Crystal Structure and Photoluminescence Properties of Eu-Doped Y₂O₃ Nanoparticles Prepared by Mechanical Milling

Abstract

We have used a top-down approach of the mechanical milling to fabricate Y₂O₃:Eu³⁺ nanoparticles (NPs), and then studied their crystal structure and photoluminescence (PL) properties based on X-ray diffraction (XRD), electron paramagnetic resonance (EPR) and PL spectroscopy. XRD results revealed that the change of the milling time (t_m) from 0 to 540 minutes (min) decreased the average crystallite size (d) of NPs from ∼83 nm (for t_m = 0 min) to below 3.5 nm (for t_m = 540 min). This varied lattice strain and defects, and caused the structural changes, which influenced directly the PL properties of NPs. Among the fabricated NP samples, those with t_m = 5–10 min (corresponding to d ≈ 25–40 nm) offer strongest PL intensity at ∼611 nm (due to the electronic transition ⁵D₀ → ⁷F₂). The increase of the longer milling time (i.e., lowering d) reduces quickly the intensity of this emission, but slightly increased the intensity of auxiliary emissions. The nature of the observed phenomena was discussed.