Thermoelectric Properties of Solution Grown β-FeSi₂ Single Crystals

Abstract

We have measured the Seebeck coefficient of single crystalline β-FeSi₂ grown by a temperature gradient solution growth (TGSG) method using Ga solvent. Rectangular-like β-FeSi₂ plates with the size of (3–6)×(1–2)×0.3 mm³, where the longitudinal axis was [011], were prepared from the grown ingots. Typical resistivity and hole concentration of the crystals were 4×10⁻⁴ Ωm and 2×10²⁵ m⁻³ at room temperature (RT), respectively. The Seebeck coefficient measured along the [011] direction was approximately 350 μV/K at RT and showed the maximum value of 500 μV/K between 20 and 25 K. We also found that the solution grown single crystals had large power factors below RT. The value was 3.4×10⁻⁴ 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 4.5×10⁻⁴ Wm⁻¹ K⁻² around 150 K. The value was more than one order of magnitude larger than reported values.