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Polycrystalline Cr-doped higher manganese silicides (HMSs) Mn1- Cr Si-1.80 ( = 0 to 0.03) were prepared by the spark plasma sintering method. The phase structure and microstructure of the bulk samples were investigated, and their thermoelectric (TE) properties were measured from 473 K to 873 K. x-Ray diffraction patterns show that almost all of the Cr-doped samples possess single-phase HMS structure. However, minor amounts of MnSi phase can be observed in scanning electron microscopy images. The electrical conductivity increases continuously with increasing Cr substitution, and is enhanced by up to 15% for bulk Mn0.97Cr0.03Si1.80 over the entire measurement range from 473 K to 873 K. Meanwhile, the Seebeck coefficient is slightly depressed, so that the power factor is increased by about 10%. Cr doping affects the thermal conductivity negatively, and the overall dimensionless TE figure of merit of all the samples decreases slightly due to the higher thermal conductivity.
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