Effect of Ta Doping on the Microstructure and Thermoelectric Properties of Bi2O2Se

In this study, Bi2-xTaxO2Se (x = 0, 0.02, 0.04, 0.06, and 0.08) ceramics were prepared using a synthesis method combining high-energy ball milling and cold pressing. Furthermore, the effects of tantalum (Ta) doping on the microstructure and thermoelectric properties of Bi2O2Se were systematically investigated. The results indicate that Ta doping effectively improves the carrier concentration and mobility, thus increasing the electrical conductivity from 8.75 S cm(-1) to 39.03 S cm(-1) at 323 K. Consequently, the power factor is improved, reaching a maximum value of 124 mu W m(-1) K-2 for the Bi1.92Ta0.08O2Se sample at 773 K. Moreover, the thermal conductivity of Bi1.96Ta0.04O2Se is reduced to 0.50 Wm(-1) K-1. Finally, the maximum dimensionless figure of merit (ZT) value of the Bi1.94Ta0.06O2Se sample reached 0.18, which was 64% higher than that of Bi2O2Se (0.11). These results indicate that Ta doping and high-energy ball milling can optimize the electrical and thermal properties and thus improve the thermoelectric properties of ceramics.