Trap And Luminescence Properties Of Persistent Luminescenc Phosphor

In recent 20 years,persistent luminescence phosphors?PersL?has been developed unprecedentedly.A lot of novel PersL materials are exploited and applied.Recently,some silicate-based phosphors have been reported to show efficient PersL,and the silicates show some advances because of they being resistant to acid,alkali and oxygen.A novel orthosilicate persistent phosphor LiGa SiO₄:Mn²⁺has been developed by solid state reaction method.The refined crystal structure of the LiGaSiO4 is solved.It indicates that all cations are four coordinated by oxygen atoms and every cation connects with each other through tetrahedrons.The photoluminescence and persistent spectra,decay curve and thermoluminescence have been investigated in details.It reveals that the Mn²⁺at Li⁺sites in the LiO₄ tetrahedron are able to show intense green persistent luminescence,which can be measured for approximately 365 min and 125min?0.32 mcd/m2?after exposure to ultraviolet and artificial sunlight irradiation.The trap distribution of phosphor is studied by using a series of excitation temperature dependent thermoluminescence experiments based on initial rising method.According to the results,the LiGaSiO₄:Mn²⁺can be considered as an excellent PersL phosphor.Phosphors are efficient luminescence materials and have been extensively used in lighting and displays in today's world.However,the thermal quenching effect which the phosphor suffers from serious emission loss at high temperature is still one of the most significant challenges of the phosphors.We report a unique thermal sensitizing effect of the Na₂Ca Ge₆O₁₄:Pr³⁺phosphor,which the red emission of Pr³⁺is significantly enhanced with rising temperature,even up to 250°C.Also,the emission of the phosphor still keeps increasing over time at high temperature.This thermally induced emission increase originates from the generation of more defect levels and the more efficient energy transfer from the defects to Pr³⁺at higher temperature.This significant discovery may enlighten us a new strategy to minimize or even completely eliminate the serious thermally induced emission loss of the phosphors.