Effect of Al-doping on suppression of thermal conductivity in Si dispersed β-FeSi2.

Silicon dispersed β -FeSi 2 with different aluminium concentrations are synthesized using eutectoid decomposition of α -Fe 2 Si 5− x Al x (0 ≤ x ≤ 0.1). Phase fractions, microstructure and thermoelectric properties of the above compositions have been investigated. Al-doping in Si dispersed β -FeSi 2 results in increased hole-carrier concentration thereby enhancing the electrical conductivity without compromising the Seebeck coefficient. This results in maximum power factor value of 4.7 μ Wcm −1 K −2 at 773 K for the sample with x = 0.1 which is significantly higher than that of an undoped sample. The thermal conductivity of the samples was fitted with the Debye-Callaway model to understand the various scattering processes involved. The analysis shows that an increased point defect scattering of phonons with Al-doping in addition to scattering by Si/ β -FeSi 2 interface lowers the thermal conductivity significantly. [ABSTRACT FROM AUTHOR]