Solid-State Synthesis and Thermoelectric Properties of Cr-doped MnSi1.75−δ

Cr-doped higher manganese silicides (HMS), MnSi 1.75− δ :Cr x ( δ = 0, 0.01, 0.02, 0.03, x = 0, 0.01), were synthesized by solid-state reaction and hot pressing. X-ray diffraction analysis and Rietveld refinement confirmed the synthesis of HMS; the amount of MnSi secondary phase was less than 1%. It was confirmed that Cr atoms were soluble in the HMS structure, because the lattice constant increased with increasing Cr content. p -Type conduction was observed for all specimens at all the temperatures investigated (323–823 K), and all the specimens had degenerate semiconductor characteristics, indicating that the electrical conductivity decreased and the Seebeck coefficient increased with increasing temperature. The power factors increased because the Seebeck coefficients decreased, and electrical conductivity was increased by Cr doping. The thermal conductivity was nearly independent of Cr doping. The maximum ZT obtained was 0.36 at 823 K for MnSi 1.73 :Cr 0.01 .