Preparation And Luminescence Properties Of Silicon-based Nitrogen Oxide Phosphors

In today's society,car have penetrated into every aspect of our lives.The application of LED in car field has undergone a lot of evolution.Compared with halogen lamps and xenon lamps,the W-LEDs which based on phosphorus conversion technology have some advantages in low cost,environmental protection,small volume,high efficiency and long service life.At present,the W-LEDs which used in most companies are blue light chips combined with yellow light emitting phosphors.However,due to the limitation of its red luminescence area,this combination has obvious disadvantages in color development index?CRI?and color temperature?CCT?.In recent years,the W-LEDs of n-UV chips with tricolor phosphors?blue,green and red?have been attracted more and more attention due to their high chromogenic index and uniform chromooptic properties.Therefore,it is an important task to find a single phase tricolor phosphor which suitable for n-UV W-LEDs.In this paper,we investigated the luminescence properties of silica-based nitrous oxide which doped with different rare earth ions.Firstly,a series of novel blue emitting phosphors?Ba,Sr?Al₂Si₃O₄N₄:Eu²⁺and red emitting phosphors BaAl₂Si₃O₄N₄:Mn²⁺,Sm²⁺were successfully prepared by two-steps high temperature solid state reaction under reducing atmosphere.By means of finishing,spectral characterization,energy band and state density calculation,the crystal structure and luminescence properties were studied.Gaussian fitting was performed for the emission spectrum of BASON:Eu²⁺to explain the asymmetry of Eu²⁺emission peaks in BASON.The luminescence intensity of(Ba_1-ySr_y)Al₂Si₃O₄N₄:Eu²⁺was enhanced by replacing Ba²⁺ions with Sr²⁺.The relative strength of the phosphor at 473K which compare with room temperature?293K?still retain a high percentage,which indicates that the BASON:Eu²⁺phosphor has good thermal stability.In this experiment,we also mixed with commercial yellow phosphor YAG:Ce³⁺and red phosphor Sr₂Si₅N₈:Eu²⁺to abtain white LED.In addition,we doped Mn and Sm to obtain weak red luminescence and deep red wideband emission phosphors respectively,and studied their quenching mechanism and thermal stability in depth.Secondly,BaAl₂Si₃O₄N₄:Ce³⁺,Tb³⁺phosphors were synthesized by changing the doping of rare earth ions.Its luminescence properties were studied by means of X-ray diffraction and spectral characterization.The results of spectral analysis showed that Ce³⁺?Tb³⁺energy transfer existed in BaAl₂Si₃O₄N₄.By adjusting the doping concentration of Ce³⁺and Tb³⁺,BaAl₂Si₃O₄N₄:Ce³⁺and Tb³⁺phosphors were successfully regulated from blue light to green light by means of energy transfer.Thirdly,BaAl₂Si₃O₄N₄ broadband blue and yellow phosphors which doped with Ce³⁺and Yb²⁺were prepared.Its luminescence properties were studied by X-ray diffraction and spectral characterization.Under the irradiation of 254nm ultraviolet light,both phosphors showed long afterglow performance.The causes of the phenomenon were analyzed,and the sustainable time of the long afterglow was tested respectively.Fourth,a series of Eu²⁺doped(Ba_1-xCa_x)Al Si₅O₂N₇ and(Ba_0.7Ca_0.3)(Al_1-zy_z)Si₅O₂N₇ phosphors were prepared by high temperature solid phase method in reducing atmosphere.The crystallinity and luminescence intensity of samples can be increased by Ca²⁺substitution.According to the relationship between emission position and lattice environment,the different emission peaks in(Ba_1-xCa_x)Al Si₅O₂N₇phosphor can correspond to the sites which occupied by Eu²⁺respectively.Through the low temperature fluorescence thermal quenching test of(Ba_1-xCa_x)Al Si₅O₂N₇ phosphors,it was found that there was abnormal negative thermal quenching phenomenon,which means with the increase of temperature?from 4K to 273K?,the light intensity of phosphors showed enhanced continuity.The sample was also showed enhancement when tested at room temperature for high temperature heat quenching.With the add of Y³⁺,the long wavelength of(Ba_1-xCa_x)Al Si₅O₂N₇ can be broadened,which achieve the regulation from blue-green to orange-yellow.The warm white LED was successfully prepared by mixing(Ba_0.7Ca_0.3)Al Si₅O₂N₇:Eu²⁺phosphor and commercial red phosphor Sr₂Si₅N₈:Eu²⁺.