Metal doping effects on the conduction type and the thermoelectric properties of beta;-FeSi2

Fe, Si and metal (Mn, Cu, Al) powders were mixed by ball-milling for 1 hour in an argon atmosphere. Mixtures of Fe, Si and metal (Mn, Cu, Al) powders were hot-pressed at 1373 K for 1 hour under 46.8 MPa and heat treated at 1123 K for 12 hours in an argon atmosphere. The conduction type of FeSix depends strongly on the composition ratio (x) of Si/Fe. The Seebeck coefficient at the composition range of 1.80a≤ x ≤2.08 is positive, but negative in the range of 2.10 ≤ x ≤ 2.30 in the temperature range 300-780 K. One metal doping (Cu or Al) to the FeSi2.06, enhanced the positive value of Seebeck coefficient (a) and that to the FeSi2.15, enhanced the negative value of α. On the other hand, both Mn doped FeSi2.06 and FeSi 2.15 showed the positive value of a. Doping effects of two metal elements (Mn-Cu, Mn-Al) to the FeSi2.06 were investigated. Doping of Mn-Al to the FeSi2.06 enhanced the Seebeck coefficient (a) and lowered the resistivity at high temperature range. The Seebeck coefficient of Mn-Al doped β-FeSi2 (Fe0.97Mn0.03Si 2.06Al0.05 showed the maximum value 279.15 [μV/K] at 773 [K]. β-FeSi2, hot-pressing, metal (Mn, Cu, Al) doping, thermoelectric properties.