Preparation And Luminescence Properties Of Eu/Tb Doped Borosilicate Fluorescence Glass For White LED

White LED?W-LED?have been widely used in the fields of illumination,display and car headlights due to the advantage of energy saving and environmental protection.However,the main commercial W-LED prepared by conventional phosphor coating process still have some defects in color rendering and thermal stability owing to short of red light and organic packaging of phosphor,which seriously limits their further application and development.Some studies show that borosilicate glass as a matrix has good rare earth solubility,and the activators of Eu²⁺,Tb³⁺,Eu³⁺have strong absorption and luminescence properties under near-ultraviolet or violet excitation.It is one of the effective ways to overcome its drawbacks by preparing rare earth doped fluorescence glass.In this paper,preparation and luminescence properties of Eu doped and Eu/Tb co-doped borosilicate glass were studied for W-LED.The luminescence of Eu²⁺,Eu³⁺and self-reduction mechanism of Eu³⁺?Eu²⁺were systematically studied by varying alkaline earth metal and glass composition under air conditions.The structure and luminescence properties of glasses under the conditions of complete and partial carbon reduction were investigated.The white light emission and light color adjustment of Eu,Tb co-doped borosilicate glass were discussed.The contents and results are as follows:?1?In the air conditions,Eu ion doped aluminoborosilicate glass containing different alkaline earth metal oxides:Al₂O₃–B₂O₃–SiO₂–Eu₂O₃–MO?M=Mg,Ca,Sr,Ba?was prepared by melt-cooling method.Under the excitation at 365 nm,the blue emission at 469 nm and the red emission at 615 nm respectively correspond to the 5d?4f transition of Eu²⁺and the⁵D₀?⁷F₂ transition of Eu³⁺.Among them,the Eu²⁺luminescence intensity in the glass containing SrO is the strongest,indicating the Eu³⁺?Eu²⁺has a strong degree of self-reduction.The characteristic emission of Eu²⁺and Eu³⁺behave stronger in the glass with composition of 30SiO₂–40B₂O₃–30SrO.It is resulted that the tetrahedral network structure such as[BO₄],[AlO₄],[SiO₄]in the glass structure,which have a shielding effect on Eu²⁺.Under the excitation of near-ultraviolet light,the emission white light composed with blue light and red light locates in the white-light reddish area.?2?In the condition of complete carbon reduction,the borosilicate glass with different Eu²⁺concentrations were prepared based on the above glass matrix composition.As the concentration of Eu²⁺increasing,the density first rises and then decreases,the molar volume goes up first and then declines,and the absorption intensities gradually enhance and show red shift,the optical band gap E_g gradually decreases,and a weak red shift in excitation and emission.0.4 mol%Eu²⁺is optimal doping concentration.The largest tightness of glass network structure and strongest blue light emission of Eu²⁺are obtained under the condition of 0.4 mol%Eu²⁺doping concentration.It is showed adjustable luminescence to a certain extent under excitations of different wavelength.The energy transfer between Eu²⁺–Eu²⁺increases and luminescence intensity decreases with increasing measure temperature in temperature dependent spectrum.The thermal quenching activation energy is 0.26 eV.The glass structure is amorphous and the glass transition temperature is 455?,the crystallization temperature is 810?,which indicates it has a good thermal stability.?3?In the condition of partial carbon reduction,the strontium borosilicate glass doped with 0.6 mol%Eu₂O₃ was prepared.When the carbon sequestration is controlled at 25wt%,the sample emits white light at 365 nm excitation with the color coordinates of?0.3632,0.324?and correlated color temperature of 4154.4 K.The strontium borosilicate glass doped with Tb³⁺was prepared.The glass can effectively supplement green light component.It is resulted from Tb³⁺is excited at 378 nm violet light?corresponding to ⁷F₆?⁵D₃ transition?and emits543 nm green light?corresponding to ⁵D₄?⁷F₅ transition?.The single matrix strontium borosilicate glass co-doped with Eu,Tb was prepared.Eu²⁺-Tb³⁺-Eu³⁺coexist in the glass.The glass achieves superiors white light emission and shows adjustable color under excitation of 365 nm.The strontium borosilicate glass owns optimal overall performance of white light co-doped with 0.6 mol%Eu and 0.5mol%Tb.The fluorescence lifetime indicates that Eu²⁺?Tb³⁺?Eu³⁺energy transfer occurs between rare earth ions.