Electronic Structures of Several Intermetallic Semiconductors for Expected Thermoelectric Applications: Alkaline-earth metal Pnictides, Iron group element Gallides and Indiumides, and Ir3Si5

We present the results of electronic structure calculations of Mg ₃Pn₂ (Pn: As, Sb, Bi), TA₃ (T: Fe, Ru, Os, A: Ga, In) and Ir₃Si₅ obtained by a first-principle pseudopotential method. The calculated band gaps are 0.41 eV for Mg₃Sb₂, 0.5 eV for FeGa₃, and 1.14 eV for Ir₃Si₅. These are narrower than the observed values in the case of Mg₃Sb₂ and Ir ₃Si₅, but wider for FeGa₃. In order to confirm the feasibility of band gap tuning of these semiconducting compounds by replacement of the constituent metallic elements by the elements belonging to the same group in the periodic table, calculations for Mg₃N₂, Mg₃P₂, Mg₃ As₂, Mg₃Bi₂, and Ca₃N ₂, or RuGa₃, OsGa₃ and RuIn₃ are also performed