Thermoelectric characterization of the clathrate-I solid solution Ba8−δAuxGe46−x

Abstract

Clathrate-I-based materials are promising for waste-heat recovering applications via thermoelectric (TE) effects. However, the lack of highly efficient p-type materials hampers the development of clathrate-based TE devices. In this work, the synthesis of the p-type semiconductor Ba7.8Au5.33Ge40.67 with clathrate-I structure is up-scaled by steel-quenching and spark plasma sintering treatment at 1073 K. A thermoelectric figure of merit ZT ≈ 0.9 at 670 K is reproducibly obtained, and 40 chemically homogeneous module legs of 5 × 5 × 7 mm3 are fabricated. By using a carbon layer as a diffusion barrier, electrical contacts are sustainable at elevated application temperatures. Eight couples with the clathrate-I compounds Ba7.8Au5.33Ge40.67 as p-type and Ba8Ga16Ge30 as n-type materials are integrated into a TE module with an output power of 0.2 W achieved under a temperature difference ΔT = 380 K (T1 = 673 K and T2 = 293 K). The thermoelectric performance of Ba7.8Au5.33Ge40.67 demonstrates the potential of type-I clathrates for waste heat recycling.