Structural stability enables high thermoelectric performance in room temperature Ag2Se,Journal of Materials Chemistry A

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Structural stability enables high thermoelectric performance in room temperature Ag2Se
Journal of Materials Chemistry A ( IF 10.7 ) Pub Date : 2020-05-28 , DOI: 10.1039/d0ta02614j
Priyanka Jood _{1,

2,

3,

4} , Raju Chetty _{1,

2,

3,

4} , Michihiro Ohta _{1,

2,

3,

4}

Affiliation

Ag₂Se is considered as an attractive candidate for use in room-temperature thermoelectric applications owing to its unique transport properties, such as glass-like thermal conductivity and good electrical conductivity. However, understanding the correlation between composition (Ag/Se ratio), defect structure, and transport properties is an important prerequisite to optimize its figure of merit (ZT). Using in-depth microscopic analysis, this study reveals the coexistence of a metastable and the main orthorhombic crystal structure in stoichiometric Ag₂Se. The formation of the metastable structure was found to be detrimental to the transport properties of bulk Ag₂Se. We were able to successfully inhibit its formation and stabilize the main orthorhombic structure via small anion (Se and S) excess. The compositions Ag₂SeCh_y (y ≤ 0.01; Ch = Se, S) yielded 40–70% rise in carrier mobility with a value of 2510 cm² V⁻¹ s⁻¹ at 300 K and extremely low lattice-thermal-conductivity (0.2–0.1 W m⁻¹ K⁻¹ over 300–375 K). This combination of transport properties yielded a room-temperature power factor of 3.2 mW m⁻¹ K⁻² and a nearly flat ZT value of ∼1.0 over the 300–375 K temperature range. Additionally, a record-high conversion efficiency (η_max) of 3.7% was theoretically obtained for single-leg Ag₂Se for a small temperature gradient of ∼80 K.

中文翻译：

结构稳定性可在室温下实现高热电性能Ag2Se

Ag ₂ Se由于其独特的传输特性（如玻璃般的导热性和良好的导电性）而被认为是在室温热电应用中有吸引力的候选物。但是，了解组成（Ag / Se比），缺陷结构和传输性能之间的相关性是优化其品质因数（ZT）的重要前提。使用深入的显微镜分析，这项研究揭示了化学计量的Ag ₂ Se中亚稳态和主要正交晶体结构的共存。发现亚稳结构的形成不利于块状Ag ₂的传输性质。硒我们能够通过少量过量的阴离子（Se和S）成功抑制其形成并稳定主要的正交结构。该组合物的Ag ₂ SECH _ý（Ý ≤0.01; CH =硒，S）得到的载流子迁移40-70％上升与2510厘米值² V ^-1小号^-1在300K和极低的晶格导热性（在300-375 K范围内为0.2-0.1 W m ^-1 K ^-1）。传输特性的这种组合产生了3.2 mW m ^-1 K ^-2的室温功率因数和几乎平坦的ZT在300–375 K的温度范围内，该值约为1.0。另外，记录的高转换效率（η_最大理论上得到的3.7％）为单腿的Ag ₂硒为〜80 K的小的温度梯度

更新日期：2020-07-07

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