Abstract
In the thermoelectric field, GeSe is a two-dimensional layered semiconductor with a large band gap, intrinsically low carrier concentration and poor thermoelectric figure of merit <i>ZT</i>. In this work, a series of GeSe<sub>1–<i>x</i></sub>Te<sub><i>x</i></sub> (<i>x</i> = 0, 0.05, 0.15, 0.25, 0.35, 0.45) polycrystalline samples is prepared by melting and quenching combined with spark plasma activation sintering process. The influences of Te content on the phase structure and thermoelectric transport properties of GeSe are systematically studied. The results indicate that with the increase of Te content, the crystal structure of GeSe gradually changes from orthorhombic to rhombohedral structure. This reduces the band gap of the material, and simultaneously increases the carrier concentration and mobility. Meanwhile, the energy band degeneracy of the compound increases significantly because of enhanced crystal symmetry in this process, thereby considerably improving the effective mass of carriers. Altogether, the power factor of the rhombohedral GeSe is increased by about 2 to 3 orders of magnitude compared with that of the orthorhombic phase GeSe. In addition, the rhombohedral phase GeSe has abundant cationic vacancy defects and softened phonons arising from its ferroelectric feature, leading the lattice thermal conductivity to be 60% lower than orthorhombic one. The GeSe<sub>0.55</sub>Te<sub>0.45</sub> sample achieves a peak <i>ZT</i> of 0.75 at 573 K, which is 19 times that of pristine GeSe. Crystal structure engineering could be considered as an effective way of improving the thermoelectric performance of GeSe compounds.
Highlights
The results indicate that with the increase of Te content, the crystal structure of GeSe gradually changes from orthorhombic to rhombohedral structure
采用熔融淬火结合放电等离子活化烧结工艺 制备了一系列的 GeSe1–xTex 样品, 并对样品的相 组成、微观结构以及热电性能进行测试表征, 得出 以下结论: 1) 随 Te 固溶量的增加, GeSe 样品的物相结 构发生改变
Summary
在本工作中, 采用熔融淬火结合放电等离子活化烧结工艺制备了一系列的 GeSe1–xTex (x = 0, 0.05, 0.15, 0.25, 0.35, 0.45) 多晶样品, 研究了 Te 含量对 GeSe 化合物物相结构和热电输运性能的影响规律. 当 Te 含量为 0.45 时, 样品在 573 K 取得最大热电优值 ZT 为 0.75, 是本征 GeSe 样品的 19 倍. 理论计算研究 表明, 在优化的载流子浓度 (~1019 cm–3) 的条件下, 正交相 GeSe 是一种极具潜力的中温热电材料, 在 300 K 和 800 K 预测的 ZT 值分别高达 0.8 和 2.5[7−9]. 图 2 GeSe1–xTex (x = 0—0.45) 样品的 (a) 粉末 XRD 图谱; (b) 28°—35°粉末 XRD 图谱; (c) 晶胞参数; (d) GeSe-GeTe 赝二元相图
Talk to us
Join us for a 30 min session where you can share your feedback and ask us any queries you have