Electrical and microstructural analyses on the Co-doped FeSi2 prepared by vacuum hot pressing

Co-doped n-type FeSi₂ powders have been prepared by mechanical alloying and sintered by vacuum hot pressing. As-hot-pressed compacts were composed of untransformed mixture of α-Fe₂Si₅ and ε-FeSi phases. Vacuum annealing at 830°C led to the thermoelectric semiconducting β-FeSi₂ phase transformation, but some residual metallic α and ε phases were unavoidable. Electronic transport parameters and thermoelectric properties were remarkably changed by annealing due to the transformation from metallic α and ε phases to semiconducting β phases. Microstructural analysis was also carried out by using TEM.