Defect-engineered structural and optical properties of mechanochemically activated BaZrO 3 /Y 2 O 3 /SrTiO 3 hybrid oxide nanoparticles

In this research, high-energy ball milling was employed in order to investigate the influence of mechanochemically induced defect engineering on the structural, surface and optical properties of BaZrO 3 -based perovskite oxides. Two compositions were investigated with fixed Y 2 O 3 content and variable SrTiO 3 . Scanning electron microscopy analysis revealed nanoparticles with median particle sizes below 120 nm, assembled into hierarchical defect-rich agglomerates exhibiting pronounced interparticle necking and mechanically activated interfaces. X-ray diffraction confirmed preservation of the cubic BaZrO 3 structure without detectable secondary crystalline phases, while the observed lattice parameter variations are consistent with partial substitution of Ba 2+ and Zr 4+ sites by Sr 2+ , Ti 4+ and Y 3+ species. X-ray photoelectron spectroscopy revealed enhanced defect-associated oxygen contributions, indicating substantial oxygen-vacancy formation and local lattice distortion. Optical characterization demonstrated a significant reduction of the optical band gap from 4.94 eV for BaZrO 3 to 3.45 and 3.39 eV for the modified compositions. Simultaneously, excitation and emission spectra exhibited pronounced red-shifts together with broad visible photoluminescence bands centered at 448 and 454 nm, associated with the incorporation of Y 2 O 3 . The observed optical behavior was attributed to oxygen-vacancy-mediated electronic states and defect-assisted radiative recombination pathways generated during mechanochemical processing. These results demonstrate that high-energy ball milling provides an effective route for tailoring the electronic structure and optical response of BaZrO 3 -based hybrid oxide nanoparticles for optoelectronic applications.