Thermoelectric properties of solution grown β-FeSi2 single crystals

We have measured the Seebeck coefficient of single crystalline beta-FeSi2 grown by a temperature gradient solution growth (TGSG) method using Ga solvent. Rectangular-like beta-FeSi2 plates with the size of (3-6) x (1-2) x 0.3 mm(3), where the longitudinal axis was [011], were prepared from the grown ingots. Typical resistivity and hole concentration of the crystals were 4 x 10(-4) Omega m and 2 x 10(25) m(-3) at room temperature (RT), respectively. The Seebeck coefficient measured along the [011] direction was approximately 350 mu V/K at RT and showed the maximum value of 500 mu V/K between 20 and 25 K. We also found that the solution grown single crystals had large power factors below RT. The value was 3.4 x 10(-4) Wm(-1) K-2 at RT, which was about three times larger than that of sintered poly-crystals and CVT-grown single crystals. The maximum power factor was 4.5 x 10(-4) Wm(-1) K-2 around 150 K. The value was more than one order of magnitude larger than reported values.