am6b12297_si_001.pdf (800 kB)
Nano- and Microstructure Engineering: An Effective Method for Creating High Efficiency Magnesium Silicide Based Thermoelectrics
journal contribution
posted on 2016-11-24, 00:00 authored by Nader Farahi, Sagar Prabhudev, Gianluigi A. Botton, James R. Salvador, Holger KleinkeConsidering
the effect of CO2 emission together with the depletion
of fossil fuel resources on future generations, industries in particular
the transportation sector are in deep need of a viable solution to
follow the environmental regulation to limit the CO2 emission.
Thermoelectrics may be a practical choice for recovering the waste
heat, provided their conversion energy can be improved. Here, the
high temperature thermoelectric properties of high purity Bi doped
Mg2(Si,Sn) are presented. The samples Mg2Si1–x–ySnxBiy with x(Sn) ≥ 0.6 and y(Bi) ≥ 0.03
exhibited electrical conductivities and Seebeck coefficients of approximately
1000 Ω–1 cm–1 and −200
μV K–1 at 773 K, respectively, attributable
to a combination of band convergence and microstructure engineering
through ball mill processing. In addition to the high electrical conductivity
and Seebeck coefficient, the thermal conductivity of the solid solutions
reached values below 2.5 W m–1 K–1 due to highly efficient phonon scattering from mass fluctuation
and grain boundary effects. These properties combined for zT values of 1.4 at 773 K with an average zT of 0.9 between 400 and 773 K. The transport properties were both
highly reproducible across several measurement systems and were stable
with thermal cycling.