2013 Volume 54 Issue 6 Pages 953-957
The effects of substituting transition metals (TM: Co, Rh, Ni and Pd) on the Ru site with respect to the electrical conductivity and Seebeck coefficient for the binary semiconducting intermetallic compound RuGa2 have been investigated above room temperature. Only Rh substituted RuGa2 exhibited a higher electrical conductivity compared with undoped RuGa2. The sign of the Seebeck coefficient at 373 K for all doped samples is negative and their magnitudes exhibit rather large values of 150 < |S373K| < 350 µVK−1, indicating that Co, Rh, Ni and Pd work as n-type dopants. However, the sign changes from negative to positive at high temperature. This implies that the effective carrier doping is insufficient to obtain a high efficiency n-type material. To investigate the effect of TM substitution on the electronic density of states, the Korringa-Kohn-Rostoker Green’s function method under a coherent potential approximation has been employed. The calculation indicates that the dopant d-states at the conduction band affect the transport properties.
