LaOF : Eu3+nanocrystals: hydrothermal synthesis, white and color-tuning emission properties

Abstract

Uniform LaOF and LaOF : Eu³⁺ nanocrystals of the γ-form have been successfully synthesized under mild conditions via a facile hydrothermal method followed a heat treatment of their bastnaesite-type precursor (LaCO₃F). The synthetic details, investigations into the phase purity and the presence of the oxocarbonate anion CO₃^2– proven by IR measurements and EDX, as well as X-ray powder diffraction data, are given. Photoluminescence (PL) and cathodoluminescence (CL) spectra were utilized to characterize the luminescence properties of the LaCO₃F : Eu³⁺ and LaOF : Eu³⁺ samples. Under ultraviolet light excitation, the LaCO₃F : Eu³⁺ precursor shows an orange emission of Eu³⁺ (dominated by ⁵D₀ → ⁷F₁), while the product of heat treatment, LaOF : Eu³⁺, shows the characteristic emissions of Eu³⁺ (⁵D_J → ⁷F_J′J, J′ = 0, 1, 2, 3 transitions). Under the excitation of UV and low-voltage electron beams, the emission color (including white) of LaOF : Eu³⁺ can be tuned by adjusting the doping concentration of Eu³⁺. The corresponding luminescence mechanisms have been discussed in detail.