Impact of Structural Changes on Energy Transfer in the Anion-Engineered Re3+:Y2O3 Through Low-Temperature Synthesis Approach

Abstract

Anion engineering has proven to be an effective strategy to tailor the physical and chemical properties of metal oxides by modifying their existing crystal structures. In this work, a low-temperature synthesis for rare earth (RE)-doped Y₂O₂SO₄ and Y₂O₂S was developed via annealing of Y(OH)₃ intermediates in the presence of elemental sulfur in a sealed tube, followed by a controlled reduction step. The crystal structure patterns (X-ray diffraction) and optical spectra (UV-IR) of Y₂O₂SO₄, Y₂O₂S, and crystalline Y₂O₃ were collected throughout the treatment steps to correlate the structural transformations (via thermogravimetric analysis) with the optical properties. Local and long-range crystallinities were characterized by using X-ray and optical spectroscopy approaches. Systematic shifts in the Eu³⁺ excitation and emission peaks were observed as a function of SO₄^2- and S^2- concentrations resulting from a crystal evolution from cubic (Y₂O₃) to trigonal (Y₂O₂S) and monoclinic (Y₂O₂SO₄), which can modify the local hybridization of sensitizer dopants (i.e., Ce³⁺). Ultimately, Tb³⁺ and Tb³⁺/Ce³⁺ doping was employed in these hosts (Y₂O₂SO_4, Y₂O₂S, and Y₂O₃) to understand energy transfer between sensitizer and activator ions, which showed significant enhancement for the monoclinic sulfate structure.