Ziming Zhang,Chen Ming,Qingfeng Song,Lei Wang,Hanbing Chen,Jincheng Liao,Chao Wang,Lidong Chen,Shengqiang Bai
Mg 3 (Sb,Bi) 2 -based Zintl compounds are rising stars with superior features of high thermoelectric (TE) performance, nontoxicity and low cost. However, the poor thermodynamic stability hinders its practical application. Here, we propose a design strategy of modulating the local chemical composition with grain boundary (GB) phase guided by computational phase equilibrium diagrams. By in-situ constructing ZrSb 1- x second phase in the GB regions of Mg 3 (Sb,Bi) 2 -based compounds, the migration of Mg is blocked and the Mg deletion is depressed. Benefit from these, the driving force of Mg diffusion from matrix to GB and Mg migration along GBs is weakened, resulting in an improved thermal stability without degradation of electrical transport properties. The fabricated 8-pair TE module using GB modulated n-type Mg 3.1 Sb 1.5 Bi 0.49 Te 0.01 and p-type Ge 0.89 Cu 0.06 Sb 0.08 Te presents an efficiency of 8.9 % under the temperature difference of 450 K and shows excellent durability in the thermal cycling test. This study provides an effective strategy to improve thermal stability by constructing GB phase, and proves the feasibility of the practical application for Mg 3 Sb 2 -based TE modules.
Ziming Zhang,Zhiqiang Gao,Tingting Deng,Qingfeng Song,Lidong Chen,Shengqiang Bai
Mg3(Sb,Bi)2-based Zintl compounds have attracted lots of attention due to their high thermoelectric performance and good mechanical properties. However, thermally activated mobility, which is ascribed to the grain boundary scattering, greatly limits their practical use. In this work, we reveal the plasticity of Mg3(Sb,Bi)2-based compounds in the compressive strength test. The ab initio analysis indicates that this plasticity should be ascribed to the low slip barrier energy (∼580 mJ m−2), which is only one third of the cleavage energy (∼1600 mJ m−2). Based on this finding, we propose a cold-deformation procedure to elongate particles and to enhance texture, which successfully suppresses the grain boundary scattering. As a result, a high carrier mobility of 86.6 cm2 V−1 s−1 and a high power factor of 16.2 μW cm−1 K−2 in Mg3.1Bi1.5Sb0.49Te0.01 are obtained at room temperature. The plastic deformation capacity of Mg3(Sb,Bi)2 compounds provides a near-net-forming method to fabricate special-shaped devices at room-temperature, which will extend the application fields of thermoelectric techniques.
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