率, 但所有样品的晶格热导率明显低于未掺杂样品的晶格热导率. 实验结果表明Sb的掺杂有利于降低晶格热导率和电阻率, 提高中温区Seebeck系数绝对值; 其中(Mg2Si0.95Sb0.05)0.4-(Mg2Sn)0.6合金具有最大ZT值, 并在723 K附近取得最大值约为1.22.
n-type (Mg2Si1-xSbx)0.4-(Mg2Sn)0.6 (0≤x≤0.0625) alloys were prepared by an induction melting and spark plasma sintering method using bulks of Mn, Si, Sn, Sb as raw materials. The analyzing results of the structure and thermoelectric properties show that the single-phase (Mg2Si1-xSbx)0.4-(Mg2Sn)0.6 alloys can be obtained at 8wt% excess of Mg addition. The lattice constant increases linearly with the amount of Sb, the electrical resistivity ρ firstly increases and then decreases. The electrical resistivity ρ of samples (x≤0.025) shows semi-conductor behavior, while that of the samples (x>0.025) shows the metallic behavior. The Seebeck coefficient a firstly increases and then decreases with the increase of x value. Compared with the non-doped sample, the thermal conductivity k for samples (x≤0.025) decreases and that of the other samples (x>0.025) increases. The ZT value for (Mg2Si0.95Sb0.05)0.4-(Mg2Sn)0.6 sample reaches its highest value of 1.22 at 773 K, which is much higher than that of the non-doped sample.
参考文献
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