Thermoelectric properties and nonstoichiometry of GaGeTe

Polycrystalline samples of composition Ga1+xGe1−xTe (x=−0.03÷0.07) and GaGeTe1−y (y=−0.02÷0.02) were synthesized from elements of 5 N purity using a solid state reaction. The products of synthesis were identified by X-ray diffraction; phase purity and microstructure were examined by EDX/SEM. Samples for measurement of transport properties were prepared using hot-pressing. They were characterized by measurement of electrical conductivity, the Hall coefficient, and the Seebeck coefficient over a temperature range 80–480 K and of thermal conductivity over a temperature range 300–580 K. All samples show p-type conductivity. We discuss the influence of stoichiometry on the phase purity of the samples and on free carrier concentration. The investigation of thermoelectric properties shows that the power factor of these samples is low compared to state-of-the-art materials at room temperature but increases distinctly with temperature.