First-principles simulation on thermoelectric properties in Bi-Sb System

Abstract

Abstract. Thermoelectric properties of bismuth-antimony (Bi-Sb) alloy system were simulated on the basis of first-principles calculation, to discuss the potential for thermoelectric devices. Atomistic model structures of Bi-Sb alloy system were devised in the forms of single-crystal bulk and one-dimensional nanowire under the periodic boundary condition. The cell parameters of the bulk model were simulated with respect to temperature by the quasiharmonic approximation through phonon calculation, and dependences of the Seebeck coefficient on composition, surface condition, and temperature have been demonstrated by using our original methodology in terms of the electronic state of Bi-Sb alloy system. For the single-crystal bulk Bi-Sb models, a meaningful effect of the composition on the Seebeck coefficient has not been observed, whereas a clear difference in phonon dispersion was confirmed between pure Bi and Sb-substituted Bi, leading to the significant difference in thermal conductivity. We clarified that the surface condition is a key point to control the Seebeck coefficient for the nanowire form. IntroductionApplication of thermoelectric devices is spreading over a variety of special environments and conditions in power generation and refrigeration. For the low-temperature environment, bismuthantimony (Bi-Sb) alloy is one of the most promising thermoelectric materials with highly efficient energy conversion in the temperature range less than 200 K [1][2][3][4][5][6][7]. Generally, the thermoelectric performance of materials is evaluated by the dimensionless figure of merit, ZT = (S 2 s/k)T, where S is the Seebeck coefficient, s is the electric conductivity, and k is the thermal conductivity [8]. Even at low temperature T, the dimensionless ZT for some appropriate Bi-Sb alloy systems comes up to an efficient value; for example, ZT = 0.6 has been reported for the single-crystal Bi1-xSbx alloy with the compositions of Bi0. 91Sb0.09 and Bi0. 85Sb0.15 [1]. In addition, the development of Bi-Sb alloy-based composite materials have been an important target to add a merit of mechanical point to the unique thermoelectric performance at low temperature. We have succeeded in fabricating a novel composite material based on Bi0. 85Sb0.15 and graphene with good thermoelectric performance [2].To enhance energy conversion efficiency, it is well known that the miniaturization of thermoelectric materials to low dimension at nanoscale is effective technique [3,[9][10][11][12][13]. Rabina et al. has simulated ZT of Bi1-xSbx nanowire numerically based on the conventional procedures [3]. We have

2D V‐V Binary Materials: Status and Challenges

“…Different engineering approaches are implemented to improve the ZT value of various materials including V‐V binary crystals. First‐principles simulations have indicated that the composition of bulk Bi 1− x Sb x has no effect on the ZT value . Te doping can enhance the ZT value of bulk Bi 1− x Sb x by one order of magnitude .…”