微波辅助MgH2固相反应法制备Mg2Si1-xSnx基热电材料及性能研究

Fabrication and thermoelectric performance on Mg2Si1-xSnx prepared from MgH2 by microwave-assisted solid state reaction

摘要:

在微波作用下利用MgH2 、纳米 Si粉 、Sn粉和Bi粉进行固相反应，结合电场激活压力辅助合成法（FAPAS）制备了高纯Bi掺杂的Mg2Si1-xSnx（0.4≦x≦0.6）基固溶体热电材料，并对其微观结构和热电性能进行了表征。研究结果表明，MgH2替代传统原料Mg粉显著降低了固相反应温度且防止了Mg的挥发和氧化，同时微波快速低温加热有效抑制晶粒长大，可获得平均晶粒尺寸为200nm的高纯产物。在300-750K的温度区间对样品热电性能进行测试，结果表明细小的片层固溶体组织和Bi的掺杂有效降低了样品热导率，同时改善了其电性能，在600K时，含1.5at%Bi的Mg2Si0.4Sn0.6热电材料具有最大ZT值0.91。

Abstract:

The synthesis of Bi dopped Mg2Si1-xSnx (0.4≦x≦0.6) solid solution thermoelectric materials with high purity was achieved by microwave-assisted solid state reaction followed by the field activated and pressure assisted synthesis (FAPAS), and its microstructure and transport properties were observed and evaluated. It indicates that the replacement of Mg used in traditional processes by MgH2 powder significantly reduces the temperature of the solid state reaction and further inhibits the oxidation and volatilization of magnesium. Meanwhile, the low-temperature and rapid heating from microwave restrain the grain growth effectively; as a result the pure product with an average grain size of 200nm has been reached. Thermoelectric performance was tested in the temperature range of 300-750K. It indicates that the solid solution with fine lamellar structure and the doping of Bi significantly lower the thermal conductivity and improve the electric properties simultaneously. The 1.5at.% Bi doped Mg2Si0.4Sn0.6 got the maximum ZT of 0.91 at 600K.