S0.05Co4Sb11.6Te0.4 skutterudite introduced into graphene at high pressure and high temperature and its thermoelectric performance enhancement

Abstract

A series of graphene-S0.05Co4Sb11.6Te0.4 (Cx-S0.05Co4Sb11.6Te0.4) composite polycrystalline skutterudite materials with graphene stoichiometric ratio of x = 0, 0.05, 0.10, 0.20 have been successfully prepared by high pressure and high temperature (HPHT) technology. Graphene is a two-dimensional material with large carrier mobility and large specific surface area. Through microscopic observation, it is found that graphene is attached to the grains in the sample. At the same time, with the increase of graphene content, grain growth is inhibited. Graphene addition reduces the thermal conductivity of skutterudite by increasing grain boundaries and achieves the purpose of optimizing its thermoelectric properties. At the same time, there are numerous lattice defects and distortions introduced in skutterudite synthesized by HPHT technology. Finally, the samples were synthesized under the conditions of 1.5 GPa and 900 K. The lattice thermal conductivity of the graphene composite sample Cx-S0.05Co4Sb11.6Te0.4 with x = 0.10 reaches a minimum of 0.99 at 773 K, and the zT value of this sample is 1.25 at 773 K, which is greater than pure S0.05Co4Sb11.6Te0.4, its zT value is 1.00 at 773 K. Compared with the method of synthesizing skutterudite under normal pressure, the HPHT technology can dramatically reduce the reaction time from several days to less than 30 min, while forming a high-pressure airtight reaction environment, which can effectively prevent the volatilization and oxidation of samples during the reaction process, thus providing a convenient method for synthesizing thermoelectric materials quickly and efficiently.