Microstructure and the anisotropic thermoelectric properties of β-FeSi₂ sintered under high-pressure

β-FeSi₂ was sintered under high-pressure/ temperature conditions of 3 GPa and 700-1400°C for 30 min using a belt-type high-pressure equipment. The material showed anisotropy due to heterogeneous distribution of pressure, however, the X-ray diffraction analysis did not reveal crystallographic orientation. The microstructure showed grain orientation along the direction perpendicular to the pressing direction. Such orientation was remarkable in the sample solidified from the melt. It was suggested that the development of microstructure was important factor in optimizing the thermoelectric properties. The formation and the phase stability of β-FeSi₂ under high-pressure condition were also discussed.