Synthesis and thermoelectric properties of p-type Ba₈Au_xSi_46-xclathrate

Abstract

View the article online for updates and enhancements. clathrates were synthesized by the arc melting method and a subsequent annealing treatment. The as-synthesized sample contained some precipitates rich in Au at the grain boundaries, and the precipitates were reduced by annealing at 1000 ˚C. The Au content of the clathrate phase for the as-synthesized sample, Ba 7.4 Au 4.7 Si 41.3 , was slightly lower than that for the stoichiometric composition, Ba 8 Au 6 Si 40 . In the annealed samples, the Au content of the clathrate phase increased with annealing time. These results indicated that Au can diffuse from Au-rich precipitates to the clathrate phase by annealing. The Seebeck coefficient of the as-synthesized and 1 hour annealed sample, Ba 7.5 Au 5.7 Si 40.3 , were -80 and +100 V/K at 500 ˚C, respectively. This suggested that the carrier type was changed by the Au content in the clathrate. In the samples annealed for longer than 1 hour, the Seebeck coefficient decreased with annealing time. This indicated that the hole carrier concentration increased in excess because of overdoping due to the diffusion of Au. Related content