Solid-state synthesis and thermoelectric properties of Al-doped MnSi1.73
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Al-doped HMSs (higher-manganese silicides), MnSi1.73:Alx (x = 0, 0.001, 0.0025, 0.005, 0.0075), were prepared by using a solid-state reaction and hot pressing. X-ray diffraction analysis and Rietveld refinement confirmed the synthesis of the HMSs, and the phase fractions of the HMSs with various Al contents (x) had no significant difference. A secondary phase (MnSi) in an amount of less than 1% appeared, which is less than the detection limit of the X-ray diffraction analysis. The Al atoms were confirmed to be soluble in the HMS structure because the lattice constant increased with increasing Al content. All specimens showed p-type conduction at all temperatures examined (323–823 K) and exhibited degenerate semiconductor characteristics, indicating that the electrical conductivity decreased and the Seebeck coefficient increased with increasing temperature. The electrical conductivity and the thermal conductivity were increased, and the Seebeck coefficients were decreased slightly by Al doping. The maximum dimensionless thermoelectric figure of merit ZT max was obtained as 0.41 at 823 K for MnSi1.73:Al0.005 due to its increased power factor.
KeywordsThermoelectric Higher manganese silicide Solid-state reaction Hot pressing
PACS numbers72.15.Jf 72.20.Pa
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