Bi2Te3의 열전특성에 미치는 Al2O3 분산입자의 영향

Abstract

In this research, we studied the effects of particle size on the thermoelectric properties of Bi2Te3. Al2O3 powders of two different particles sizes (50 nm, 250 nm) were mixed with Bi2Te3 powder by planetary ball milling to form two mixtures, and then each mixture was sintered using the spark plasma method. Phase structure and grain size were then analyzed by X-ray diffractometry (XRD) and field-emission scanning emission microscopy (FE-SEM), respectively. Their thermoelectric properties were then evaluated by measuring their Seebeck coefficient, electric resistivity, and thermal conductivity. Grain size, density, carrier concentration, and mobility of Bi2Te3 had all decreased owing to the addition of Al2O3 particles. However, a smaller particle size (50 nm) had greater influence on carrier concentration reduction, while a larger particle size (250 nm) had greater influence on the reduction in mobility. These results may have been caused by different changes in the energy barrier width induced by the varying particle size. The Seebeck coefficient increased regardless of particle size of added Al2O3. Electrical resistivity of sintered bodies decreased with decreasing particle size, and followed the same trends as carrier concentration variation with particle size. Thermal conductivity too decreased; however, the amount of decrement became lower with larger particle size. The highest figure of merit obtained was 0.9 at 25℃ for the Bi2Te3/Al2O3 (250 nm) sample. The result followed electrical properties variation then reduced thermal conductivity.