Structure-Property Tuning in ZnO Aerogels: Optical and Photoluminescence Modulation by Low-Level Yttrium Doping

Yttrium-doped ZnO aerogel nanostructures with low Y concentrations (0.5 and 1 at.%) were synthesized through a modified sol–gel process coupled with supercritical isopropanol drying, yielding highly porous and crystalline materials. Structural and optical characteristics were investigated using X-ray diffraction (XRD), Fourier-transform infrared spectroscopy (FTIR), Utraviolet–Visible (UV–Vis) spectroscopy, and photoluminescence (PL) spectroscopy. XRD results confirmed the formation of single-phase polycrystalline ZnO with a hexagonal wurtzite structure for all samples, along with lattice perturbations consistent with the substitution of Zn2+ by Y3+ ions. FTIR spectra further supported successful ZnO network formation, revealing a systematic shift of the Zn–O stretching band toward lower wavenumbers upon Y incorporation. UV–Vis measurements showed that yttrium doping enhances optical absorbance and induces a slight redshift of the absorption edge, indicating a modest narrowing of the band gap. PL analysis demonstrated a remarkable enhancement in UV and visible emission for the ZnO:Y (0.5 at.%) sample, which exhibited the highest overall PL intensity across the investigated spectral range. This enhancement is attributed to an increased radiative recombination rate of photogenerated carriers and the formation of additional defect-related states introduced by low-level Y doping. These findings highlight the strong potential of yttrium-modified ZnO aerogels for tunable optical and photonic applications.