Thermoelectric properties of FeGa3-type narrow-bandgap intermetallic compounds Ru(Ga,In)3: Experimental and calculational studies

The thermoelectric properties of polycrystalline binary narrow-bandgap intermetallic RuGa3 and RuIn3 compounds have been investigated in the temperature range from 373K to 973 K. These compounds exhibit semiconductor-like transport properties with large Seebeck coefficients of -560 mu V/K and 280 mu V/K at 373K for RuGa3 and RuIn3, respectively. The Seebeck coefficient of RuGa3 changed rapidly from large negative to large positive values around 500 K, which is consistent with our calculation based on the full-potential-linearized-augmented-plane-wave method. In contrast, RuIn3 is a p-type material at its operating temperature. The dimensionless figures of merit ZT of pure compounds reached maximum values of 0.13 and 0.17 at about 973K and 773 K, respectively. The potential maximum ZT value was evaluated using the Boltzmann transport equation and can exceed unity by electron- or hole-doping for both compounds. By substituting Co for Ru in RuIn3, n-type thermoelectric materials (ZT(max) = 0.10 at 473 K) were obtained. We suggest that ZT will be enhanced by further effective electron-doping. (C) 2012 American Institute of Physics. [http://dx.doi.org/10.1063/1.4729772]