Preparation Of Eu²⁺ Doped Fluorescence Materials And Application In White LED And Information Storage

Rare earth ion doped inorganic fluorescent materials have attracted much attention and widely studied by scholars,due to the superior and outstanding features,such as High luminous efficiency,stable chemical properties,adjustable spectrum,environmentally friendly。As one of the most widely used activators,Eu²⁺ions show typical f–d transitions.The luminescence wavelength of Eu²⁺varies from UV to blue,yellow and even red depending on the crystal filed environment。Based on the excellent optical properties of Eu²⁺,a series of luminescent materials for europium ion doped white LED（w LED）,long afterglow materials and light-excited long afterglow luminescent materials are synthesized in this paper。The phase structure of the synthesized samples was investigated by XRD,and the luminescence and thermal stability of the materials were characterized by steady state spectrum,diffuse reflection spectrum,high temperature spectrum,fluorescence life,thermoluminescence curve,and photoluminescence。The application prospect of the prepared material was also explored。The main research contents in this dissertation are summarized as follows:（1）Based on the zero thermal quenching,high quantum efficiency and blue light emission Na₃Sc₂（PO₄）₃:Eu²⁺phosphor material reported by Won Bin Im group,we adopted Eu²⁺→Tb³⁺,Eu²⁺→Mn²⁺energy transfer modes to achieve single-phase all-band emission in Na₃Sc₂（PO₄）₃host.By reasonably adjusting the doping ratio of Eu²⁺/Tb³⁺/Mn²⁺ions,the emission color can be adjusted from blue to green/red/white.Meanwhile,the steady state spectra,lifetime decay curves and energy transfer efficiency of Na₃Sc₂（PO₄）₃:Eu²⁺/Tb³⁺/Mn²⁺show that the concentration quenching mechanism between Eu²⁺and Tb³⁺/Mn²⁺is dipole-dipole interaction.Notably,the wide-gamut emission covering the full visible range of Na₃Sc₂（PO₄）₃:Eu²⁺/Tb³⁺/Mn²⁺gives an outstanding thermal quenching behavior-near zero thermal quenching at150℃/less than 20%emission intensity loss at 200℃,and high quantum yield-87.8%at 150℃/76.6%at 200℃.Moreover,the chromaticity coordinates of Na₃Sc₂（PO₄）₃:Eu²⁺/Tb³⁺/Mn²⁺keep stable through the whole evaluated temperature range（20-300℃）.Finally,a 365 nm near-UV w LED devices were fabricated,the whiteLEDdevice（CCT=4740.4K,Ra=80.9）indicatesthat Na₃Sc₂（PO₄）₃:Eu²⁺/Tb³⁺/Mn²⁺phosphor may be a promising candidate for phosphor-converted near-UV w LEDs.（2）A single-doped color tunable phosphors Na₃Sc_2-xAl_x（PO₄）_3-y（BO₃）_y:Eu²⁺are synthesized by conventional high temperature solid-state reaction method.The equivalent cation substitution of Sc³⁺by Al³⁺and unit substitution of（PO₄）^3-by（BO₃）^3-results in the significant distortion of the local environment neighboring the Na-O polyhedral,which enables the modulation of Eu²⁺occupation on three kinds of Na sites.This result leads to the significant widening of the Eu²⁺excitation and emission spectrum.By using the equivalent substitution of cations and anions,the Eu²⁺can not only occupy the Na1 lattice point,but also occupy the Na2 and Na3lattice points in Na₃Sc_2-xAl_x（PO₄）_3-y（BO₃）_yhost,which provides a new way for the design of full-color emission phosphors based on single-phase method.（3）For the first time a proof-of-concept study to develop an optical data storage（OSL）material with multi-dimensional traps for non-physical multi-level optically stimulated luminescence（ODS）has been successfully carried out by the facile incorporation of Dy³⁺,Tm³⁺and Ho³⁺into the BS:Eu²⁺host lattice.Various traps were intentionally introduced,presenting discrete energy levels of 0.72,0.84 and 1.02 e V within each narrow distributions of 0.073,0.088 and 0.107 e V.With the assistance of thermal cleaning,different information can be optically stored in the fabricated flexible phosphor film with different trap levels and then addressable level by level.Long term and recycling write-in and read-out measurements demonstrate good data retention and high fatigue resistance in data access.Despite its possible flaw and imperfection,the study of the as-obtained ODS material will help the researchers to gain insight into the complicated nature of traps,make leaps and bounds towards erasable multi-level ODS/high-security anti-counterfeiting,and provide a universal method to design new multi-level ODS media.