Facile synthesis and enhancement upconversion luminescence of ErF3 nano/microstructures via Li+ doping

Abstract

A series of ErF₃ samples with different morphologies (flake, truncated octahedral, flower-like and rice-like microcrystals) and sizes (20 nm–2 μm) were prepared by an aqueous-based hydrothermal and coprecipitation route, respectively. The crystal structure of ErF₃ is firstly established via the Rietveld refinement result of the powder XRD data. In addition, the ErF₃ matrix without doping sensitizer or activator shows bright red upconversion emission under excitation at 980 nm. It is worthwhile pointing out that ErF₃ with an octahedral morphology demonstrates the highest relative intensity, with that of flower-like microcrystals following, but the nanoflakes show the lowest intensity, and the relative intensity is almost 8 times as low as that of the microcrystals. Further doping with Li⁺ would enhance the upconversion luminescence intensity, and the upconversion emission intensity of the optimal sample with doping 6 mol% Li⁺ is four times stronger than that of a Li⁺ free sample. Furthermore, upon electron beam excitation, the cathodoluminescence properties of a ErF₃ matrix as a new upconversion host are also studied, which is an interesting phenomenon.