Microstructure and THERMOELECTRIC PROPERTIES OF DOPED FeSi2 WITH ADDITION OF B4C NANOPARTICLES

Abstract

β-FeSi2 with the addition of B4C nanoparticles was manufactured by sintering mechanically alloyed Fe and Si powders with Mn, Co, Al, P as p and n-type dopants. The consolidated samples were subsequently annealed at 1123 K for 36 ks. XRD analysis of sinters after annealing confirmed nearly full transformation from α and ε into thermoelectric β-FeSi2 phase. SEM observations of samples surface were compliant with the diffraction curves. TEM observations allowed to depict evenly distributed B4C nanoparticles thorough material, with no visible aggregates and establish grain size parameter d2 < 500 nm. All dopants contributed to lower thermal conductivity and Seebeck coefficient, with Co having strongest influence on increasing electrical conductivity in relation to reference FeSi2. Combination of the addition of Co as dopant and B4C nanoparticles as phonon scatterer resulted in dimensionless figure of merit ZT reaching 7.6 × 10-2 at 773 K for Fe0.97Co0.03Si2 compound. Comparison of the thermoelectric properties of examined sinters to the previously manufactured of the same stoichiometry but without B4C nanoparticles revealed theirs overall negative influence.