Tm3+ and/or Dy3+ doped LaOCl nanocrystalline phosphors for field emission displays

Abstract

Blue, yellow and white light emissive LaOCl:Tm³⁺, LaOCl:Dy³⁺ and LaOCl:Tm³⁺,Dy³⁺ nanocrystalline phosphors were synthesized through the Pechini-type sol-gel process. X-Ray diffraction (XRD), field-emission scanning electron microscopy (FE-SEM), photoluminescence (PL) and cathodoluminescence (CL) spectra were used to characterize the samples. Under UV radiation (229 nm) and low-voltage electron beam (0.5–5 kV) excitation, the Tm³⁺-doped LaOCl phosphor shows a very strong blue emission corresponding to the characteristic transitions of Tm³⁺ (¹D₂, ¹G₄ → ³F₄, ³H₆) with the strongest emission at 458 nm. The cathodoluminescent color of LaOCl:Tm³⁺ is blue to the naked eye with CIE coordinates of x = 0.1492, y = 0.0684. This phosphor has better CIE coordinates and higher emission intensity than the commercial product Y₂SiO₅:Ce³⁺. Notably, for the first time, white cathodoluminescence was realized by co-doping Tm³⁺ and Dy³⁺ with appropriate ratios in the LaOCl single host lattice, which can be potentially used as backlights. Luminescence mechanisms were proposed to explain the observed phenomena.