Thermoelectric property and microstructure of iron-silicide doped with Co and Ag

β-FeSi₂ is enumerated as a prospective material for thermoelectric conversion as well as photoelectric conversion and light emitting. In this paper, thermoelectric property and microstructure of β-FeSi₂ sintered with Ag were investigated by the measurements of Seebeck coefficient, electrical resistivity, X-ray diffraction and transmission electron microscopic observation. α-FeSi and ε-FeSi₂ were observed in an as-cast sample. β-FeSi₂ was produced by transformation from α-FeSi and ε-FeSi₂ after annealing at 1073K. β-FeSi₂ hardly contained Ag but contained Co as a dopant. Ag precipitated in the boundaries of β-FeSi₂ grains and between particles. Power factor was enhanced by Ag addition because of the large decrease in electrical resistivity and the slight decrease in Seebeck coefficient. The distribution of Ag was important factor for the power factor. The relation between microstructures and thermoelectric properties was revealed.