General Nonaqueous Sol−Gel Synthesis of Nanostructured Sm₂O₃, Gd₂O₃, Dy₂O₃, and Gd₂O₃:Eu³⁺ Phosphor

Abstract

In this paper, we report on the synthesis of nanostructured rare earth oxides (Sm₂O₃, Gd₂O₃, Dy₂O₃) via a facile benzyl alcohol based nonaqueous sol−gel process followed by calcination at moderate temperature. During the synthesis, rare earth acetylacetonates were used as the precursors. The resulting samples were characterized by X-ray powder diffraction, scanning electron microscopy, transmission electron microscopy, high-resolution transmission electron microscopy, and photoluminescent spectroscopy. The final nanostructured RE₂O₃ products were observed to possess two typical shapes: stacks of ultrathin nanodisks for Sm₂O₃ and hierarchical nanosheet microspheres for Gd₂O₃ and Dy₂O₃, respectively. This method could be extended to prepare high-quality luminescent Gd₂O₃:Eu³⁺ flowerlike superstructures with a strong red emission corresponding to ⁵D₀ → ⁷F₂ transition (612 nm) of Eu³⁺ under ultraviolet excitation (260 nm). The possible formation mechanisms of the ultrathin nanodisk stacks and hierarchical nanosheet microspheres are proposed on the basis of the characterization results. This study provides an alternative nonaqueous approach for the synthesis of nanostructured rare earth oxides.