Si添加物对Li掺杂的Mg_2(Ge,Sn)热电性能的影响

The Influence of Si Addition on Li Doped Mg_2(Ge,Sn) Thermoelectric Properties

Mg_2(Ge,Sn)固溶体是一种环境友好型的中温(500~800 K)热电材料。目前n型Mg_2(Ge,Sn)热电材料的ZT值已经高达1. 4,但p型Mg_2(Ge,Sn)的ZT值仅为0. 5。本文在p型Mg1. 92Li0. 08Ge0. 4Sn0. 6中添加了少量Si元素以在材料中形成富Si相,利用其与基体的界面过滤低能载流子、降低热导率。采用两步固相反应、球磨和热压的方法制备Mg_(1.92)Li_(0.08)Ge_(0.4)Sn_(0.6-x)Si_x(x=0,0. 025,0. 05,0. 075,0. 1)样品,通过测试样品的热电输运参数,分析Si添加物对样品热电输运和性能的影响。结果表明:Si添加物能显著提高基体的功率因子,同时有效降低晶格热导率和电子热导率;最终,Mg1. 92Li0. 08Ge0. 4Sn0. 525Si0. 075的ZT最大值在723 K达到0. 75。

Mg 2（Ge,Sn） solid solutions are one of eco-friendly thermoelectric materials applied on mid-temperature （500～800 K）. Although dimensionless figure of merit ZT of n type Mg 2（Ge,Sn） has reached 1.4, the maxima ZT of p type Mg 2（Ge,Sn） is just 0.5 so far. In this paper, Si were added to p type Mg 1.92 Li 0.08 Ge 0.4 Sn 0.6 samples. The addition of Si results in Si-rich phase, which can create interface barrier to block low-energy carrier and reduce thermal conductivity. The samples of Mg 1.92 Li 0.08 Ge 0.4 Sn 0.6- x Si x （x =0,0.025,0.05,0.075,0.1） were fabricated by two-steps solid recreation, ball milling and hot-pressing, and their thermoelectric transport parameters were investigated, with specially analyzing the influence of Si addition on thermal conductivity. The results demonstrate that the Si addition observably improve the power factor, with the simultaneously decreasing of both the lattice thermal conductivity and the electrical thermal conductivity. Finally, the maximum figure of merit ZT of Mg 1.92 Li 0.08 Ge 0.4 Sn 0.525 Si 0.075 reaches 0.75 at 723 K.