Researches On The Synthesis And Luminescence Property Of Eu/Dy/Tm/Sm/Bi/Tb/Cr-doped Phosphors

With the progress of science and technology and the process of industrialization,LED has become a new generation of lighting technology,which has the advantages of energy-saving,high luminous efficiency,accurate light distribution,stability,reliability,long service life,and high cost-effectiveness.1-3 It has been widely used in urban road lighting,airports,docks,urban lighting projects,tourist attractions,and other places.Mainstream LED technology uses blue light to excite phosphors to achieve multi-color mixed light.The luminescent performance of phosphors has an important impact on the luminescent performance of LED devices,especially in the quality of luminescence.With the requirement of high color rendering index of LED lighting,the scheme of using blue or near ultraviolet LED chips to excite red,green,blue and yellow phosphors to form white light has been studied more and more.Persistent Luminescnece(PersL)is a particular phenomenon which can continue to glow after the excitation source is removed.To date,PersL materials have been widely applied in the fields of emergency command,information storage,living biological imaging and alternating LED lights.Especially in the application of in vivo imaging,they have many advantages over other biomarkers.For example,NIR PersLs can avoid strong absorption and scatter characteristics of visible light in tissues,and obtain high-performance optical imaging in vivo compared with visible light materials.However,the amount of gallium is exceedingly small in the earth's crust,and the high cost of gallium oxide as raw materials for synthesis of near-infrared luminescent materials has limited the mass production and application of such materials.So,it is necessary to develop a new kind of low cost near infrared PersL materials.In this work,we prepared a series of novel white LED phosphorsand long afterglow phosphors by solid state reaction and investigated their crystal structure,luminescence properties,energy transfer,afterglow properties and machenism in detail.The main contents are listed as below:1.The Na3Sc2(PO4)3 was used as the matrix material for the first time to synthesize phosphors with different colors,including blue light,yellow light,orange light and single matrix white light,by single doping or co-doping Eu2+,Dy3+,Tm3+and Sm3+,respectively.The fluorescence spectra,concentration quenching mechanism,thermal stability of each phosphor and the luminescence properties of packaged LED devices were studied.The results show that the phosphors based on Na3Sc2(PO4)3 have a good thermal stability and are easily excited by blue light or near ultraviolet.Blue phosphor of Na3Sc2(PO4)3:Tm3+can replace led blue chip to excite other phosphors.By adjusting the concentration ratio of co-doped ions,the white light of Na3Sc2(PO4)3:Eu2+,Dy3+and Na3Sc2(PO4)3:Tm3+,Dy3+ co-doped single matrix phosphor can emits adjustable light from the blue light to yellow light,and the single matrix phosphor of Na3Sc2(PO4)3:Eu2+,Sm3+can emits adjustable light from the blue light to orange light.2.For the first time,The BiCa4(PO4)3O was used as the matrix material to synthesize phosphors with different colors which were synthesized by single doping Dy3+ and Tb3+.In this paper,the fluorescence spectra,conceItration quenching mechanism,thermal stability of the two phosphors and the luminescent properties of the packaged LED devices were studied.The results show that BiCa4(PO4)3O:Dy3+and BiCa4(PO4)3O:Tb3+are easy to be excited by blue light or near ultraviolet light,and the distribution of BiCa4(PO4)3O:Dy3+and BiCa4(PO4)3O:Tb3+emit yellow light and yellow green light with a high brightness and good thermal stability.3.The Ba₃Y₄O₉ was used as the matrix material to synthesize phosphors with different colors which were synthesized by single doping or co doping Bi3+,Eu3+and Zn2+.In this paper,the fluorescence spectra,concentration quenching mechanism,thermal stability of the two phosphors and the luminescent properties of the packaged LED devices where studied.The results show that Ba₃Y₄O₉:Bi3+and Ba₃Y₄O₉:Eu3+are easily excited by blue light or near ultraviolet light.The Ba₃Y₄O₉:Bi3+,Ba₃Y₄O₉:Eu3+phosphors emit green light and orange light respectively.By adjusting the doping ratio of Bi3+and Eu3+,Ba₃Y₄O₉:Bi3+,Eu3+can emits adjustable light from green to orange.By adjusting the Zn2+doping concentration,Ba₃Y₄O₉:Bi3+,Eu3+,Zn2+can also emits adjustable light from green to orange.We speculate that Zn2+doping promotes the energy transfer from Bi3+ to Eu3+.The four materials have a high luminescent brightness and good thermal stability.4.The Mg1.4Zn0.6SnO4:Cr3+persistent luminescence was synthesized for the first time.The fluorescence spectrum,concentration quenching mechanism,thermal stability and afterglow properties of the long afterglow phosphor were studied.The results show that Mg1.4Zn0.6SnO4:Cr3+was easily excited by blue light or near ultraviolet light,and emits near-infrared light with the peaks of 708 and 730 nm.After 5 minutes of 460 nm excitation,the afterglow can last for 18 h.Compared with Mg2SnO4:Cr3+ luminescence,the luminescent brightness of Mg1.4Zn0.6SnO4:Cr3+is 2.87 times and 3.09 times of Mg2SnO4:Cr3+and Zn2SnO4:Cr3+when Zn2+is doped.The luminescent brightness of Mg2-xZnxSnO4:Cr3+ decreases when x exceeds 0.6.This provides a new idea for the development of Ga free NIR persistent luminescence.