Phase stability and thermoelectric properties of Cu_10.5Zn_1.5Sb₄S₁₃ tetrahedrite

Cu_10.5Zn_1.5Sb₄S₁₃ tetrahedrite compound was prepared by mechanical milling of Cu₂S, ZnS and Sb₂S₃ powders and spark plasma sintered (SPS) to dense samples. The phase formation, chemical homogeneity, thermal stability of the compound and the thermoelectric properties of the sintered samples were evaluated. Single phase tetrahedrite with the crystallite size of 40 nm was obtained after 30 h of milling followed by annealing at 573 K for 6 h in an argon atmosphere. In-situ high-temperature X-ray diffraction studies revealed that the phase is stable up to 773 K. The Seebeck coefficient of the sintered samples of density >98% shows p-type behavior with maximum thermopower of 170 μV/K at 573 K. The electrical resistivity (ρ) decreases with temperature up to 475 K and then increases. A low thermal conductivity of 0.5 W/(m⋅K), in combination with moderate power factor gave a maximum ZT of ∼0.038 at 573 K in Cu_10.5Zn_1.5Sb₄S₁₃ sample having a grain size of ∼200 nm. - Highlights: • Simple, scalable nanocrystalline tetrahedrite synthesis method demonstrated. • Thermal stability of tetrahedrite critical for a thermoelectric use is studied. • Processing issues and their effects on thermoelectric properties were addressed.