Nanocrystalline CaYAlO4:Tb3+/Eu3+ as promising phosphors for full-color field emission displays

Abstract

Eu³⁺ and/or Tb³⁺-doped CaYAlO₄ phosphor samples were synthesized by Pechini-type sol–gel method. X-Ray diffraction (XRD), field-emission scanning electron microscopy (FE-SEM), photoluminescence (PL) and cathodoluminescence (CL) spectra were used to characterize the samples. For CaYAlO₄:Tb³⁺, it is shown that the Tb³⁺-doping concentration has a significant effect on the ⁵D₃/⁵D₄ emission intensity of Tb³⁺, which is attributed to the cross relaxation from ⁵D₃ to ⁵D₄. Under the 4f⁸ → 4f⁷5d excitation of Tb³⁺ or low-voltage electron beams excitation, the CaYAlO₄:Tb³⁺ phosphors show tunable luminescence from blue to cyan, and then to green with the change of Tb³⁺-doping concentration. The CaYAlO₄:Eu³⁺ samples exhibit a reddish-orange emission of Eu³⁺ corresponding to ⁵D_0,1 → ⁷F_0,1,2,3 transitions. Furthermore, a white emission can be realized in the single phase CaYAlO₄ host by reasonably adjusting the doping concentrations of Tb³⁺ and Eu³⁺ under low-voltage electron beams excitation. Compared with the commercial blue (Y₂SiO₅:Ce³⁺) and green (ZnO:Zn) phosphors, CaYAlO₄:0.1%Tb³⁺ and CaYAlO₄:5%Tb³⁺ phosphors have higher CL intensity and stability under continuous electron bombardment. Due to the excellent CL properties and good CIE chromaticity coordinates, the as-prepared Tb³⁺/Eu³⁺-doped CaYAlO₄ nanocrystalline phosphors have potential application in FEDs devices.