Studies On The Surface Modification And Application Of SrAl₂O₄:Eu²⁺, Dy³⁺ Phosphor

SrAl₂O₄:Eu²⁺,Dy³⁺ phosphor has been accepted as one of the most important long afterglow luminescent materials,due to the advantages of its wide excitation spectrum,visible emission spectrum range,high luminescent intensity,long afterglow duration,well chemical stability,no radiation,no toxicity,safety and environmental capability.It is widely used in many fields of our life.However it is easy to hydrolyze in the moist place.The luminescent ability of the material will degrade continually with the hydrolysis reaction proceeding,and finally this ability will disappear thus to make the material useless.The bad dispersibility of powder in the organism also affects the performance of the luminescent composite materials. Besides,Eu²⁺ is easily oxidized to Eu³⁺ at high temperature which will affect its luminescent performance.So the surface modification is necessary to improve the phosphors' performance.Research status of the SrAl₂O₄:Eu²⁺,Dy³⁺ long afterglow material was systematically summarized in this paper especially that of the material's surface modification and its application in luminescent coating.Technologies of inorganic encapsulation,organic modification and inorganic/organic modification were used for the surface treatment of phosphors respectively.Optimize the encapsulation conditions,summarize and analyze the reaction results by testing dates and discuss the reaction mechanism.Finally we manufactured the luminescent coating with fine performance.(1)In order to improve the material's water-resistance and temperature stability, technologies of SiO₂ and Al₂O₃ "nonhomogeneous phase coring" inorganic encapsulation were used on the phosphors.The results show that when the covering amount of SiO₂ is over 8%and that of Al₂O₃ is over 15%it can form complete and compact coating layer.The results show that silica encapsulation can effectively improve phosphors' water-resistance and the temperature stability increases by 50%.Especially the intensity of the encapsulated phosphors increases by 10%than that of the unencapsulated phosphors,which is very positive for the application of phosphors.(2) In order to improve the dispersibility of phosphor,etherification organic modification with long-chain alcohol were used for the surface treatment.The effects of process conditions on phosphors' performances were investigated.Dodecyl encapsulation can turn the hydrophilic surface to hydrophobic surface of phosphors at 7%loss of photoluminescence,but the water-resistance is not very well.The contact angle between phosphor and water increases by 86.5°.SiO₂/dodecyl encapsulation can improve phosphors' oil proximity as well as the water-resistance,and the loss of photoluminescence is lower than 8%.The contact angle between phosphor and water increases by 86.8°.In this paper,we finally developed the best formula of luminescent coating,namely to use the encapsulated phosphors as filler pigments,the acrylic acid varnish as the binder and with appropriate sub reagents we manufactured the luminescent coating.Then we tested its relevant performances.The optimal addition level of phosphors is 10-30%,and the coating possesses good stock stability and water-resistance.The coating accords to related standard,so it can be used as outdoor traffic signs,etc.