Preparation of size-controlled nanocrystalline infrared-to-visible upconverting phosphors Gd₂O₃:Yb,Er by using a water-in-oil microemulsion system

Nanocrystalline infrared-to-visible upconverting phosphors Gd₂O₃:Yb,Er with narrow size distribution were prepared by using a microemulsion system (MES) of stability, which includes phases of Triton X-100 (surfactant phase (s)), n-hexanol (assistant surfactant phase (As)), cyclohexane (oil phase (O)) and solution (water phase (W)). From the microemulsion system we could get appearance-controllable nanocrystalline by adjusting the ratio of oil and surfactant. The X-ray diffraction results showed that the powders were cubic phase of Gd₂O₃ after being calcined in the air at 1273 K. The scanning electronic microscopy revealed that the particles were spherical. Red and green upconversion luminescences were obtained by 980 nm infrared excitation. We also investigated contributions of different ratio of surfactant to the appearance.