Synthesis And Photophysical Properties Of Titanate Based Red-Emitting Phosphor With Layered Structure For LEDs And FEDs

Nowadays,as the rapid development of white LED technology as well as the gradually mature technology of FED,the phosphors for white light-emitting diodes(w-LEDs)and field emission displays(FEDs)have attracted more and more attention of researchers,especially,the red phosphors which can be excited by UV or blue light This paper is focused on searching for efficient red phosphors with high stability and good conductivity matching well with the UV or blue LED chips.Eu3+-doped layered perovskite titanate solid state electrolytes based red phosphors for LEDs and FEDs were obtained by sol-gel method.Meanwhile,Mn4+-actived layered structure aluminate based red phosphors for LEDs were synthesized by conventional solid state reaction.The contributions and main work of the thesis are as follows:A series of layered perovskite titanate solid state electrolytes based red phosphors:ALnTiO4:Eu3+(A = Na,K;Ln = Gd,Y),A2Ln2Ti3O10:Eu3+(A = Na.K;Ln-Gd,Y,La)and La2Ti2O7:Eu3+ were synthesized via sol-gel reaction.The optimum synthesis conditions of these phosphors were determined.The structure phase was characterized by powder X-ray diffraction combined with the X-ray Rietveld refinement.The host electronic structure and the affiliation of host absorption were obtained based on the first principle calculation.The optical position of O2--Ti4+ host absorption was determined by the UV-visible spectrum combined with the host electronic structure.The comparison in luminescent properties,thermal-stability and cathode-luminescent properties of ALnTiO4:Eu3+(A = Na,K;Ln = Gd,Y),A2Ln2Ti3O10:Eu3+(A = Na,K;Ln = Gd,Y,La)and La2Ti2O7:Eu3+ phosphors was carried out systematically with the assist of the photoluminescence excitation(PLE),emission(PL)spectra,temperature-dependent PL spectra and cathode-luminescence(CL)spectra.The impedance properties of phosphors and the K+,Na+ ion diffusional pathways of the host were executed.The LED devices were fabricated by combining with the present red emitting phosphor Na2Gd0.6Eu1.4Ti3O10,Ca2B5O9Cl:Eu2+(blue)and Ca8Mg(SiO4)4Cl:Eu2+(green)tricolor phosphors and an n-UV chip(390 nm).The Ra,color temperature and CIE coordinates of the present W-LED is about 82,2151 K and(0.34,0.36).At the same time,on the account of the demand of red phosphors for both LEDs and FEDs.The obtained NaY0.7Eu0.3TiO4 phosphor with the strongest red emission,best thermal-stability and conductivity shows potential application value in LEDs and FEDs.Sr4Al14O25:Mn phosphor was prepared by conventional solid state reaction.The crystal structure,micro-morphology,and luminescent properties of this Sr4A14O25:Mn phosphor were characterized by X-ray Rietveld refinement,high-resolution transmission electron microscope(HRTEM)spectra,and photoluminescence spectra,respectively.Different valences of Mn ions in Sr4Al14O25 were determined by the X-ray absorption near-edge structure(XANES)spectroscopy technique.The crystal field environment effect of Al sites by introducing the activator Mn ions was investigated with the aid of Raman 27Al Nuclear Magnetic Resonance(NMR)spectra.The effects of pressure on the luminescent properties and decay time of this compound have been presented.The performances of the liquid-crystal displays(LCDs)have been obtained when the present phosphor combining blue InGaN chips and commercial ?-SiAlON:Eu2+ green phosphor for commercial applications.It is accessible for LCD display fabricated by LED backlighting.