The Luminescence Properties Of Rare Earth Doped Silicate Aluminate Phosphors

Light-emitting diodes（LEDs）are highly concerned for their high efficiency,long lifetime,energy saving and environmental protection.With the improvement of the blue and near-ultraviolet LED chips,white light LEDs with"LED chip+phosphor"technology has become the research focus.Phosphors are an important part of the current white LED equipment manufacturing.Therefore,it is important to looking for phosphors which with high color rendering,high thermal stability and other excellent luminous properties and study their light-emitting principle.In this thesis,a series of aluminosilicate luminescent materials with different luminescence centers have been explored.The specific relationship between the lattice environment and the luminescence properties of the materials have been studied systematically.The main experimental results of this paper are as follows:（1）A series of Eu³⁺doped NaMSi₂O₆（M=Y,Sc）phosphor samples were successfully synthesized by high temperature solid phase method.The XRD data of the prepared samples confirm that the prepared samples are the target product NaMSi₂O₆（M=Y,Sc）:Eu³⁺.Upon393nm excitation,all the samples exhibit a characteristic emission peak of Eu³⁺near 614nm.Comparing the(I_{（5D0-7F2）}/I_{（5D0-7F1）})of NaScSi₂O₆:Eu³⁺and NaYSi₂O₆:Eu³⁺,the value of NaScSi₂O₆:Eu³⁺is higher.The local asymmetry value（D）around the luminescence center is D_Sc=0.0654,D_Y=0.0506.Finally,the activation energies of NaYSi₂O₆:0.12Eu³⁺and NaScSi₂O₆:0.12Eu³⁺were calculated to be 0.4709 eV and 0.1766 eV respectively,which shows that both two samples have good thermal stability.（2）Here,CaLa₉（AlO₄）（SiO₄）₅O₂:Eu³⁺and SrLa₉（AlO₄）（SiO₄）₅O₂:Eu³⁺and Ba La₉（AlO₄）（SiO₄）₅O₂:Eu³⁺were synthesized by the high temperature solid phase method.The crystal structure of the prepared sample were determined by XRD,the emission spectrum of each sample was obtained.According to the CIE coordinates,the color purity of SrLa₉（AlO₄）（SiO₄）₅O₂:x Eu³⁺is higher than the two other matrix samples.The thermal stability was also investigated and the CaLa₉（AlO₄）（SiO₄）₅O₂:0.16Eu³⁺is the best.（3）A series of Eu²⁺doped SrLa_9-xSc_x（AlO₄）（SiO₄）₅O₂:0.03Eu²⁺and SrLa₄Sc₅（AlO₄）（SiO₄）₅O₂:Eu²⁺were synthesized by high temperature solid phase method.The experimental results of SrLa₄Sc₅（AlO₄）（SiO₄）₅O₂:Eu²⁺show that as Sc³⁺gradually replaces La³⁺,the luminous intensity of the samples increase first and then gradually decrease.The number of luminescent centers in the samples are determined using fluorescence lifetime data and emission spectrum analysis.The energy transfer mechanism is calculated based on the relationship the emission spectrum intensity（I）and the doping concentration of Eu²⁺（x）.The red shift or blue shift of the emission spectrum is explained using centroid displacement and crystal field intensity.The activation energies of SrLa₄Sc₅（AlO₄）（SiO₄）₅O₂:0.07Eu²⁺were calculated to be 0.2818eV,indicating that the thermal stability of the samples is excellent.（4）In this part,Ce³⁺and Tb³⁺based on NaYSi₂O₆ is mainly explored.The crystal structure of the prepared materials was determined by XRD.The fluorescence lifetime and emission spectrum prove that an energy transfer phenomenon between Ce³⁺and Tb³⁺.The energy transfer mechanism of NaYSi₂O₆:Ce³⁺,Tb³⁺is electric dipole-electric dipole interaction.The luminous intensity of NaYSi₂O₆:0.01Ce³⁺,0.25Tb³⁺at different temperatures shows that the activation energy of the samples is 0.2837 eV.