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

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 (alpha-NaTbF4, beta-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.