Thermoelectric properties of Bi-doped Mg2Si semiconductors

The thermoelectric properties of Bi-doped Mg2Si (Mg2Si:Bi=1:x) fabricated by spark plasma sintering process have been characterized by Hall effect measurements at 300 K and by measurements of electrical resistivity (ρ), Seebeck coefficient (S), and thermal conductivity (κ) between 300 and 900 K. Bi-doped Mg2Si samples are n-type in the measured temperature range. The electron concentration of Bi-doped Mg2Si at 300 K ranges from 1.8×1019 cm−3 for the Bi concentration x=0.001 to 1.1×1020 cm−3 for x=0.02. The solubility limit of Bi in Mg2Si is estimated to be about 1.3 at% and first-principles calculation revealed that Bi atoms are expected to be primarily located at the Si sites in Mg2Si. The electrical resistivity, Seebeck coefficient, and thermal conductivity are strongly affected by the Bi concentration. The sample of x=0.02 shows a maximum value of the figure of merit, ZT, is 0.86 at 862 K.