Two-Band 모델을 이용한 작은 밴드 갭을 가진 Fe(Se1-xTex)2 열전합금의 전기적 수송 특성 분석

Abstract

Environmentally sustainable thermoelectric technologies can be more broadly applied in industriesonce the performance of thermoelectric materials is improved. Several approaches have been proposed toimprove the electronic transport properties of thermoelectric materials. The effects of each approach on theelectronic properties can be evaluated by changes in the band parameters. The Single Parabolic Band (SPB)model has been widely used to determine the effect of different materials engineering strategies on bandparameters, such as the density-of-states effective mass and deformation potential. However, when thematerial has a narrow band gap, the Two-Band (TB) model better describes the changes in band parameters,as it includes the bipolar conduction from the minority carrier band. Here, the band parameters of previouslyreported Fe(Se1-xTex)2 (x = 0, 0.2, 0.6, 0.8, 1) alloys, whose band gap significantly decreases with x, have beenestimated using the SPB and TB models. While the x-dependent band parameters obtained via the SPB modelvaried abruptly with x, all the band parameters estimated by the TB model changed linearly with x. Theabruptness observed in the band parameters of the SPB model can be attributed to artifacts reflected in thesingle band, which occurs when the minority carrier band and band gap change are not included. The bipolarthermal conductivity of Fe(Se1-xTex)2 alloys was also calculated using the TB model, and is understood in termsof changes in the weighted mobility ratio, Hall carrier concentration, and band gap in terms of alloycomposition, x.