Phosphorus doping in n-type β-FeSi2/Si composites and its effects on thermoelectric properties

The influence of P substitution in Si within the n-type Co doped β-FeSi2/Si composites on the microstructure and thermoelectric properties were investigated. Thermoelectric performance components of Seebeck coefficient, electrical resistivity, and thermal conductivity were measured from 200 °C to 800 °C. Power factor and dimensionless figure of merit (ZT) were then evaluated within that temperature range. The electrical resistivity of Fe28.91Co0.59Si70.5-xPx after annealed at 800 °C for 4 h was reduced at x = 2.82 at% but increased at x = 4.23 at%. The Seebeck coefficient of Fe28.91Co0.59Si70.5-xPx after annealed at 800 °C for 4 h was negative, indicating that P atoms as an n-type dopant in the Si phase. The thermal conductivity of the P-doped at 2.82 at% sample was smaller than not only that of the non-doped composite but also the singular phase of β-FeSi2. ZT value was significantly enhanced by P doping as compared with that of the non-doped n-type β-FeSi2/Si composites.