Effect of Cu Doping on the Structural, Vibrational, Thermal, and Densification Properties of Sol–Gel Derived ZnO Nanoceramics

Pure and Cu-doped ZnO nanoceramic pellets containing 0, 2, 4, and 6 wt.% Cu were successfully synthesized via the sol–gel method, compacted into pellets, and sintered at 1000 °C. The influence of Cu incorporation on the structural, vibrational, thermal, densification, and chemical stability properties of ZnO nanoceramics was systematically investigated using X-ray diffraction (XRD), Fourier-transform infrared spectroscopy (FTIR), Raman spectroscopy, density and porosity measurements, thermogravimetric analysis (TGA), derivative thermogravimetry (DTG), differential scanning calorimetry (DSC), and inductively coupled plasma optical emission spectroscopy (ICP–OES). XRD analysis confirmed the formation of a single-phase hexagonal wurtzite ZnO structure (JCPDS No. 36-1451) without detectable secondary phases. The crystallite size decreased from 35.1 nm for ZnCu0 to 26.4 nm for ZnCu6, while the lattice parameters decreased from a = 3.249 Å and c = 5.206 Å to a = 3.239 Å and c = 5.194 Å, respectively. The microstrain increased from 3.31 × 10⁻³ to 4.42 × 10⁻³, and the dislocation density increased from 0.81 × 10¹⁵ m⁻² to 1.43 × 10¹⁵ m⁻², indicating enhanced lattice distortion with Cu incorporation. FTIR and Raman analyses confirmed successful Cu substitution through systematic shifts in the Zn–O vibrational bands and increased defect-related Raman modes. The bulk density increased from 4.82 to 5.31 g cm⁻³, while the apparent porosity decreased from 18.6% to 9.4%. The total weight loss obtained from TGA decreased from 11.5% for ZnCu0 to 9.2% for ZnCu6, demonstrating improved thermal stability. Furthermore, the released ion concentration decreased from 0.0085 ppm to 0.0027 ppm, indicating enhanced chemical durability. Among all compositions, ZnCu6 exhibited the highest densification, thermal stability, and chemical resistance. These findings demonstrate that Cu doping effectively tailors the structural and functional properties of ZnO nanoceramics, making them promising candidates for advanced ceramic and functional-material applications