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,并对其微观结构和熟电性能进行了表征.结果表明,MgH2替代传统原料Mg粉显著降低了圃相反应温度且防止了M8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200 nm的高纯产物.在300～750 K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600 K时,含1.5％Bi(原子分数)的Mg2Si0.4Sn0.6热电材料具有最大ZT值0.91.
The Bi doped Mg2Si1-xSnx (0.4≤x≤0.6) solid solution thermoelectric material with high purity was synthesized by microwave-assisted solid state reaction followed by field activated and pressure assisted synthesis (FAPAS),and its microstructure and transport properties were characterized.Results show 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 restrains the grain growth effectively;as a result,the pure product with an average grain size of 200 nm has been obtained.Thermoelectric performance was tested in the temperature range of 300～750 K.It is indicated 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 1.5 at％ Bi doped Mg2Si0.4Sn0.6 gets the maximum ZT of 0.91 at 600 K.
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