Microwave solvothermal synthesis of Eu³⁺-doped (Y,Gd)₂O₃ microsheets

A microwave-assisted solvothermal process was employed to synthesize the sheet-like (Y,Gd)-oxalate precursors. (Y,Gd)₂O₃ was obtained by thermal decomposition of the precursors above 550°C. The samples were analyzed by X-ray diffraction (XRD), Fourier-transform infrared spectrometry (FT-IR), scanning electron microscopy (SEM), thermogravimetric/differential scanning calorimeters (TG/DSC), and transmission electron microscopy (TEM). It was found that the sheet-like (Y,Gd)-oxalate precursors (indicated as (Y,Gd)₂(C₂O₄)₃ nH₂O) were sensitive to the synthetic conditions such as microwave irradiation power and volume ratio of ethylene glycol (EG) to water (defined as R). When R=1, the products presented sheet-like morphology, and higher R value could change the aspect ratio of precursor to micro/nano rod-like. The possible growth process was also proposed based on the results. The excitation spectrum of the (Y,Gd)₂O₃:Eu³⁺ (5mol% of Eu³⁺) microsheets was observed with a maximum peak at 238nm (λem=611nm). The emission spectrum was recorded under excitation wavelength of 238nm and exhibited the strongest peak at 611nm. In addition, (Y,Gd)₂O₃:Eu³⁺ with sheet-like shape had the strongest emission peaks.