Upconversion Luminescence In Nanocrystalline Y₂O₃(Er³⁺, Tm³⁺)

Y₂O₃ (Er³⁺, Tm³⁺) nanocrystals is prepared with combustion method. The effect of firing temperature, the glycine and the annealing temperature affect on the luminescence properties is studied. The phases, crystalline state and luminescence properties of the nanophosphors are studied by employing the techniques of XRD and the spectrum analyzing of the absorption, excitation and photoluminescence spectra.Firstly, the Y₂O₃ (Er³⁺) nanophosphors with the mean particle sizes in the range of 18-48 nm are prepared by combustion method with the glycine as fuel. The pure-phase Y₂O₃ (Er³⁺) nanophosphor is obtained at the annealing temperature of 1000℃.Under the excitation of 980nm laser, green emissions near 567nm and red emissions near 658nm corresponding to ⁴S_3/2→⁴I_15/2 and ⁴F_9/2→⁴I_15/2 transitions of Er³⁺ are observed. The plots of logarithm intensity of the upconvesion emissions versus logarithm pumped power of diode laser prove the green emissions and the red emissions are both two-double-photon process. The ratio of the red emission to the green emission increases obviously with the increasing of Er³⁺ concentration. The energy transfer between Yb³⁺ and Er³⁺ will increase the red emission greatly after the Yb³⁺ is doped.The luminescence mechanism of Y₂O₃ (Tm³⁺, Yb³⁺) is also studied. When Yb³⁺ is doped, It is found that the blue emissions near 482nm corresponding to ¹G₄→¹H₆ transition and the emissions near 794nm corresponding to ³H₄→³H₆ are three-photon process and double-photon process respectively. Furthermore, the 794nm emissions weaken the blue emissions.Yb³⁺ leads to the direct up-conversion sensitization between Yb³⁺ and Tm³⁺.