Impact of Structural Changes on Energy Transfer in the Anion-Engineered Re 3+ :Y 2 O 3 Through Low-Temperature Synthesis Approach.

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 Y 2 O 2 SO 4 and Y 2 O 2 S 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 Y 2 O 2 SO 4 , Y 2 O 2 S, and crystalline Y 2 O 3 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 Eu 3+ excitation and emission peaks were observed as a function of SO 4 2- and S 2- concentrations resulting from a crystal evolution from cubic (Y 2 O 3 ) to trigonal (Y 2 O 2 S) and monoclinic (Y 2 O 2 SO 4 ), which can modify the local hybridization of sensitizer dopants (i.e., Ce 3+ ). Ultimately, Tb 3+ and Tb 3+ /Ce 3+ doping was employed in these hosts (Y 2 O 2 SO 4, Y 2 O 2 S, and Y 2 O 3 ) to understand energy transfer between sensitizer and activator ions, which showed significant enhancement for the monoclinic sulfate structure.