Influence of secondary phase dispersants and porosity on thermoelectric properties of β-Fe0.91Mn0.09Si2

Mn doped β-FeSi2 has been prepared by arc melting followed by hot pressing technique. The effect of porosity on thermovoltage (ΔV) and electrical conductivity is studied, where the band type conduction is noticed in β-FeSi2. The influence of dispersants on electrical transport has been studied by incorporation of secondary phase dispersants like SiC, NiO and YSZ. High ΔV of ∼90 mV at 925 K is achieved in 8% SiC dispersed β-Fe0.91Mn0.09Si2, while, the dense β-Fe0.91Mn0.09Si2 and porous β-Fe0.91Mn0.09Si2 have ΔV values of ∼54 and 78 mV, respectively. This enhanced ΔV is reliant on porosity and amount of secondary phase dispersant. Enhanced power outputs in porous (∼300%), 4% YSZ (∼160%), and 8% SiC (∼125%) β-Fe0.91Mn0.09Si2 as compared to dense β-Fe0.91Mn0.09Si2 are observed at 1000 K. The appropriate dispersant and porosity have enhanced the thermoelectric properties. Further, the activation energy and Lorentz number are considered to study the influence of porosity/dispersant as well as to understand the nature of disorder.