Bi 도핑에 따른 SnTe의 상온 최대 열전성능지수 예측

Abstract

SnTe has drawn much attention due to its Pb-free composition along with tunable electronic andlattice structures. However, its intrinsically high defect concentration and high lattice thermal conductivity(κl) have hindered its application in devices. Recently, Bi doping at Sn-sites in Sn1-xBixTe (x = 0.0 – 0.08) hasbeen demonstrated to be effective in improving the thermoelectric performance (zT) of SnTe. Bi doping wasparticularly effective in improving the Seebeck coefficient in a wide range of temperature while suppressingits κl. However, the effect of Bi doping on electronic band structure of SnTe has not been studied. Here, weapplied the Single Parabolic Band (SPB) model to the room temperature electronic transport propertiesmeasurements (Seebeck coefficient, electrical conductivity, Hall carrier concentration) and analyzed howelectronic band parameters like the density-of-states effective mass (md*), non-degenerate mobility (μ0),weighted mobility (μw), and B-factor changes with a changing Bi doping content (x). As the x increases, themd* increases while μ0 decreases. As the μw depends both on md* and μ0, it peaks at x = 0.02. Lastly, the Bfactoris related to the ratio of μw to κl, due to significantly decreasing κl at high x, the B-factor also becomesthe highest at x = 0.08. Based on the B-factor of x = 0.08 sample, the highest theoretical zT of 0.31 is predictedusing the SPB model. This is approximately 2.2 times higher than the experimental zT (~0.139) reported inliterature at 300 K. The SPB model also guides us that the highest theoretical zT of 0.31 can be achievedif its Hall carrier concentration is tuned to 9.06 × 1018 cm-3.