Enhanced thermoelectric composite performance from graphene nanosheets additives in AgSbTe2 matrix

Abstract

The glass-like thermoelectric material AgSbTe2 has shown great potential in recent years due to its inherent low thermal conductivity and large Seebeck coefficient. Using nanostructured engineering to improve the electrical properties of AgSbTe2 while reducing its lattice thermal conductivity, is the main focus of thermoelectric performance optimization. Herein, we report a significant improvement in the thermoelectric performance of a composite prepared by incorporation of graphene nanosheets into surface-modified AgSbTe2 matrix via the hetero-aggregation method. Compared with the matrix, all composite bulk samples exhibited lower lattice thermal conductivity due to the enhanced phonon scattering at the new formed interfaces. Besides, the formation of the conductive network structure by graphene nanosheets in the matrix greatly increased the conductivity of AgSbTe2 from 1.6 to 2.5*104 S/m without significant deterioration of the Seebeck coefficient. Consequently, the maximum ZT of about 1.25 was obtained at 500K for 0.9 vol% graphene/AgSbTe2, which was 69% higher than that of pristine AgSbTe2 bulk. This also validates that the hetero-aggregation composite method is a promising processing scheme for designing novel two-dimensional thermoelectric nanocomposites.