High Performance Mg2(Si, Sn) Solid Solutions: a Point Defect Chemistry Approach to Enhancing Thermoelectric Properties. (1st April 2014)

• Record Type: Journal Article
• Authors: Jiang, Guangyu; He, Jian; Zhu, Tiejun; Fu, Chenguang; Liu, Xiaohua; Hu, Lipeng; Zhao, Xinbing
• Is Part Of: Advanced functional materials. Volume 24:Number 24(2014)
• Page Start: 3776
• Page End: 3781
• Publication Date: 2014-04-01
• Subjects: Materials -- Periodicals; Chemical vapor deposition -- Periodicals; 620.11
• DOI: 10.1002/adfm.201400123
• Languages: English
• ISSNs: 1616-301X

Abstract

<abstract abstract-type="main" xml:lang="en"> <title> <x xml:space="preserve">Abstract</x> </title> <p>A point defect chemistry approach to improving thermoelectric (TE) properties is introduced, and its effectiveness in the emerging mid‐temperature TE material Mg<sub>2</sub>(Si, Sn) is demonstrated. The TE properties of Mg<sub>2</sub>(Si, Sn) are enhanced via the synergistical implementation of three types of point defects, that is, Sb dopants, Mg vacancies, and Mg interstitials in Mg<sub>2</sub>Si<sub>0.4</sub>Sn<sub>0.6‐<italic>x</italic></sub>Sb<italic><sub>x</sub></italic> with high Sb content (<italic>x</italic> > 0.1), and it is found that i) Sb doping at low ratios tunes the carrier concentration while it facilitates the formation of Mg vacancies at high doping ratios (<italic>x</italic> > 0.1). Mg vacancies act as acceptors and phonon scatters; ii) the concentration of Mg vacancies is effectively controlled by the Sb doping ratio; iii) excess Mg facilitates the formation of Mg interstitials that also tunes the carrier concentration; vi) at the optimal Sb‐doping ratio near <italic>x</italic> ≈ 0.10 the lattice thermal conductivity is significantly reduced, and a state‐of‐the‐art figure of merit ZT > 1.1 is attained at 750 K in 2 at% Zn doped Mg<sub>2</sub>Si<sub>0.4</sub>Sn<sub>0.5</sub>Sb<sub>0.1</sub> specimen. These results demonstrate the significance of point defects in thermoelectrics, and the promise of point defect chemistry as a new approach in optimizing TE properties.</p> </abstract>