Study On Synthesis And Properties Of Eu³⁺ Doped Aluminate Phosphor With Excellent Thermal Stability

White light emitting diodes（WLEDs）are considered as semiconductor light-emitting devices still with great application potential.At present,commercial WLEDs are mainly composed of blue LED chips and Y₃Al₅O₁₂:Ce³⁺yellow phosphor.Due to the lack of red component in the practical application of the WLEDs,there are some problems such as high color temperature and low color rendering index,which limit the application of the WLEDs.Another kind of WLEDs combining red,green and blue（RGB）phosphors with near-ultraviolet LED chips have attracted people’s attention.By adjusting the ratio of colored phosphors,higher quality white light can be obtained.In addition,when the surface temperature of the device is too high,the luminescence of the phosphors is often quench and the luminescence efficiency of the WLEDs decreases.Therefore,it is of great significance to study red phosphors with high thermal stability for high quality applications of WLEDs.In this paper,we selected Eu³⁺doped aluminate-based materials as research objects,and synthesized three series of near-UV excited red phosphors with high thermal stability.The main innovations and achievements are as follows:1.Ca Al₄O₇:Eu³⁺red-emitting phosphors were prepared by sol-gel method,and novel Ca Al₄O₇:Eu³⁺,B³⁺/Na⁺/Mg²⁺phosphors were synthesized by doping B³⁺,Na⁺and Mg²⁺ions,respectively.（1）For the first time,Ca Al₄O₇:Eu³⁺phosphors were found to have negative thermal quenching,and the integrated fluorescence intensity at 90℃is 1.27 times of the initial value at 30℃.（2）The fluorescence intensity of Ca Al₄O₇:Eu³⁺doped with B³⁺at room temperature is1.45 times that of the original Ca Al₄O₇:Eu³⁺.The optimum luminescence temperature was increased to 170℃,and the corresponding integrated fluorescence intensity was 1.41 times of the initial value at 30℃.（3）The fluorescence intensity of Ca Al₄O₇:Eu³⁺doped with Na⁺at room temperature is1.81 times that of the original Ca Al₄O₇:Eu³⁺.The optimum luminescence temperature was increased to 170℃,and the corresponding integrated fluorescence intensity was 1.65 times of the initial value at 30℃.（4）The fluorescence intensity of Ca Al₄O₇:Eu³⁺doped Mg²⁺at room temperature is 1.67times that of the original Ca Al₄O₇:Eu³⁺.The optimum luminescence temperature was increased to 250℃,and the corresponding integrated fluorescence intensity was 2.28 times of the initial value at 30℃.2.Sr La Al O₄:Eu³⁺red-emitting phosphors were prepared by sol-gel method,and novel Sr La Al O₄:Eu³⁺,Ca²⁺/Na⁺phosphors were synthesized by doping Ca²⁺,Na⁺ions,respectively.The luminescence of Sr La Al O₄:Eu³⁺is normal thermal quenching.The Co-doping of Ca²⁺and Na⁺not only enhances the luminescence intensity of Sr La Al O₄:Eu³⁺phosphor,but also turns normal thermal quenching to negative thermal quenching:（1）The fluorescence intensity of Sr La Al O₄:Eu³⁺doped with Ca²⁺is 1.92 times of that of Sr La Al O₄:Eu³⁺at room temperature.The optimum luminescence temperature was increased to 90℃,and the corresponding integrated fluorescence intensity was 1.01 times of the initial value at 30℃.（2）The fluorescence intensity of Sr La Al O₄:Eu³⁺doped with Na⁺is 1.31times of that of Sr La Al O₄:Eu³⁺at room temperature.The optimum luminescence temperature was increased to 150℃,and the corresponding integrated fluorescence intensity was 1.33 times of the initial value at 30℃.3.Gd₄Al₂O₉:Eu³⁺red-emitting phosphors were prepared by sol-gel method,and novel Gd₄Al₂O₉:Eu³⁺,Bi³⁺phosphors were synthesized by doping Ca²⁺,Na⁺ions.（1）For the first time,the luminescence of Gd₄Al₂O₉:Eu³⁺phosphors were found to have a negative thermal quenching phenomenon.Under the variable temperature test,the optimal luminescence temperature is 120℃,and the corresponding integrated fluorescence intensity is 1.83 times of the initial value at 30℃.（2）Doping Bi³⁺can effectively improve the fluorescence intensity.Under the excitation light of 316 nm and 392 nm,the fluorescence intensity of Gd₄Al₂O₉:Eu³⁺and Bi³⁺at room temperature is 2.57 and 1.72 times that of the original Gd₄Al₂O₉:Eu³⁺,respectively.（3）Due to the high sensitivity of Bi³⁺to temperature changes,the thermal stability of Gd₄Al₂O₉:Eu³⁺,Bi³⁺is weaker than Gd₄Al₂O₉:Eu³⁺,but the fluorescence intensity at 150℃is still greater than the initial intensity at 30℃.