Improved Thermoelectric Properties of Fe Doped Si-Rich Higher Manganese Silicide

Pure and Fe doped Si-rich MnSi1.8 samples have prepared by induction melting followed by induction hot-pressing. Powder X ray diffraction pattern has confirmed the phase purity with solid solubility of Fe in MnSi1.8. Further, FE SEM micrograph and elemental mapping using EDS have evidenced the presence of excess Si in the matrix of HMS and the elemental homogeneity of MnSi1.8, respectively. Upon Fe doping, the electrical conductivity, sigma decreases due to reduction in carrier concentration, whereas Seebeck coefficient, S subsequently increases. Importantly, doping of Fe and presence of Si in MnSi1.8 strongly scatter the low- and mid-wavelength phonons and reduces the lattice thermal conductivity to similar to 1.7 W/mK at 773 K, which led to the improved zT of similar to 0.50 at 773 K for the composition of Mn0.90Fe0.10Si1.8. Additionally, sample of Mn0.90Fe0.10Si1.8 has shown the higher hardness of similar to 11.57 GPa than the pure MnSi1.8 (similar to 5.81 GPa).