High figure of merit and thermoelectric properties of Bi-doped Mg2Si0.4Sn0.6 solid solutions

Abstract The study of Mg2Si1−xSnx-based thermoelectric materials has received widespread attention due to a potentially high thermoelectric performance, abundant raw materials, relatively low cost of modules, and non-toxic character of compounds. In this research, Mg2.16(Si0.4Sn0.6)1−yBiy solid solutions with the nominal Bi content of 0≤y≤0.03 are prepared using a two-step solid state reaction followed by spark plasma sintering consolidation. Within this range of Bi concentrations, no evidence of second phase segregation was found. Bi is confirmed to occupy the Si/Sn sites in the crystal lattice and behaves as an efficient n-type dopant in Mg2Si0.4Sn0.6. Similar to the effect of Sb, Bi doping greatly increases the electron density and the power factor, and reduces the lattice thermal conductivity of Mg2.16Si0.4Sn0.6 solid solutions. Overall, the thermoelectric figure of merit of Bi-doped Mg2.16Si0.4Sn0.6 solid solutions is improved by about 10% in comparison to values obtained with Sb-doped materials of comparable dopant content. This improvement comes chiefly from a marginally higher Seebeck coefficient of Bi-doped solid solutions. The highest ZT∼1.4 is achieved for the y=0.03 composition at 800 K.

[1]  Y. Imai,et al.  The effect of Bi doping on thermoelectric properties of Mg2Si0.5Sn0.5 , 2007, 2007 26th International Conference on Thermoelectrics.

[2]  M. Kanatzidis,et al.  High-performance bulk thermoelectrics with all-scale hierarchical architectures , 2012, Nature.

[3]  Nack J. Kim,et al.  Thermodynamic modeling of the Mg–Si–Sn system , 2007 .

[4]  N. Otsuka,et al.  Preparation and Thermoelectric Properties of Mg2Si1−xGex (x=0.0∼0.4) Solid Solution Semiconductors , 1992 .

[5]  Xinbing Zhao,et al.  Enhanced thermoelectric properties of Mg2Si0.58Sn0.42 compounds by Bi doping , 2012 .

[6]  C. Uher,et al.  Optimized Thermoelectric Properties of Sb-Doped Mg2(1+z)Si0.5–ySn0.5Sby through Adjustment of the Mg Content , 2011 .

[7]  Heng Wang,et al.  Convergence of electronic bands for high performance bulk thermoelectrics , 2011, Nature.

[8]  E. A. Gurieva,et al.  Highly effective Mg 2 Si 1 − x Sn x thermoelectrics , 2006 .

[9]  Sossina M. Haile,et al.  Zintl Phases as Thermoelectric Materials: Tuned Transport Properties of the Compounds CaxYb1–xZn2Sb2 , 2005 .

[10]  C. Uher,et al.  Enhanced thermoelectric properties of n-type Mg2.16(Si0.4Sn0.6)1−ySby due to nano-sized Sn-rich precipitates and an optimized electron concentration , 2012 .

[11]  Eric S. Toberer,et al.  Mechanochemical synthesis and thermoelectric properties of high quality magnesium silicide , 2011 .

[12]  D. Rowe.  CRC Handbook of Thermoelectrics , 1995 .

[13]  Q. Shen,et al.  Preparation and Thermoelectric Properties of Bi-Doped Mg2Si0.8Sn0.2 Compound , 2010 .

[14]  Jun-ichi Tani,et al.  Thermoelectric properties of Bi-doped Mg2Si semiconductors , 2005 .

[15]  H. Goldsmid,et al.  Estimation of the thermal band gap of a semiconductor from seebeck measurements , 1999 .

[16]  J. Tani,et al.  First-principles and experimental studies of impurity doping into Mg2Si , 2008 .