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+ (5 mol% of Eu3+) microsheets was observed with a maximum peak at 238 nm (λem = 611 nm). The emission spectrum was recorded under excitation wavelength of 238 nm and exhibited the strongest peak at 611 nm. In addition, (Y,Gd)2O3:Eu3+ with sheet-like shape had the strongest emission peaks.