Energy Transfer and Tunable Luminescence of NaLa(PO₃)₄:Tb³⁺/Eu³⁺ under VUV and Low-Voltage Electron Beam Excitation

Abstract

Series of NaLa(PO3)4:Tb3+/Eu3+ phosphors were prepared by a high-temperature solid-state reaction technique. Structure refinements were performed based on powder X-ray diffraction (XRD) data. VUV–UV–vis photoluminescence (PL), fluorescence decays, time-resolved emission spectra (TRES), and low-voltage cathodoluminescence (CL) spectra were utilized to investigate the luminescence and energy transfer processes. Under VUV–UV light and low-voltage electron beam excitation, NaLa(PO3)4:Tb3+ and NaLa(PO3)4:Eu3+ exhibit characteristic emissions of Tb3+ (5D4 → 7FJ) and Eu3+ (5D0 → 7FJ), respectively. By adjusting the doping concentration of Eu3+ ions in NaTb0.70La(0.30-x)Eux(PO3)4, tunable emission colors are realized in a large color gamut, in which energy transfer from Tb3+ to Eu3+ was observed and discussed in detail. On the basis of the good VUV–vis PL and CL properties, NaLa(PO3)4:Tb3+/Eu3+ phosphors might be promising for applications in plasma display panels (PDPs) and field emission displays (FEDs).