Thermoelectric Properties of Solution Grown &beta;-FeSi<SUB>2</SUB> Single Crystals

Abstract

We have measured the Seebeck coefficient of single crystalline -FeSi 2 grown by a temperature gradient solution growth (TGSG) method using Ga solvent. Rectangular-like -FeSi 2 plates with the size of ð3{6Þ Â ð1{2Þ Â 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 Â 10 À4 m and 2 Â 10 25 m À3 at room temperature (RT), respectively. The Seebeck coefficient measured along the [011] direction was approximately 350 mV/K at RT and showed the maximum value of 500 mV/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 Â 10 À4 Wm À1 K À2 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 Â 10 À4 Wm À1 K À2 around 150 K. The value was more than one order of magnitude larger than reported values.

Solution growth of n-type β-FeSi2 single crystals using Ni-doped Zn solvent

“…A large Seebeck coefficient is demonstrated from single crystalline b-FeSi 2 grown by a chemical vapor transport (CVT) and solution growth method [1,2]. Very recently, thermoelectric power factor P ( ¼ a 2 /r) of 3 Â 10 À4 Wm À1 K À2 , where a is the Seebeck coefficient and r the electrical resistivity, has been observed from solution-grown p-type b-FeSi 2 (Ga solvent) in temperatures between 100 and 300 K [2]. This value is more than one or two order of magnitude larger than that of sintered poly crystal (Mn-doped) [3] and more than three times larger than that of CVT-grown single crystal (Cr-doped) [1].…”