Synthesis and Luminescent Properties of GdNbO 4 :RE 3+ (RE = Tm, Dy) Nanocrystalline Phosphors via the Sol–Gel Process

Nanocrystalline GdNbO 4:Tm 3+ and GdNbO 4:Dy 3+ phosphors were prepared through a Pechini-type sol–gel process. X-ray diffraction, field emission scanning electron microscopy, transmission electron microscopy, photoluminescence, and cathodoluminescence (CL) spectra were utilized to characterize the synthesized phosphors. XRD reveals that the samples begin to crystallize at 900 °C and the pure GdNbO 4 phase can be obtained at 1000 °C. FE-SEM images indicate that the GdNbO 4:Tm 3+ and GdNbO 4:Dy 3+ samples consist of fine and spherical grains with a size around 30–50 nm. Under the excitation of UV light (264 nm) and low-voltage electron beams (1–3 kV), the GdNbO 4:Tm 3+ and GdNbO 4:Dy 3+ phosphors showed the characteristic emissions of Tm 3+ ( 1 D 2 → 3 H 6, 3 H 5, 3 H 4, and 1 G 4 → 3 H 6 transitions) and Dy 3+ ( 4 F 9/2 → 6 H 15/2 and 4 F 9/2 → 6 H 13/2 transitions), respectively. The blue CL of the GdNbO 4:Tm 3+ phosphor has higher color purity and comparable intensity to the Y 2 SiO 5:Ce 3+ commercial product. A single-composition white light emitting in response to near UV and low-voltage electron beam excitation has been realized in GdNbO 4:Dy 3+ phosphor. The obtained GdNbO 4:Tm 3+ and GdNbO 4:Dy 3+ phosphors have potential applications in the areas of near UV white-light-emitting diodes and field emission display devices.