定向凝固Ag掺杂Mg_(3)Sb_(2)合金热电性能  

Thermoelectric Properties of Directionally Solidified Ag-Doped Mg_(3)Sb_(2) Alloys

作　　者：张亚龙 李鑫[1] 谢辉[1] 魏鑫 Zhang Yalong;Li Xin;Xie Hui;Wei Xin(Xi’an Aeronautical University,Xi’an 710077,China)

机构地区：[1]西安航空学院,陕西西安710077

出　　处：《稀有金属材料与工程》2023年第2期544-550,共7页Rare Metal Materials and Engineering

基　　金：国家自然科学基金青年项目(51904219);陕西省自然科学基金青年项目(2020JQ-906)。

摘　　要：通过定向凝固方法可以高效制备Mg_(3)Sb_(2)晶体,根据凝固理论计算了平界面生长临界速率,在此速率下可以有效抑制第二相Sb的析出。对不同的凝固速率下的Mg_(3)Sb_(2)晶体微观组织进行了分析,表明凝固速率为5μm·s-1时可以有效减少Mg空位的出现,并在晶体中获得过量Mg原子,有利于更好地提升热电性能。通过消除晶界和Ag元素掺杂有效提升了Mg_(3)Sb_(2)晶体的载流子迁移率和浓度,在测试温度区间(300~800K)内,最大电导率值可达309S·cm^(-1),同时保持了较高的Seebeck系数值,从而获得了更好的电子传输性能(PF_(max)=1.2mW·m^(-1)·K^(-2)),通过Hall测试和第一性原理计算对此结果进行了验证。Ag掺杂浓度为2.5at%下相应的热电优值最高可以达到0.67,此方法为Mg_(3)Sb_(2)基热电材料性能优化提供了新的路径,也为制备高性能的Mg3(Sb, Bi)2三元合金提供参考。Mg_(3)Sb_(2)crystals were successfully prepared by directional solidification method. The critical velocity of planar interface of single-phase Mg_(3)Sb_(2)crystal was predicted according to the solidification theory, and the precipitated Sb phase can be inhibited below this rate. Microstructure analysis of Mg_(3)Sb_(2)crystals at different solidification rates indicates that, the quantity of Mg vacancies can be effectively reduced. The excess Mg atoms in the crystals is conducive to the improvement of thermoelectric performance. Carrier mobility and concentration of Mg_(3)Sb_(2)crystal is increased by grain boundary eliminated and Ag doping. On the premise of keeping a high Seebeck coefficient, the maximum electric conductivity is 309 S·cm^(-1)at the testing temperature range of 300-800 K. As a result, a better electronic transport properties of PF=1.2 mW·m^(-1)·K^(-2)is obtained.This result is verified by Hall testing and first-principle calculations. Correspondingly, the maximum ZT value is 0.67 at the doping concentration of 25at%. This method developed in this research provides a new path for the performance optimization of Mg_(3)Sb_(2)-based thermoelectric materials,and also provides a reference for the preparation of high-performance ternary Mg3(Sb, Bi)2alloy.

关 键 词：定向凝固 晶体生长 热电材料 Mg_(3)Sb_(2) 

分 类 号：TB34[一般工业技术—材料科学与工程]