Cobalt oxide (Co ₃ O ₄ ) and Cu–doped Co ₃ O ₄ powders were synthesized via the Pechini method using cobalt acetate tetrahydrate, citric acid, and ethylene glycol as precursors, with CuF as a dopant (0, 3, 5, and 10 wt.%). After calcination at 500°C, powders were pressed into pellets and sintered at 800°C. X-ray diffraction (XRD) analysis confirmed a cubic spinel structure (ICSD No. 98-002-4210) with lattice parameters of 8.08397–8.08091 Å and crystallite sizes of 68–93 nm. Raman spectra revealed Co ²⁺ ↔O ^2- , and Co ³⁺ ↔O ^2- vibrations in tetrahedral and octahedral sites. Optical absorption analysis showed band gaps of 1.55–1.61 eV (Co ²⁺ ↔O ^2- ), and 2.37–2.43 eV (Co ³⁺ ↔O ^2- ). Electrical conductivity exhibited two regimes with activation energies of 0.366–0.570 eV (100–300°C) and 0.363–0.433 eV (300–500°C). Seebeck coefficients showed the behavior of a p-type semiconductor. The highest figure of merit (ZT = 9.76×10 ⁻³ at 500°C) was obtained for 3 wt.% Cu, indicating a ten times enhancement over pristine Co ₃ O ₄ .