Anisotropic Seebeck coefficient in β-FeSi2 single crystal

To discuss the possibility of improvement in thermoelectric properties of beta-FeSi2, we examined anisotropy of the Seebeck coefficient of the beta-FeSi2 using single crystal specimens grown by temperature gradient solution growth method. Polyhedral shaped bulk crystals with facet planes were obtained, and they were confirmed as single phase of beta-FeSi2 by X-ray diffraction measurements. For measurements of the Seebeck coefficient, we developed an apparatus that is capable of measuring the Seebeck coefficient of a small specimen down to a few mm in size, because commercially available apparatus cannot be used for such small specimens. The Seebeck coefficient measured along one direction on a surface was around 294 muV/K, while that measured along another direction perpendicular to the former one was 218 muV/K. The difference was larger than experimental error, and appeared to attribute to the difference in crystallographic direction. (C) 2004 Elsevier B.V. All rights reserved.