Electronic structures and thermoelectric properties of Sb-doped type-VIII clathrate Ba ₈Ga ₁₆Sn ₃₀

The type-VIII clathrate Ba ₈Ga ₁₆Sn ₃₀ shows a high figure of merit (ZT) in the middle temperature range 470-670 K. ZT enhancement through Sb doping has recently been reported in p-type Ba ₈Ga ₁₆Sn ₃₀. In this study, calculations to determine the electronic structures and thermoelectric properties of Sb-doped Ba ₈Ga ₁₆Sn ₃₀ are performed using the WIEN2k code. The energy derivative of density of states [∂ρ(ε)/ ∂ε] _ε=EF for valence band is lower in the Sb-doped Ba ₈Ga ₁₆Sn ₃₀ than in non-Sb-doped one, though the density of states [ρ(ε)] _ε-EF of both system are almost the same as that for Ba ₈Ga ₁₆Sn ₃₀. Except for the signs, the calculated Seebeck coefficients for the p- and n-type Sb-doped and non-Sb-doped Ba ₈Ga ₁₆Sn ₃₀ are similar.