Luminescent Properties in Relation to Controllable Phase and Morphology of LuBO₃:Eu³⁺ Nano/Microcrystals Synthesized by Hydrothermal Approach

Abstract

The calcite and vaterite type LuBO 3 :Eu 3+ nano/microcrystals with various morphologies were synthesized by the hydrothermal (HT) approach through controlling the pH values of the precursor solutions. The calcite type LuBO 3 :Eu 3+ shows the dominant magnetic dipole 5 D 0 -7 F 1 emission due to S 6 inversion symmetry of Lu. It also shows a symmetrical O-Eu charge transfer (CT) excitation band, which, however, is asymmetrical and broad in the material prepared by the solid-state (SS) reaction method. The effect of the residual OHgroups introduced in HT synthesis is discussed on O-Lu exciton annihilation and local environment distortion. Two different Eu 3+ centers, one of which is with inversion symmetry, are observed in vaterite type LuBO 3 :Eu 3+ . The HT sample with nanostructures, such as vaterite type flowerlike LuBO 3 :Eu 3+ , demonstrates a red shift of the CT band and appearance of a long excitation tail at the long wavelength side of the CT band. XRD, selective excitation and fluorescence decay measurements indicate that the red shift is induced by an increase of crystal lattice parameters, and the excitation tail is responsible to the Eu 3+ ions located at lower symmetric sites. These sites are attributed to the positions at or close to the surface of the nanostructures in the sample. As the lower symmetric sites are selectively excited, the red emission of 5 D 0 -7 F 2 of Eu 3+ enhanced twice relatively to the orange emission of 5 D 0 -7 F 1 , exhibiting superior color chromaticity in red for display application. The luminescence properties of interior Eu 3+ and outside Eu 3+ are studied and discussed in detail.

Phase formations and tunable red phosphors of LiYb1−Eu (MoO4)2 (x = 0.01–1)

“…The excitation spectra consist of broad charge transfer (CT) band and some narrow lines. The CT band peaking around 315 nm is originated from the charge transfer transition of O 2-→ Eu 3+ [23][24][25]. The CT band extends with the full-width at half-maximum of about 6970 cm -1 and shows no significant change in spectral shape for x = 0.01-1.0 as shown in Fig.…”

Спектральные и структурные характеристики ортоборатов Lu-=SUB=-1-x-y-=/SUB=-Ce-=SUB=-x-=/SUB=-Tb-=SUB=-y-=/SUB=-BO-=SUB=-3-=/SUB=-, полученных методом гидротермального синтеза

“…• C в автоклаве [5][6][7][8][9][10]. Продуктом такого синтеза являются частицы шарообразной формы размером 5−10 µm, состоящие из наноразмерных эле-ментов, имеющих форму пластин.…”

“…При этом определен-ная структурная модификация (кальцит или ватерит) мо-жет быть получена при разных величинах кислотности водной реакционной среды [7]. В работах [5][6][7][8][9][10] …”

Synthesis and luminescent properties of subglobose YBO3:Ln3+(Eu, Tb) phosphors

“…Rare-earth borate (ReBO 3 )-based phosphors are one category of useful luminescent materials with strong luminescent intensity, high chemical stability and low toxicity [4][5][6][7]. Among the REBO 3 phosphors, YBO 3 has been proved to be a very effective host crystal for the luminescence of Eu 3?…”