ae9b01426_si_001.pdf (906.4 kB)
Magnesioreduction Synthesis of Co-Doped β‑FeSi2: Mechanism, Microstructure, and Improved Thermoelectric Properties
journal contribution
posted on 2019-11-15, 15:38 authored by Sylvain Le Tonquesse, Zelia Verastegui, Hélène Huynh, Vincent Dorcet, Quansheng Guo, Valérie Demange, Carmelo Prestipino, David Berthebaud, Takao Mori, Mathieu Pasturelβ-FeSi2 and β-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 β-Co0.07Fe0.93Si2.