Temperature dependence of thermoelectric power and resistivity was measured for the β-FeSi{sub}2 based east alloys on which n-type Co doping was performed with or without Cu addition. The Cu-free alloy shows a homogeneous eutectic microstructure consisting of metallic phases α-FeSi{sub}2 and ε-FeSi, while the Cu-doped alloy has a quite homogeneous microstructure dominated by coarse ε-FeSi dendrites in the α-FeSi{sub}2 matrix. Adequate heat treatment condition for the semiconductor β-FeSi{sub}2 phase formation has been evaluated as annealing at 923 K for less than 50 h, which is lower in temperature and shorter in duration than previously reported for alloys prepared by powder metallurgy. The resistivity measurement with the aid of microstructure observation has revealed that the β-FeSi{sub}2 formation takes place and almost finishes at very early stage of annealing process. Addition of Cu effectively promotes the β-FeSi{sub}2 formation rate of the present cast alloys.
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