Synthesis and Luminescent Properties of GdNbO4:RE3+ (RE = Tm, Dy) Nanocrystalline Phosphors via the Sol-Gel Process

Nanocrystalline GdNbO4:Tm3+ and GdNbO4:Dy3+ 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 degrees C and the pure GdNbO4 phase can be obtained at 1000 degrees C. FE-SEM images indicate that the GdNbO4:Tm3+ and GdNbO4:Dy3+ 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 GdNbO4:Tm3+ and GdNbO4:Dy3+ phosphors showed the characteristic emissions of Tm3+ (D-1(2) -> H-3(6), H-3(5), H-3(4), and (1)G(4) -> H-3(6) transitions) and Dy3+ (F-4(9/2) -> H-6(15/2) and F-4(9/2) -> H-6(13/2) transitions), respectively. The blue CL of the GdNbO4:Tm3+ phosphor has higher color purity and comparable intensity to the Y2SiO5:Ce3+ commercial product. A single-composition white light emitting in response to near UV and low-voltage electron beam excitation has been realized in GdNbO4:Dy3+ phosphor. The obtained GdNbO4:Tm3+ and GdNbO4:Dy3+ phosphors have potential applications in the areas of near UV white-light-emitting diodes and field emission display devices.