Highly enhanced stability and thermoelectric performance of copper sulfides-based composites by multiphase engineering

Abstract

Interfaces play a key role in affecting carrier, ion and phonon migration, and constructing appropriate phase interfaces allows for synergistically improving the related physical performance. Herein, the effects of various interfaces on electronic and thermal transport in copper sulfide are studied. Dramatically improved mechanical properties and service stability in copper sulfide-based composites are realized while excellent thermoelectric performance is maintained by employing multiphase engineering. The phase composition and intrinsically excessive hole concentration of copper sulfide have been elaborately tailored by regulating Cu vacancies after compositing insulated boron, leading to a significantly optimized Seebeck coefficient. The enhanced phonon scattering effect by high-density interfaces and the deteriorated electrical conductivity contribution result in the overall reduced thermal conductivity. A peak ZT of 1.32 at 773 K could be achieved in the Cu1.8S-0.75 wt% B bulk specimen. In addition, multiscale boron inclusions favor improving mechanical strength by dispersing strengthening. More importantly, spontaneously generated nanoprecipitates inhibit further sulfur volatilization in the matrix, and the introduced interfaces are beneficial for suppressing Cu ion long-range migration as well, which improves the service stability of copper sulfide-based bulk composites. Broadly, the strategy of constructing multiphase by compositing insulated particles paves an important way toward reasonable design of excellent TE materials.