Synthesis,Structure And Warm-color Persistent Luminescence Properties Of Eu²⁺-doped Sr₃SiO₅-based Phosphors

Warm-color persistent luminescent materials are strongly desired for signage markings and medical imaging in comparison with green or blue counterparts.In this thesis,a series of Eu2+-doped Sr3SiO5-based warm-color long-persistent phosphors have been successfully synthesized through chemical coprecipitation and combustion method combined with high temperature solid-state reaction method.The synthesis,structure and luminescence properties have been studied systematically in order to meet the requirements of persistent luminescence applications.By optimizing the synthesis process,excellent-performance warm-color persistent luminescent materials were obtained,and its potential applications were explored.The main research contents and results are as follows:(1)Synthesizing a series of Sr3(Si1-xGex)O5:Eu2+(x=0.0～1.0)persistent luminescent phosphors.The persistent luminescence performance is obviously enhanced by Ge doping,and the sample with x=0.005 Ge4+substitution has the longest persistent about 7000 s.TL measurements and DFT calculations reveal that the enhanced persistent luminescence is due to Ge4+ addition,leading to more oxygen vacancies that act as electron-trapping centers with suitable trap depth.Futhermore,a HRBE model is constructed to explain the persistent luminescence mechanism in Sr3(Si1-xGex)O5:Eu2+phosphor.(2)We have designed and synthesized Sr3SiO5:Eu2+,TM(TM=Sc3+,Hf4+,Zr4+,Ti4+ Nb5+)persistent luminescent materials and systematically studied their performances.The sample doped with Nb5+ exhibits the longest persistence duration time of more than 14 hours,and the initial brightness over 1000 mcd/m2.Various measurements including TL,TLE,EPR and DFT calculations were used to study and clarify the persistent luminescent mechanism.Moreover,the potential applications of Sr3SiO5:Eu2+,Nb5+are shown.(3)Synthesis of the(Sr1-xBax)3SiO5:Eu2+,Nb5+(x=0～0.25)persistent luminescent materials by combustion method combined with solid-state reaction method.The change of Ba content not only can lead to a red shift of the persistent emission wavelength from 580 nm to 600 nm,but also can adjust the trap depth at a wide range.A systematic comparison on persistent luminescent performance of(Sr,Ba)3SiO5:Eu2+,Nb5+ and commercial warm-color persistent luminescence phosphors are carried out.(Sr0.88Ba0.12)3 SiO5:Eu2+,Nb5+has a very close CIE coordination with Y2O2S:Eu3+,Mg2+,Ti4+ and has a super long persistent decay time(about 16 hours).The results show that(Sr,Ba)3SiO5:Eu2+,Nb5+have excellent persistent luminescence performance,which maybe have great potential applications.