Preparation, characterization, and strong upconversion of monodisperse Y2O3:Er3+,Yb3+ microspheres

Monodisperse Y2O3:Er and Y2O3:Er,Yb microspheres with diameter of 1.5–3 μm, which are composed of nanoparticles with size of about 50 nm, were prepared by a simple solvothermal method followed by further heat treatment. The structural properties of samples were investigated by X-ray diffraction; field emission scanning electron microscopy, Raman spectroscopy and Fourier transform infrared spectroscopy. Especially, the effect of CH3COONa on the formation of microspheres was investigated. Under 980 nm laser excitation, strong green (518–570 nm), strong red (645–686 nm) and weak violet (405–420 nm) upconversion emissions have been observed in Y2O3:Er and Y2O3:Er,Yb microspheres. The upconversion mechanisms were studied through laser power and concentration dependence of the upconverted emissions. The upconversion properties indicate that Y2O3:Er and Y2O3:Er,Yb microspheres may be used in upconversion phosphors.