Preparation And Optical Properties Of Eu²⁺ Doped Silicate Long Afterglow Luminescent Materials

Long persistent luminescence（Pers L）is a special optical phenomenon in which luminescence can last for seconds or even days after the light source stops.It has important applications in many fields,such as security and anti-counterfeiting,optical information and data storage,fingerprint recognition,analysis and sensing,optical imaging and treatment of tumors,and light-emitting diodes.After years of development,the research of Pers L materials has achieved fruitful results,but the development of Pers L materials also faces a series of new key problems due to the limitations of host and activators,such as unclear luminescence mechanism,poor stability and less color variety,which seriously limit their application fields.In this thesis,Pers L materials ranging from blue to yellow emission were prepared by co-doping rare earth ions(Ce³⁺and Tm³⁺)with high stability and low material cost silicate as the matrix material and Eu²⁺as the activator.And their application prospects were systematically investigated according to the trap distribution properties.By characterizing the thermo-luminescence profiles under different conditions（excitation time,waiting time after excitation,and variable temperature excitation treatment）,the trap continuum distribution,trap distribution modulation,and electron motion dynamics processes in the matrix materials were elucidated,and the following results and conclusions were obtained by combining the analysis of the series of characterization means:（1）A series of novel Na₃（Y,Sc）Si₃O₉:Eu²⁺Pers L phosphors were prepared by high-temperature solid-phase method,and the variation law of Pers L intensity under different Y/Sc ratios was explored.With the substitution of Sc ions,the Pers L intensity of the sample is enhanced first,and the best Pers L brightness and decay time are reached when Y:Sc=1:1,and the Pers L intensity gradually decreases as the substitution ratio continues to increase.Combined with the energy band engineering and thermo-luminescence spectroscopy analysis,the substitution of Sc³⁺ions can effectively regulate the depth of the defect energy level and the release rate of electrons.Finally,in this thesis,Na₃Y_0.5Sc_0.5Si₃O₉:Eu²⁺phosphors were prepared into thin films and their prospects for optical information storage applications were explored.（2）Multicolor-emitting Na₃Lu Si₃O₉:Ce³⁺,Eu²⁺Pers L phosphors were prepared by high-temperature solid-phase method.Under UV lamp irradiation,Na₃Lu Si₃O₉:Ce³⁺and Na₃Lu Si₃O₉:Eu²⁺exhibited the main peaks of 450 nm bright blue and 510 nm green emission,respectively.The energy transfer process and mechanism between Ce³⁺-Eu²⁺ions were investigated by analyzing the fluorescence lifetime.The color-tunable Pers L was obtained by modulating the doping concentration of different Ce³⁺/Eu²⁺ions.Finally,the application prospects of Na₃Lu Si₃O₉:Ce³⁺,Eu²⁺Pers L phosphors in the field of fingerprint identification and anti-counterfeiting were explored.（3）The blue-light-excited Ca₂Mg Si₂O₇:Eu²⁺,Tm³⁺Pers L phosphor was prepared by high-temperature solid-phase method.The material shows yellow-green emission under 450 nm blue light excitation,and bright yellow-green Pers L can be observed after the cessation of excitation.Meanwhile,the co-doping of Tm³⁺not only effectively increased the Pers L intensity of the phosphor,but also regulated the decay time of the Pers L of the phosphor.Finally,the LED devices were prepared by combining Ca₂Mg Si₂O₇:0.01Eu²⁺,0.01Tm³⁺with blue chips,and its application prospects in the field of AC-LED were explored.