Band structure, shape controllable synthesis and luminescence properties of the precursor and final product Lu6O5F8:Eu/Tb/Ce/Dy nano/microstructures

Abstract

In the present paper, the band structure and density of states of Lu₆O₅F₈ were primarily studied with the help of first-principles calculations, and the indirect band gap of Lu₆O₅F₈ is estimated to be 4.13 eV wide. Lu(OH)_1.57F_1.43/NH₄Lu₂F₇/Lu₆O₅F₈ nano/microcrystals with diverse morphologies, sizes and dimensions have been synthesized via a mild and controllable hydrothermal process using citric acid trisodium salt dehydrate (Cit³⁻), hexadecyltrimethylammonium bromide (CTAB), ethylenediaminetetraacetic acid (EDTA), ethylenediaminetetraacetic acid disodium salt (EDTA²⁻), sodium dodecyl benzene sulfonate (SDBS), ethylenediamine (EA) or polyvinylpyrrolidone (PVP), etc. as an additive, respectively. The phases, morphologies, sizes, and luminescence properties of the as-prepared samples were well characterized by means of X-ray diffraction (XRD), scanning electron microscopy (SEM), transmission electron microscopy (TEM), photoluminescence (PL) and cathodoluminescence (CL) spectroscopy, respectively. The results indicate that the phase, morphology, and size of Lu(OH)_1.57F_1.43/Lu₆O₅F₈ can be tuned in a controlled manner by altering the amount or kinds of additives, the pH values of the initial solution, and the reaction time. Furthermore, the time-dependent morphology evolution shows that the resulting microrods, hexagonal prisms, flower clusters and spheres were synthesized by a dissolution–reconstruction formation mechanism. It is expected that the synthetic strategy can be extended to controllable synthesis of other types of nano/microcrystals as well. Upon ultraviolet (UV), vacuum ultraviolet (VUV) and electron beam excitation, the luminescence properties as well as the emission mechanisms of the Ln³⁺ (Ln = Eu/Tb/Ce/Dy) single doped precursor (NH₄Lu₂F₇, Lu(OH)_1.57F_1.43) and final product (Lu₆O₅F₈) are all compared and studied. All in all, the multifunctional Ln³⁺ doped NH₄Lu₂F₇/Lu(OH)_1.57F_1.43/Lu₆O₅F₈ nano/microcrystals have potential applications in photoluminescence areas and field emission display devices.