Preparation And Photoluminescence Properties Of Titanate Red Phosphor For White Light Emitting Diodes

White light-emitting diodes(WLEDs)were called the fourth generation light source because of the advantages of low energy consumption and green environmental protection.WLED also attracted many research workers for its extension of application and great potential in lighting devices.The red phosphors in tricolor WLED demand most and affect directly the color rendering,therefor it is important to develop excellent performance red phosphors.In this paper,sol-gel method was used for the preparation of samples.Firstly,The samples of ZnTiO3 and Zni-xTiO3:xEu3+ had been prepared.The photoluminescence(PL)showed the phosphors present red emission at 615nm under the excitation of 393nm and 464nm.The phosphors exhibit strongest red emission when selected 2 mol%Eu3+ as doping concentration calcined at 700? for 4h.Besides,the color purity values are closer to Commission Internationale de L'Eclairage(CIE)standard than the commercial red phosphor.A series of red-emitting phosphor ZnTiO3:Eu3+ co-dopped with alkali metals ions(Li+,Na+ and K+)was synthesized for the first time by sol-gel method.The influence of site occupancy of alkali metals ions(A+)on the emission of ZnTiO3:Eu3+ was investigated in detail.It could be found that the positions of characteristic peaks for A+-doped samples have no distinct variation in comparison with the sample without A+.The emission intensity was significantly enhanced by introducing different concentrations of A+ ions.In contrast to A+-free ZnTiO3:Eu3+,the red emission intensities of the ZnTiO3:Eu3+ codoped with 4 mol%Li+,Na+ and K+ ions were enhanced by about 2.14,1.55 and 1.45 times,respectively.Sr1-xTiO3:xEu3+ red phosphors were also prepared by sol-gel method.The XRD and TEM results showed the samples were of cubic phase.The excitation and emission spectra results indicated the Sr1-xTiO3:xEu3+ could be excited by 393 nm and 464 nm,then emitted 580 nm,591nm 617 nm light.When x=4%,the samples showed the best luminous intensity.Based on 4%Eu3+ concentration,the A+ were added to improve luminous intensity,the results showed the sample with 4%K+ doped showed the best enhanced effective.First principles was used to calculate Eu3+ doping,Eu3+/Li+ co-doped ZnTiO3 and SrTiO3 electronic structure and optical properties.The results show that Eu 4f impurity states may appear in the forbidden band,reduces the pure phase of the band gap,Eu3+/Li+ doping of synergies to enhance the coupling between various electronic,promote the energy transfer between system..In addition,the optical absorption spectrum show that there is an obvious light absorption of red shift phenomenon in ZnTiO3:Eu3+,Li+ and SrTiO3:Eu3+,Li+,and showed a stronger light absorption ability in low energy region,the results indicated that Eu3+/Li+ doping can well enhance luminous intensity in the visible region,which is consistent with experimental results.