Facile hydrothermal synthesis of Eu3+-activated NaYF4 nanocrystals and their Judd-Ofelt analysis, photoluminescence and cathodoluminescence properties

The Eu3+-activated NaYF4 nanocrystals were synthesized via a facile hydrothermal technique. The resultant compounds were characterized by X-ray diffraction pattern, transmission electron microscope images and photoluminescence (PL)/cathodoluminescence (CL) spectra. Under near-ultraviolet light excitation, the characteristic emissions of Eu3+ ions were detected in the prepared nanocrystals and the red emission at 615 nm originating from the 5D0 → 7F2 transition dominated in the emission spectrum. The luminescent spectrum revealed that the Eu3+ ions populated the low symmetry sites in NaYF4 lattices. Furthermore, a theoretical calculation based on the Judd-Ofelt theory was performed to evaluate the intensity parameters to further explore the local structure environment surrounding Eu3+ ions in NaYF4 lattices. The temperature-dependent PL emission spectra were recorded to study the thermal stability of the resultant nanocrystals and the activation energy was determined to be 0.149 eV. Ultimately, the CL properties of the final products as a function of accelerating voltage and filament current were investigated. These results revealed that the synthesized nanocrystals are a promising candidate for white light-emitting diodes and field emission displays as red-emitting phosphors.