Preparation And Luminescence Properties Of Rare Earth Ions Doped Ba-Al-Si-ON:Eu 2+ Nitrogen Oxide Green Phosphors

Due to the excellent properties such as lower energy consumption,higher efficiency,longer operation lifetime and environmental friendly,white light emitting diodes?LED?are considered as the fourth generation light source.Traditional green phosphors such as sulfides,phosphates and aluminates can not fulfill the requirements of LED devices because of their thermal stability.Rare earth ions doped oxynitrides have drawn much attention during the past years owing to the excellent luminous efficiency and thermal stability,the preparation of oxynitrides is usually quite difficult?i.e.extremely high temperature and high pressure?,which limits the application of oxynitrides.In this project,we aim to study on the preparation technology of oxynitrides under atmospheric pressure.A series of Eu²⁺ doped Ba_0.95Ln_xAl_1.4-xSi_0.6O_3.4N_0.6: Eu²⁺_0.05?Ln = Y,Gd,La,Lu?were successfully synthesized,the influence of synthesis condition and doping rare earth ions on luminescence properties were investigated.The following conclusions could be obtained from the investigation:?1?With the increase of Eu²⁺ concentration,the emission intensity increase for BaAl_1.4Si_0.6O_3.4N_0.6:Eu²⁺_x sample,the optimal doping concentration is found to be 5 mol %.The prepared phosphors can be excited in the wavelength range of 260-470 nm,matching well with the NUV and blue LED chip.Intense green emission can be observed under NUV and blue excitation,the color coordinates are?0.2752,0.6158?.?2?The influence of synthesis condition on the phase and luminescence of Ba_0.95YxAl_1.4-xSi_0.6O_3.4N_0.6:Eu²⁺_0.05 phosphors were investigated.The results showed that Ba₂SiO₄ is the main phase at 1100 °C,then BaAl₂O₄ gradually appears with the increase of temperature.The synthesis conditions were optimized to be 1200 °C and 6 h in our research.The key to the preparation of the green phosphor of oxynitrides is to select the proper reduction conditions,and the experiment results show that the ammonia gas is suitable to be used as the reduction atmosphere.The addition of proper flux can improve the luminous intensity of Ba_0.95YxAl_1.4-xSi_0.6O_3.4N_0.6: Eu2+ samples,BaF2 is the most effective flux in the present case.?3?To further improve the luminescence of Ba_0.95Al_1.4Si_0.6O_3.4N_0.6:Eu²⁺_0.05 phosphor,a series of Ba_0.95Ln_xAl_1.4-xSi_0.6O_3.4N_0.6: Eu²⁺_0.05?Ln = Y,Gd,La,Lu?phosphors were prepared.The synthesized phosphors show uniform distribution with average size in 2-10 ?m.The doping of Ln³⁺ ions did not significantly influence the crystal structure of the phosphor.The doping of Ln³⁺ ions can enhance the emission intensity to a certain extent,the optimal doping concentrations are 30 mol %,10 mol %,20 mol %,10 mol % for Y³⁺,Gd³⁺,La³⁺ and Lu³⁺ respectively.The relative emission intensities of Y³⁺,Gd³⁺,La³⁺ and Lu³⁺ doped phosphors are about 172 %,156 %,153 %,168 % of Ba_0.95Al_1.4Si_0.6O_3.4N_0.6:Eu²⁺_0.05 sample.All the sample show exponential decay,and the decay time is 467.56 ns.Temperature dependent luminescence were also investigated,the doping of Ln³⁺ can improve the thermal quenching properties,the relative emission intensity kept more than 75 % of their original intensity at 100 °C.