Ultrasonic Spray Pyrolysis Synthesis of a Shell-like Porous Zinc Oxide/Copper Oxide Nanomaterial at 400 °C: XRD Line-Broadening Analysis and SEM/EDS Characterization

A porous zinc oxide/copper oxide nanomaterial was synthesized by ultrasonic spray pyrolysis at 400 °C from an aqueous 90:10 Zn:Cu cation feed, using a 1.7 MHz atomizer and argon without added hydrogen. X-ray diffraction confirms dominant wurtzite ZnO; weaker features are compatible with candidate Cu2O and CuO contributions, but the copper-containing phases are not unambiguously resolved. Reliable phase fractions and the Zn:Cu ratio in the collected powder are not established. Reflection-mode Scherrer estimates give a mean ZnO coherent-domain size of 17.1 nm after correction with an instrumental FWHM of 0.08° obtained from a silicon standard. Previously processed transmission-mode fits give apparent sizes of 22.0–27.1 nm, with the FWHM-based Halder–Wagner representation showing the strongest linearity (R2 = 0.9460). The model comparison remains exploratory because individual transmission widths are not tabulated and the W–H fits have weak linearity. The 500 and 600 °C profiles retain the principal ZnO reflections and support a qualitative temperature comparison. SEM reveals porous, agglomerated, partially hollow secondary structures, and EDS confirms Zn, O, and Cu without establishing a quantitative Zn:Cu ratio. A proposed droplet-to-particle mechanism describes possible routes to local phase contact. Surface copper speciation, nanoscale contact, and an electronic heterojunction remain unverified.