Journal
ACS APPLIED ENERGY MATERIALS
Volume 2, Issue 12, Pages 8525-8534Publisher
AMER CHEMICAL SOC
DOI: 10.1021/acsaem.9b01426
Keywords
iron silicide; thermoelectrics; magnesiothermy; mesostructure; stacking faults; thermal conductivity
Funding
- European Union
- CREST [JPMJCR15Q6]
- JSPS KAKENHI [JP17H02749, JP16H06441]
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beta-FeSi2 and beta-Co0.07Fe0.93Si2 thermoelectric silicides were synthesized from Fe2O3 and Si powders using a magnesiothermic process. Detailed study of the reaction mechanism by X-ray diffraction reveals that liquid Mg is mandatory to initiate the reduction. After completion of the reaction in relatively short time (10 h at 1173 K), the magnesiosynthesized iron disilicides are characterized as powders with grain sizes ranging from 30 to 400 nm and containing a high concentration of stacking faults quantified for the first time using a dedicated refinement software. The thermoelectric properties of spark plasma sintered pellets with submicrometric grain sizes, high stacking fault density, and residual micro- to nanoporosities are presented and compared to corresponding materials synthesized by conventional arc-melting process. Strong thermal conductivity reduction of 20% at 773 K has been achieved thanks to the mesostructure induced by the magnesioreduction. This results in an improved maximum figure-of-merit ZT reaching 0.18 at 773 K for beta-Co0.07Fe0.93Si2.
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