Thermoelectric properties of the Co-doped β-FeSi2 mixed with Ag

The Co-doped β-FeSi2 ingots, ribbons, or discs, which were mixed with Ag, were fabricated by conventional melting and cooling, spin-casting, or powdering and sintering. The microstructures and thermoelectric properties were investigated by using a transmission electron microscope, an energy dispersion X-ray micro-analyzer and measuring the Seebeck coefficient, electrical conductivity.The Ag phase was observed at the grain boundaries and the matrix of the β phase in the ingots, ribbons, discs. Ag was detected not to dissolve in the lattice of the β phase. The Seebeck coefficient decreases nonlinearly with increasing the amount of Ag. The Seebeck coefficient is large in the ribbon with the small amount of Ag. The electrical conductivity increases nonlinearly with increasing the amount of Ag. The electrical conductivity is large in the discs. The power factor reaches to a maximum and then decreases with increasing the amount of Ag. Mixing with Ag in the Co-doped β-FeSi2 is effective to improve the power factor of the discs.