Ball Milling and Post Annealing as an Effective Route to Synthesize Co1-xCuxSbS Paracostibite Thermoelectric Material

Metal sul􀀎des containing non-toxic and earth-abundant elements have emerged as new environmentally friendly thermoelectric materials. In the present work, a new, fast and large scale route to synthesize bulk nanostructured Co1-xCuxSbS paracostibite is presented. Stoichiometric compositions of Co1-xCuxSbS nanoparticles with 0 ≤ x ≤ 0.08 were 􀀎rst processed by high energy ball milling for 3 h and then annealed at different temperatures between 400 ºC to 650 ºC for 1 h. The phase transformations and diffusion process during annealing were thoroughly studied by X-ray diffraction (XRD) and scanning electron microscopy (SEM). Agglomerated nanoparticles with sizes in the range from 40 nm to 80 nm were obtained after 3 h of ball milling and remained below 100 nm after annealing and hot pressing. The thermoelectric properties of hot-pressed samples, including the Seebeck coef􀀎cient (S), electrical conductivity (􀀁) and thermal conductivity (􀀃), were measured from room temperature up to 723 K. All the samples exhibited a p-type semiconductor character at room temperature and underwent a transition from p-type to n-type conduction above 473 K. Maximum ZT value of 0.12 was obtained for Co0.06Cu0.04SbS4 at 723 K.