Host-sensitized luminescence of Dy3+ in LuNbO4 under ultraviolet light and low-voltage electron beam excitation: energy transfer and white emission

Abstract

A series of LuNbO₄:xDy³⁺ (x = 0–0.20) phosphors was prepared using a high-temperature solid-state reaction technique. X-ray diffraction (XRD) along with Rietveld refinement, field emission scanning electron microscopy (FE-SEM) observations, diffuse reflectance spectra (DRS), UV-vis photoluminescence (PL), fluorescence decays, PL quantum yields (QYs), and low-voltage cathodoluminescence (CL) were employed to characterize the phosphors. Nonradiative relaxation and host sensitization dramatically influence the LuNbO₄:Dy³⁺ luminescence spectra and decay dynamics. It is shown that cross-relaxation arising from electric dipole–dipole interactions between adjacent Dy³⁺ ions is the leading mechanism of quenching the Dy³⁺ emission. The host sensitization for Dy³⁺ emission in LuNbO₄ was confirmed and the energy transfer efficiency from the host to Dy³⁺ increased with increasing Dy³⁺ doping concentration/temperature. Upon excitation with ultraviolet light (261 nm) and a low-voltage electron beam (2 kV, 127 μA cm⁻²), the synthesized LuNbO₄:Dy³⁺ phosphors show both the blue broadband emission of the LuNbO₄ host and the characteristic emission of Dy³⁺ (the dominant one is the ⁴F_9/2 → ⁶H_13/2 transition, yellow), and the luminescence colour of the LuNbO₄:Dy³⁺ phosphors can be tuned over a large gamut of colours by varying the Dy³⁺ doping concentration, and a single-phase intense white-light-emission has been achieved in the LuNbO₄:0.015Dy³⁺ phosphor. On the basis of the good UV-vis PL and CL properties, LuNbO₄:Dy³⁺ phosphors might be promising for applications in UV light-emitting diodes (UV-LEDs) and field emission displays (FEDs).