Thermoelectric properties of β-FeSi2 with B4C and BN dispersion by mechanical alloying

Abstract

The B4C- and BN-dispersed β-FeSi2 thermoelectric materials were synthesized by mechanical alloying and subsequent hot pressing. The effects of the B4C and BN dispersion on the thermoelectric properties, such as Seebeck coefficient, electrical resistivity and thermal conductivity etc., of the β-FeSi2 were investigated. For the sample with B4C and BN addition, a larger amount of the residual ∈ phase was detected in the X-ray diffraction patterns than the sample without addition. In the case of the BN addition, the Seebeck coefficient was enhanced by BN addition above 700 K, and the electrical resistivity also increased with increasing amount of BN. This is considered to result from doping of a small amount of B into the β phase due to partial decomposition of the BN phase. The fine dispersion of BN particles in the β phase matrix was quite effective for reducing the thermal conductivity as compared to the B4C addition over the entire temperature range. The figure of merit, Z, of the β-FeSi2 was significantly enhanced by BN addition.