Fluorescent Properties Of Tb³⁺-activated Rare-earth Fluorides Under VUV Excitation

The study of VUV phosphors becomes more extensive recently as the VUV phosphors are increasingly used for mercury-free lamps and the Plasma display plate (PDP).In order to improve the luminescent efficiency of the phosphors under high energy vacuum ultraviolet radiation(VUV) excitation,the properties of the host absorption band and the absorption of 4f^n-15d states and the energy transfer in the systems have been studied.The aim of this paper is mainly in research of the spectroscopic characteristics and the luminescent mechanisms of the electronic transitions at 4f⁸ levels and 4f⁷5d states of Tb³⁺ under VUV and ultraviolet(UV) excitation,the properties of the host absorption band,the factor that affect luminescence properties,and to find the routes of increasing the luminescent efficiency of the VUV phosphor by different synthesis methods.The results obtained in this thesis are as follows:1.The properties of the host absorption band in the range of VUV are studied, which of the rare-earth fluoride and aluminate doped with Tb³⁺,and properties of the absorption band of the Tb³⁺ ion's 4f-5d transition.The excitation spectrum reveals that the absorption band of the Tb³⁺ 4f-5d transition is roughly in the range between 170nm and 220nm in rare-earth fluorides.While in the oxysalt system,the splitting barycenter of the Tb³⁺ 4f-5d state energy is obviously lower.For instance in SrAl₁₂O₁₉:Tb³⁺,it is in the range between 230nm and 260nm.And the lowest positions of 4f⁷5d states of Tb³⁺ in different hosts are observed.2.Because of the wide forbidden bands in fluorides,the f-d transitions of Tb³⁺lie in higher energy position,avoiding overlap of f-f transitions.The products prepared by hydrothermal method show that the host absorption bands of rare-earth fluorides doped with Tb³⁺ was observed between 130nm and 160nm.And a broad host absorption bands of SrAl₁₂O₁₉:Tb³⁺ was observed between 140nm and 170nm.The absorption bands of the Tb³⁺ 4f⁸-4f⁷5d transition in SrAl₁₂O¹⁹:Tb³⁺ are in lower energy region than that of rare-earth fluorides,and as a host,fluorides can provide more information of rare-earth ions' 4f^n-15d states.