Preparation And Luminesence Properties Of Rare-earth Doped Li₂La_xB_nO_3n+1 Phosphors

With the development of technique,luminescent materials are widely applied for many fields of human life such as fluorescence detection,light illumination and display screen.Perovskite compounds as an activator possesses because of stable chemical and thermal properties,are widely uesed for phophors.The general struc-ture of Ruddlesden-Popper?RP?phase is An+1BnO₃n+1,which could be written here as Li₂[AxBnO₃n+1]:?n = 2,3 and 4;A = La;B = Nb/Ti?.High temperature synthesis of the sample were prepared by Solid-state Method.The structure and lu-minescent properties of Li₂Lao,889Nb1.5Ti0.75O7?n = 2?and Li₂La_2.25Nb_1.25Ti_2.75O₁₃?n = 2?doped with Tb³⁺/Pr³⁺ ions are studied by characterization methods in-cluding X-ray diffraction?XRD?and fluorescence spectrum,respectively.The main contents are as follows:Li₂La_0.889Nb_1.5Ti_0.5O₇?n = 2?fluorescent powder was characterizated by XRD and fluorescence spectra.The results show that which was doped with a small amount of Pr³⁺ ions did not change the structure significantly.The excitation spectrum of Li₂La_0.889Nb_1.5Ti_0.75O₇:Pr³⁺ were mainly consisted of a wide band range from 200 to 400 nm.The peak is located at 278 and 339 nm,where the former peak near 278 nm originated from the 4f?5d transition of the Pr³⁺ ion;the latter peat near 339 nm is due to the valence-to-conduction.The emission band at 495 nm originated from ³P₀?P³H₄ transition of Pr³⁺ ions,the main peak in the emission spectrum located at 609 nm,which resulted from ¹D₂?³H₄ transition of Pr³⁺ ions.According to the XRD analysis,the main diffraction peaks of samples are con-sistent with the standard card?ICSD 88968?of the diffraction peak data.This showed doped rare earth ions did not change matrix lattice structure.The ex-citation spectrum of Li₂La_2.25Nb_1.25Ti_2.75O₁₃:Pr³⁺/Tb³⁺ consists of the 4f-5d excitation transition?278 nm?and valence-to-conduction?339 nm?and the valence charge transfer?IVCT?transition?360 nm?of Pr³⁺ to Ti⁴⁺.The emission spectra excited by 278 nm exhibit sharp lines peaking at 495 and 609 nm may assigned to the ³P₀?³H₄ and ¹D₂?³H₄ transition of pr3+ ions.In ordered to investigated the mechanism of energy transfer in host,excited under 237 nm,the emission spectrum of Li₂La_2.25Nb_1.25Ti_2.75O₁₃:Pr³⁺ sample has a broad emission band centered at 404 nm which can be assigned to the NbO67-complex transition of the host.Other weak peaks located in 495 and 609 nm as-cribed to the ³P₀?³H₄ and ¹D₂?³H₄ transition of Pr³⁺ ions.Furthermore,the luminescence of Tb³⁺-doped Li₂La_2.25Nb_1.25Ti_2.75O₁₃ has been investigated.As can be seen from the emission spectrum,there are a broad emission band centered at 404 nm and two shaxpe peaks located at 495 and 609 nm.Compared to Pr³⁺ ions,the substrate energy transfer to Tb³⁺ ions is more easy to occur.