Electrical and microstructural analyses on the Co-doped FeSi/sub 2/ prepared by vacuum hot pressing

Co-doped n-type FeSi/sub 2/ powders have been prepared by mechanical alloying and sintered by vacuum hot pressing. As-hot-pressed compacts were composed of untransformed mixture of /spl alpha/-Fe/sub 2/Si/sub 5/ and /spl epsiv/-FeSi phases. Vacuum annealing at 830/spl deg/C led to the thermoelectric semiconducting /spl beta/-FeSi/sub 2/ phase transformation, but some residual metallic /spl alpha/ and /spl epsiv/ phases were unavoidable. Electronic transport parameters and thermoelectric properties were remarkably changed by annealing due to the transformation from metallic /spl alpha/ and /spl epsiv/ phases to semiconducting /spl beta/ phases. Microstructural analysis was also carried out by using TEM.