Synthesis And Site Substitution Effect Of Titanate Multiphase Red Long Afterglow Phosphors

In three primary colors,luminescent intensity and afterglow time of green and blue long afterglow phosphors have reached the commercial application level.Many researchers have devoted to researching the red long afterglow phosphors,due to there are various reasons make it still not up to a wide range of applications.Red-emitting CaTiO3:Pr3+ phosphors have received extensive attention due to the excellent color purity,high chemical and physical stability.The excitation spectra of Ca0.82Zn0.2TiO3:Pr3+,Na+ phosphors consists of three bands.The excitation band around 330 nm is assigned to the valence-to-conduction band transition,The band around 330 nm is attributed to a low-lying Pr-to-metal(Pr3+/Ti4+ ? Pr4+/Ti3+)intervalence charge transfer state(IVCT).The weak peaks at 456,476,and 494 nm originate from 3H4 to 3PJ(J = V,1,2)transitions,respectively.It shows a strong red emission at 612 nm assigned to the 1D2 ?3H4.transition of Pr3+ions and its CIE coordinate(x = 0.680,y = 0.311)is very close to the ideal red.However,its luminescence intensity is not very high and the afterglow time is short.To improve the luminous efficiency of calcium titanate phosphors activated by Pr3+ ion is an important science and technology problem to be solved urgently in the field of red long afterglow phosphor.1.Effect of flux,the charge compensators and sensitizers on titanate red long afterglow phosphors.In this paper,H3BO3 were used as flux,Na2CO3?Li2CO3 and K2CO3 as flux and the charge compensators,and Bi3+ as sensitizer to improve the luminescent properties and the morphology of phosphors.Ca0.82Zn0.2TiO3:Pr3+ phosphors with different ion doped were prepared by the conventional solid-state reaction method and the optimum composition of the phosphors is obtained by orthogonal test..The experimental results show that all samples cosist of CaTi03,Zn2TiO4,and Ca2Zn4Ti16038 three phase.This shows that B3+,Na+,Li+,K+,Bi3+ are integrated into the host lattice and did not cause phase change obviously.The interband transition(VC)and charge transfer(IVCT)absorption increased significantly and made the phosphor for near UV excitation efficiency improve greatly.2.Effects of A/B site substitution on luminescent properties of phosphorsThis paper studied the effects of Zr4+,Al3+,Lu3+ codoping on the luminescence properties of phosphors.These ions are beneficial to the luminescent intensity increased to a certain extent,of which the most obvious effect of Zr4+.3.Effects of grading treatment on morphologies and luminescence properties of phosphorsThe luminous intensity of phosphor with water sieve grading treatment was lower than that of the same standard sieve mesh with dry sieve grading treatment significantly.The particle size of the former issmaller than the latter,and the phosphors below 500 mesh were the most obviously.the particle size of phosphors with 500 mesh decreases,but the particle agglomeration is serious,which limited its application.In addition,the luminous intensity of the phosphors above 500 mesh sieve is higher than above 500 mesh sieve,and has nothing to do with the grading treatment.4.Effects of synthesis process on morphology and luminescence property of phosphorsTwo kinds of synthetic processes of wet ball milling and hand milling can make the luminous intensity reach the same value,but the temperature of wet ball milling were lower than hand grinding..The particle size distribution of the former is more uniform and the particles size is much smaller.Thus the wet ball milling can reduce the synthesis temperature and change the morphology of phosphors.