Abstract
Thermoelectric generation has drawn world wide attention to convert thermal energy into electrical energy. There are two factors evaluating thermoelectric properties, one is effective maximum power (Peff) and the other is maximum conversion efficiency (η max). The reduction in thermal conductivity (K) increases the temperature difference across a thermoelectric material (Δ T) located between heat source and sink. The increase in Δ T increases the Seebeck potential and hence Peff. The reduction in K increases the figure of merit (Z) and then increases η max. As a whole the reduction of K increases Peff as well as η max.
The substantial improvement of thermoelectric properties can be expected by using composite which consist of a thermoelectric material and a good conductor. Simple calculation made under the assumption that α = f⋅α (Cu)+(1-f)⋅α(β), 1 / ρ = f / ρ (Cu)+(1-f) / ρ (β), K=f⋅K(Cu)+(1-f)⋅K(β) indicates that Peff and η max of β-FeSi2 and Cu composite with a few vol% of Cu can be 24 and 12 times larger than those of β-FeSi2. Here, f is volume fraction of Cu, α (Cu) and α(β) are seebeck coefficient, ρ (Cu) and ρ (β) are specific resistance, K(Cu) and K(β) are thermal conductivity of Cu and β- FeSi2, respectively.
