Composition dependence of thermoelectric properties of binary narrow-gap Ga67−xRu33+x compound

The composition and carrier concentration variations of the thermoelectric properties of the binary narrow-gap compound Ga67−xRu33+x have been investigated. The measured samples were synthesized by a combination of arc-melting and spark plasma sintering (SPS), succeeded in crack-free samples. We report that the temperature dependences of the electrical resistivity and Seebeck coefficient of the Ga67−xRu33+x are strongly affected by nominal Ru concentration. The Seebeck coefficients showed large positive values from 170 to 350 μV K−1 at 373 K. Also, large power factors from 2.2 to 3.0 mW m−1 K−2 were obtained at 773 K. The dimensionless figures of merit ZT beneficially increased with increasing temperature and reached a maximum value of 0.50 at about 773 K.

Research highlights▶ Ga67−xRu33+x compounds were synthesized by arc-melting and spark plasma sintering methods. ▶ Large power factors from 2.2 to 3.0 mW m−1 K−2 were obtained at 773 K. ▶ Maximum dimensionless figure of merit was 0.50 at 773 K for Ga66.6Ru33.4 compound.