High Temperature Electronic and Thermal Transport Properties of EuGa2-x In (x) Sb-2

The Zintl phase EuGa2Sb2 was synthesized via ball milling followed by hot pressing. The crystal structure of EuGa2Sb2 is comprised of a 3-D network of polyanionic [Ga2Sb2](2-) tunnels filled with Eu cations that provide charge balance (Eu2+[Ga2Sb2](2-)). Here we report the temperature-dependent resistivity, Hall Effect, Seebeck coefficient and thermal conductivity for EuGa2-x In (x) Sb-2 (x = 0, 0.05, 0.1) from 300 K to 775 K. Experimental results demonstrate that the material is a p-type semiconductor. However, a small band gap (similar to 0.1 eV) prevents EuGa2Sb2 from having high zT at higher temperatures. Isoelectronic substitution of In on the Ga site leads to point defect scattering of holes and phonons, thus reducing thermal conductivity and resulting in a slight improvement in zT.