Synthesis and low temperature transport properties of Mg2Ge1-ySby

We report on the synthesis and low temperature transport of Mg2Ge1-ySby with 0 <= y <= 0.33. In these materials Sb substitutes for Ge in the antifluorite structure. Electrical and thermal transport measurements indicate that as the Sb content increases, vacancies are formed on the Mg sites thereby contributing to variations in the transport properties. With increasing Sb content both the absolute Seebeck coefficient and electrical resistivity first decrease and then increase, while the thermal conductivity decreases monotonically. Hall measurements indicate this tendency is associated with vacancy formation at higher Sb concentrations. The lattice thermal conductivity is fitted using the Debye approximation in order to elucidate the effect of alloying. We discuss these results in terms of potential for thermoelectric applications. (C) 2007 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.