Upconversion White Light Output in (Y0.9Gd0.1)2O2S Matrix Tri-Doped with Yb3+/Tm3+/Er3+ or Yb3+/Tm3+/Ho3+

(Y0.9Gd0.1)(2)O2S:0.08Yb/Tm/Er and (Y0.9Gd0.1)(2)O2S:0.08Yb/Tm/Ho powders doped with different concentrations of active ions were prepared by a traditional flux method. The phase composition, the crystal structure, the particle morphology, the light absorption property, upconversion luminescent property, and upconversion emission color were investigated by XRD, SEM, R%, UPL and CIE, respectively. All tri-doped samples doped with different amounts of active ions were presented a single hexagonal oxysulfide phase. The particles were polyhedron in shape and approximately 1 similar to 4 mu m in particle size. Tm3+ acted as the sensitization agent to increase the green emission intensity of Er3+ and the red emission intensity of Ho3+ by an energy transfer process. White upconversion luminescence was successfully outputted with the color coordinate being (0.2977, 0.3296) for (Y0.9Gd0.1)(2)O2S:0.08Yb/0.01Tm/0.01Er and (0.3249, 0.3571) for (Y0.9Gd0.1)(2)O2S:0.08Yb/0.005Tm/0.01Ho.