Crystal structure and thermoelectric properties of β-MoSi2

A powder sample of a metastable phase β-MoSi2 having the C40-type crystal structure was prepared by heating Mo sheets with a Na–Si melt at 858 K for 12 h to determine details of the crystal structure. The lattice constants (a = 4.6016(3) Å and c = 6.5700(3) Å) and Si atom coordinate (y = 0.1658(2)) of β-MoSi2 were determined by Rietveld analysis of the X-ray powder diffraction. The thermoelectric properties were refined for a bulk sample prepared by sintering the β-MoSi2 powder at 773 K and 600 MPa. The electrical resistivity of the sintered β-MoSi2 sample with a relative density of 65% of the theoretical one was 2.5 mΩ cm at 300 K, and slightly increased with increasing temperature from 300 to 725 K. The Seebeck coefficients changed from +60 to +89 μV/K in the temperature range from 330 to 725 K. The maximum thermoelectric power factor was 2.2 × 10−6 W cm−1 K−2 at 725 K.

► Powder of β-MoSi2 (metastable phase) with C40-type structure is prepared by a preparation method using a Na–Si melt. ► The details of the crystal structure are experimentally determined. ► The Resistivity of the sintered sample shows metallic behavior and the Seebeck coefficient shows maximum value of +89 μV/K (725 K), which is over 10 times higher than that of α-MoSi2 (stable phase) with C11b-type structure.