Synthesis And The Up-conversionluminescence Performance Of Holmium Ytterbium Thulium Tri-doped Lithium Niobate Nanocrystals

With the continuous development of science and technology,rare earth doped photoluminescent materials have been widely used in laser,3-D display,holographic storage,fluorescent labeling and other fields for its upconversion luminescence performance.Lithium niobate?LiNbO₃?crystal has excellent piezoelectric,ferroelectric,nonlinear optical and acousto-optic properties,which known as one the most promissing candidate materials to achieve the integrated optical path of the next generation.LiNbO₃nanocrystals have an oxygen octahedral structure,which can achieve high concentration doping and have the advantages of low phonon energy and stable performance.Therefore,it is expected that rare earth doping can achieve high upconversion fluorescence performance.In this paper,LiNbO₃ nanocrystals were synthesized and their structures were optimized by sol-gel method.The upconversion luminescence properties of LiNbO₃nanocrystals were investigated by doping different rare earth elements and doping concentrations.Finally,white-light excitation was realized.Firstly,by related literature research and the distribution of energy levels of rare earth elements,holmium,ytterbium and thulium were chosen as the doping elements while matrix material was lithium niobate nanocrystals.The lithium-niobate nanocrystalline complex was prepared by sol-gel method.The rate of[Li]/[Nb]was close to 1.Doped with different concentrations of rare earth elements,and the samples were dried,sintered,ground and pressed to produce samples for optical experiments.Secondly,a series of tests were conducted on the samples,i.e.crystal structure test by the X-ray powder diffraction?XRD?,surface structure test by scanning electron microscopy?SEM?and material shape dispersibility test by the transmission electron microscopy?TEM?.The unit cell parameters,the composition of the material and the dispersibility and adhesion state of the nanocrystals were analyzed.Finally,Ultraviolet and Visible?UV-VIS?absorption spectra and upconversion luminescence properties were tested for the prepared samples.It was found that the UV-visible absorption reflectance spectrum was better,and the rare earth elements doped with different rare earth elements did a little affect the peak position of the UV spectrum.The holmium/ytterbium doped LiNbO₃ nanocrystals excited by the 980nm laser could emit visible green light,and the holmium/ytterbium/thulium doped LiNbO₃ nanocrystals excited by infrared gave a clear upconversion of white light.