Preparation And Photoluminescent Properties Of Ln-Doped Layered Potassium Lanthanoniobate Phosphors

Luminescence materials has wide application prospects in optical display,lighting project, photoelectric detection, biological marker, medical diagnosis andtreatment area. The development of new luminescence materials with energy efficientis one of the current research hotspot. The layered perovskite KLaNb₂O₇’s structure isstability, and has good mechanical properties and physical and chemical properties.This paper chooses KLaNb₂O₇as the object of our study. The intralayer dopedcompounds was prepared and then exfoliated to nanosheets. After restacking, thenanosheets multiple films and interlayer-intercalated compounds were prepared. Thestructures, morphologies, thermal stability and luminescence properties of theluminescent materials were characterizated by means of XRD, fluorescence spectra,UV-Vis, IR, XPS, SEM, TEM and so on.Rare-earth ions doped KLa_0.95-xLn_xNb₂O₇(Ln=Dy³⁺、Er³⁺)were prepared by asolid state reaction. Within certain range of concentrations, the doped potassiumlanthanum niobate maintains the same layered structure，its absorption wavelenghhave blue-shifted and the optimal doping of rare earth ions is5%. Thephotoluminescence emission of KLa_0.95-xLn_xNb₂O₇via host excitation is negligiblylow in intensity, whereas the emission via direct Ln³⁺excitation has apparently beenobserved. On the contrary, the emission via host excitation becomes far morepredominant than that via direct Ln³⁺excitation for the La_0.90Ln_0.05Nb₂O₇nanosheet.(PEI/La_0.90Dy_0.05Nb₂O₇)nmultiple films was obtained by layer-by-layer method.And then treated it by heat or UV light. The AFM data suggested that the averageheight of a single La_0.90Dy_0.05Nb₂O₇nanosheet was1.13nm. Both the as-preparedmultiple films and its post-treated products displayed stonger hostexcitation-Mediated photoluminescence origined from O₂^-�'Dy³⁺and O–Nb�'Dy³⁺energy transfer. While there was not observed emission from direct Dy³⁺excitation.Utilizing the exfoliation and restacking properties of lanthanum niobate, Dy³⁺、Er³⁺-intercalated lanthanum niobate layered nanocomposites assembled from niobatelayer and Dy³⁺, Er³⁺have been successfully prepared. The gallery height ofnanocomposite increased about0.37and0.33nm. Thermal analyses suggested that the resulting meterial shows good thermal stability. The analysis results by UV-Vis,XPS suggested there is some strong interaction between hosts and guests which madethe intercalated composites’s absorption wavelengh red-shifted and the biding energyof Nb3d,La3d,O1s increased. The fluorescence results suggested that the emissionvia direct Ln³⁺excitation was far more predominant than that via host excitation forboth the as-prepared intercalated compounds and its post-treated products. After heattreated the direct Ln³⁺excitation intensity was increased,while the host excitationweakened.