Investigation of electrical resistivity and phase stability in superionic Cu₂Se nanocomposite reinforced with well-distributed Cu₅Zn₈ CMA nanoparticles

In this study, the electrical resistivity behavior and phase evolution of Cu₂Se–1 wt% Cu₅Zn₈ nanocomposite were systematically investigated as a function of milling time. Cu₂Se-based nanocomposite powders were synthesized using mechanical alloying and consolidated by spark plasma sintering (SPS). X-ray diffraction (XRD), field emission scanning electron microscopy (FESEM), and energy-dispersive X-ray spectroscopy (EDS) analyses revealed that increasing milling time led to crystallite size reduction (from ~19 to ~6 nm), increased lattice strain, and a gradual transformation from β-Cu₂Se to α-Cu₂Se. The electrical resistivity was measured between 300 and 550 K. The sample milled for 5 h exhibited the lowest electrical resistivity, attributed to the dominance of β-Cu₂Se phase, uniform Cu₅Zn₈ nanoparticle dispersion, and higher carrier mobility. Prolonged milling (15–20 h) increased resistivity due to enhanced defect density, copper depletion, and inhomogeneous secondary phase distribution. These findings demonstrate that optimizing the balance between microstructural refinement and β-phase stability is crucial for improving the electrical transport and thermoelectric potential of Cu₂Se-based nanocomposites.