Structural and thermoelectric properties of sintered silicon clathrates: Ba6Eu2Ga16Si30 nominal composition

We have prepared Ba8−xEuxGa16Si30 clathrate system by spark plasma sintering method at different temperatures 1093-1273 K using a starting material with Ga rich composition Ba6Eu2Ga17Si29. Powder x-ray diffraction (XRD), Rietveld structure refinement, FE-SEM and EPMA indicate that the Ga composition slightly increases with a decrease in sintering temperature, leading to a decrease in the carrier concentration. The Seebeck coefficient, the electrical conductivity, and the thermal conductivity vary with the sintering temperature according to the change in the carrier concentration. The thermoelectric figure of merit at 900 K increases from 0.28 to 0.35 by decreasing the sintering temperature from 1273 K to 1093 K.