Enhanced thermoelectric properties of polycrystalline BiCuSeO via dual-doping in Bi sites

摘要

The effect of Pb and La substitution on the thermoelectric properties of BiCuSeO oxyselenide has been studied. It is revealed that Pb doping can significantly improve the electrical conductivity due to the increased carrier concentration, which results in a large power factor in the range of 700 to 800 mu W m(-1) K-2 at 873 K. In particular, the electrical transport properties can be further improved obviously over the entire measured temperature range after replacing some Bi3+ ions with La3+ ions in Bi0.94Pb0.06CuSeO. The electrical conductivity has increased from 408 S cm(-1) for Bi0.94Pb0.06CuSeO to 594 S cm-1 for Bi0.93Pb0.06La0.01CuSeO at 327 K due to the increased carrier mobility. Combining with the moderate Seebeck coefficient which is over 124 mu V K-1, the power factor has been significantly improved. An optimal value of 1059 mu W m-1 K-2 at around room temperature is achieved for Bi0.93Pb0.06La0.01CuSeO and is much higher than most reported values. Additionally, the increased total thermal conductivity for the Pb-doped sample compared with the pristine sample has been suppressed after further doping the La element in Bi0.94Pb0.06CuSeO. Therefore, a maximum ZT value of nearly 0.90 at 873 K for the sample Bi0.92La0.02Pb0.06CuSeO has been finally obtained, which is similar to 36% and similar to 16% higher as compared with those of the La-free sample Bi0.94Pb0.06CuSeO and the reported Pb-free sample Bi0.92La0.08CuSeO.