Shape-controllable hydrothermal synthesis of NaTbF4:Eu3+ microcrystals with energy transfer from Tb to Eu and multicolor luminescence properties

Abstract

Hexagonal NaTbF₄ microplates have been successfully synthesized through a simple hydrothermal method. X-ray diffraction (XRD), scanning electron microscopy (SEM), transmission electron microscopy (TEM), high-resolution transmission electron microscopy (HRTEM), inductively coupled high frequency plasma atomic emission spectroscopy (ICP-AES), photoluminescence (PL) and luminescence decay curves were used to characterize the samples. By optimizing the experimental conditions, such as Na-citrate consumption, pH value, reaction time and hydrothermal temperature, we obtained the samples with different components (NaTbF₄, TbF₃), crystal phases (α-NaTbF₄, β-NaTbF₄), and morphologies. A possible formation mechanism for the samples with different structures was proposed. In addition, the monodisperse hexagonal NaTbF₄ microplates, which can be used as an excellent host lattice for Eu³⁺ ions, and the multicolor luminescence properties of NaTbF₄ with various Eu³⁺ doping concentrations have been studied. At the same time, the energy transfer from Tb³⁺ to Eu³⁺ in NaTbF₄:x%Eu³⁺ (x = 0–1) was also investigated. The color of the NaTbF₄:x%Eu³⁺ (x = 0–1) samples can be varied from green to red by adjusting the doping concentration of Eu³⁺, which exhibits a good advantage of multicolor emissions in the visible region, and endows this material with potential application in many fields, such as light display systems, optoelectronic devices and biological imaging. Such a simple synthetic method is also useful for the synthesis of other complex rare earth fluorides with hexagonal architectures.