Abstract: Y2O3∶Er3+ ，Yb3+ nanocrystals were synthesized at different
pH values and various urea concentration by homogeneous coprecipitation method after 700 ℃ sintering. The phase structure, microstructure and luminescent properties of the samples were characterized by Xray diffraction (XRD), transmission electron microscopy (TEM), Fourier transform infrared spectra (FTIR) and fluorescence spectrometer. The results show that the pH value has great effect on the particle size of Y₂O₃∶Er³⁺,Yb³⁺ and the particle size increases with the increase of pH value. The upconversion fluorescence intensity of green (500—600 nm) and red (650—700 nm) is obviously enhanced, and redgreen ratio is gradually reduced. The effect of urea concentration on Y₂O₃∶Er³⁺,Yb³⁺ nanoparticles is small.

Key words: upconversion luminescence, rare earth ion, coprecipitation method