Energy Transfer and Tunable Luminescence Properties of Eu³⁺ in TbBO₃ Microspheres via a Facile Hydrothermal Process

Abstract

Tb (1- x) BO 3: xEu (3+) ( x = 0-1) microsphere phosphors have been successfully prepared by a simple hydrothermal process directly without further sintering treatment. X-ray diffraction (XRD), Fourier transform infrared spectroscopy (FTIR), thermogravimetric analysis (TGA), scanning electron microscopy (SEM), transmission electron microscopy (TEM), high-resolution transmission electron microscopy (HRTEM), selected area electron diffraction (SAED), photoluminescence (PL), low-voltage cathodoluminescence (CL), and time-resolved emission spectra as well as lifetimes were used to characterize the samples. The as-obtained phosphor samples present sphere-like agglomerates composed of nanosheets with highly crystallinity in spite of the moderate reaction temperature of 200 degrees C. Under ultraviolet excitation into the 4f (8) --> 4f (7)5d transition of Tb (3+) at 245 nm (or 284 nm) and low-voltage electron beams' excitation, TbBO 3 samples show the characteristic emission of Tb (3+) corresponding to (5)D 4 --> (7)F 6, 5, 4, 3 transitions; whereas TbBO 3:Eu (3+) samples mainly exhibit the characteristic emission of Eu (3+) corresponding to (5)D 0 --> (7)F 0, 1, 2, 3, 4 transitions due to an efficient energy transfer occurs from Tb (3+) to Eu (3+). The increase of Eu (3+) concentration leads to the increase of the energy-transfer efficiency from Tb (3+) to Eu (3+) but also enhances the probability of the interaction between neighboring Eu (3+), which results in the concentration quenching. The PL color of TbBO 3: xEu (3+) phosphors can be easily tuned from green, yellow, orange, to red-orange by changing the doping concentration ( x) of Eu (3+), making the materials have potential applications in fluorescent lamps for advertizing signs and other color display fields.