Effect of Nanostructuring on the Thermoelectric Properties of β-FeSi2.

Linda Abbassi,Emmanuel Flahaut,Claude Estournès,Bhuvanesh Srinivasan,David Berthebaud,Geoffroy Chevallier,Takao Mori,David Mesguich,Sylvain Le Tonquesse,Mickaël Beaudhuin,Loïc Coulomb,Romain Viennois

doi:10.3390/nano11112852

Abstract

Nanostructured β-FeSi2 and β-Fe0.95Co0.05Si2 specimens with a relative density of up to 95% were synthesized by combining a top-down approach and spark plasma sintering. The thermoelectric properties of a 50 nm crystallite size β-FeSi2 sample were compared to those of an annealed one, and for the former a strong decrease in lattice thermal conductivity and an upshift of the maximum Seebeck’s coefficient were shown, resulting in an improvement of the figure of merit by a factor of 1.7 at 670 K. For β-Fe0.95Co0.05Si2, one observes that the figure of merit is increased by a factor of 1.2 at 723 K between long time annealed and nanostructured samples mainly due to an increase in the phonon scattering and an increase in the point defects. This results in both a decrease in the thermal conductivity to 3.95 W/mK at 330 K and an increase in the power factor to 0.63 mW/mK2 at 723 K.

Highlights

Global warming and the energy crisis have increased the interest in renewable and green energy sources
We investigated the effect of the nanostructuration on thermoelectric properties by combining a top-down approach coupled with Spark Plasma Sintering (SPS) on β-FeSi2 and one of the best Co-alloys β-Fe0.95 Co0.05 Si2
Analysis after 50 h of annealing the Rietveld refinement shows that β-FeSi2 ε-FeSi phases whereas ε-FeSi phases whereas after 50 h of annealing the Rietveld refinement shows that β-FeSi2 is obtained

Summary

Introduction

Global warming and the energy crisis have increased the interest in renewable and green energy sources. The efficiency is still limited for the thermogeneration of electricity compared to electricity produced by turbines [2], and most of the new thermoelectric materials, as well as the conventional materials, are made of rare, expensive and toxic elements such as chalcogen or pnictogen atoms or have stability problems [3,4,5]. To overwhelm these last problems, silicide intermetallics such as Mg2 Si1-x Snx , higher manganese silicides or β-FeSi2 were developed [6].

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Results

Conclusion