Sonochemical Synthesis and Structural–Thermal Characterization of CdO–ZnO Mixed Oxide Nanoparticles: XRD and Williamson–Hall Analysis

This study presents the ultrasonic-assisted sonochemical synthesis and comprehensive characterization of (CdO)₁₋ₓ(ZnO)ₓ mixed oxide nanoparticles (MONPs) using X-ray diffraction (XRD), Williamson-Hall (W-H) analysis, and thermogravimetric analysis (TGA). XRD patterns reveal distinct crystallographic phases, with CdO exhibiting cubic structure (Fm-3m) via prominent (110), (111), (200), (220), (152), (311), and (222) reflections, while ZnO adopts a hexagonal wurtzite structure (P6₃mc) with (100), (002), (101), (102), (110), (103), (112), and (202) planes. A secondary phase (*) confirms CdO-ZnO solid solution formation. Vegard’s law governs the composition-dependent lattice parameter variation, where pure CdO (a ≈ 4.695 Å) and ZnO (a ≈ 3.249 Å, c ≈ 5.206 Å) exhibit predictable shifts in MONPs (e.g., Cd₀.₅Zn₀.₅O yields a ≈ 4.5 Å for cubic or expanded hexagonal parameters). Williamson-Hall analysis quantifies strain and crystallite size effects, demonstrating increased tetrahedral (LA) and octahedral (LB) site distances with rising lattice constant due to atomic size disparity. TGA profiles indicate a two-stage decomposition: an initial 1.8% mass loss (370°C, moisture/solvent removal) followed by a major 51% loss (408°C, organic precursor degradation), culminating in 47.2% residual mass at 800°C, affirming high thermal stability. These findings underscore the structural integrity and tunable properties of CdO-ZnO MONPs, positioning them as robust candidates for high-temperature applications, including photocatalysis, gas sensing, and optoelectronic devices.