Mg含量对Mg3(1+z)Sb_(2)化合物热电传输性能的影响

Effect of Mg Content on Thermoelectric Property of Mg3_((1+z))Sb_(2) Compounds

Mg_(3)Sb_(2)化合物具有良好的热电性能和成本优势,受到研究者的广泛关注。由于Mg元素具有很高的饱和蒸汽压和化学反应活性,因此Mg_(3)Sb_(2)在合成过程中含量难以精确控制。本研究利用固相反应/球磨结合放电等离子体烧结制备了不同Mg含量的Mg_(3(1+z))Sb_(2)(z=0,0.02,0.04,0.06和0.08)样品,通过物相结构分析和热电性能测试,研究了Mg含量对Mg_(3)Sb_(2)化合物热电性能的影响规律。结果表明,随着名义Mg含量的增加,实际Mg含量在Mg_(3)Sb_(2)化合物中由缺失状态转变为过量状态,Mg_(3(1+z))Sb_(2)(z=0,0.02,0.04)样品存在Mg空位(V″_(Mg)),表现为p型传导;而Mg_(3(1+z))Sb_(2)(z=0.06,0.08)样品中存在间隙Mg(Mg_(i)^(..)),表现为n型传导。Mg3_((1+0.04))Sb_(2)样品在较宽温区(室温至770 K)内保持最高的热电优值,该样品最接近本征p型Mg_(3)Sb_(2)化合物的组成和热电性能。本研究表明,Mg含量对Mg_(3(1+z))Sb_(2)化合物载流子类型和浓度以及迁移率具有一定的调控作用。

Mg_(3)Sb_(2) compound has attracted much attention due to the promising thermoelectric properties and cost advantage.However,it is quite difficult to control Mg content during synthesizing processes because of high saturation vapor pressure and chemical reactivity of Mg element.Herein,Mg_(3(1+z))Sb_(2)(z=0,0.02,0.04,0.06 and 0.08)samples were prepared by combination of solid state reaction,ball milling and spark plasma sintering(SPS).Their effects of Mg content on thermoelectric properties of Mg_(3)Sb_(2) compounds were investigated in this study.Results indicate that actual Mg content rises with nominal Mg content increasing,and their point defect type changes from Mg vacancy(V''Mg)to interstitial Mg(Mg_(i)^(..)),leading to transition of transport behavior from p type(hole carriers predominated)for Mg_(3(1+z))Sb_(2)(z=0,0.02,0.04)samples to n type(electron carriers predominated)for Mg_(3(1+z))Sb_(2)(z=0.06,0.08)samples.Besides,Mg3_((1+0.04))Sb_(2) sample shows the highest ZT value from room temperature to 770 K,and achieves maximum ZT of 0.28 at 800 K.Additionally,Mg3_((1+0.04))Sb_(2) sample exhibits intrinsic p-type transport behavior for Mg_(3)Sb_(2) compound,which could serve as matrix to be extrinsically doped in the future study for further improvements of electrical properties and ZT value.