Synthesis And Properties Of Rare Earth Ion Doped Ba₃Y₄O₉ Fluorescent Materials

In this paper,a series of Ba₃Y_?4-4x-4y?Eu_4xGd_4yO₉?x=0?0.01?0.03?0.05?0.07?0.09,y=0?0.05?0.10?0.15?0.20?0.25?0.30?phosphors were synthesized by solid phase method,sol-gel method and coprecipitation method,respectively.through the comparison of calcination temperature,it was determined that the best synthesis method of the system was ammonium bicarbonate homogeneous precipitation method.Using this method,a series of phosphors were synthesized by adjusting the content of different element ions.The phase structure,micro-morphology and optical properties of the samples were analyzed by means of FT-IR,XRD,TGA/DSC,FE-SEM,PLE/PL and fluorescence attenuation analysis.the main results are as follows.The mother salt solution was mixed with Gd?NO₃?₃ and Eu?NO₃?₃,Ba?NO₃?₂ was added,NH₄HCO₃ was used as precipitant,and the precursor was synthesized by coprecipitation method.Ba₃Y_?4-4x-4y?Eu_4xGd_4yO₉ phosphors were synthesized after calcination at 1400^oC for 5h.Fourier transform infrared analysis shows that all precursors have similar functional groups,and the chemical formula of the precursors is?NH₄?_xBa₃RE₄?OH?_y?CO₃?_z·nH₂O(RE³⁺=Y³⁺,Gd³⁺,Eu³⁺),which is completely decomposed into oxides at 1200°C.FE-SEM tests show that the particle size of the precursor of the system is in the range of 50nm?100nm.After calcination,the particles grow and disperse well,with a particle size of 1nm?2?m;the calcined product is Ba3?Y,Eu,Gd?4O9 solid solution,and it is determined that the pure phase cannot be maintained when the doping concentration of Gd³⁺is more than 10%;diffuse reflectance tests show that the light absorption capacity of Ba₃Y_?4-4x-4y?Eu_4xGd_4yO₉ system phosphors increases with the increase of doping ion concentration.The optimum doping concentration of Ba₃Y_?3.6-4x?Eu_4xx Gd_0.4O₉,Eu³⁺is 0.05 by PLE/PL spectroscopy,and the quenching mechanism is the interaction between rare earth ions.Under the monitoring of258nm wavelength,the ⁵D₀-⁷F₂ transition of Eu³⁺occurs at 615nm,showing excellent red light emission;the quantum yield of Ba₃Y_3.4Eu_0.2.2 Gd_0.4O₉ is up to 24%;the quenching concentration of the system is 5%,and the quenching type is the energy exchange mechanism between rare earth ions.The fluorescence lifetime of Ba₃Y_3.4Eu_0.2.2 Gd_0.4O₉ phosphor at 615nm is?1.763ms,by single exponential function fitting.The fluorescence lifetime of Ba₃Y_3.8Eu_0.2O₉ system is?1.22ms.The introduction of Gd element has little effect on the lifetime of the phosphor.The encapsulated luminaire shows orange-red light emission,and the calculated position within the color coordinates?0.64,0.36?,and also shows excellent orange-red light emission under the UV lamp.Ba₃Lu_?4-4x?Eu_4xO₉ and Ba₃Sc_?4-4x?Eu_4xO₉ phosphors were successfully prepared by coprecipitation method.The particle sizes and morphologies of the phosphors of Ba₃Y_?4-4x-4y?Eu_4xGd_4yO₉ system are similar to those of the precursor and calcined products.Among many samples,the luminous intensity of Ba₃Y_3.4Eu_0.2Gd_0.4O₉ phosphor is the strongest,Ba₃Sc_3.8Eu_0.2O₉ is the second,and Ba₃Lu_3.8Eu_0.2O₉ phosphor is the weakest,which is mainly due to the energy transfer process of Gd³⁺?Eu³⁺.A series of Ba₃Y_?4-4x-4y?Er_4xYb_4yO₉ upconversion phosphors were synthesized by co-precipitation method.The chemical formula of its precursor is?NH4?_x Ba3RE4?OH?_y?CO₃?_z·nH₂O(RE³⁺=Y³⁺?Er³⁺?Yb³⁺).The particle size of the precursor is between 50nm and100nm,and the particle size of the calcined product is between 1nm and 2?m.Through the diffuse reflectance test,it is known that the light absorption capacity of the fluorescent materials of the system is enhanced with the increase of doping ions.The optimum doping amount of Ba₃Y_?4-4x-4y?Er_4xYb_4yO₉ co-doped with Yb³⁺/Er³⁺is 0.05 and 0.20,respectively.Under 978 nm laser excitation,Yb³⁺transfers the absorbed energy nonradiantly to Er³⁺,and excitates Er³⁺electrons from the ground state ⁴I_15/25/2 to the ⁴I_11/21/2 level.The electrons at the ⁴I_11/2level are further excited to the ⁴F_7/2/2 level by energy reabsorption.The electrons at the ⁴F_7/2level can transition to the excited states of ²H_11/2,⁴S_3/2/2 and ⁴F_9/2/2 through non-radiative transition,and finally return to the ground state ⁴I_15/25/2 through radiative transition and produce upconversion luminescence at 535,558 and 665 nm.The fluorescence lifetime of Ba₃Y₃Er_0.2Yb_0.8O₉ is 54.86±3.56?s,and the fluorescence lifetime of the system decreases with the increase of Yb³⁺content,first decreases and then increases slightly with the increase of Er³⁺content.The color coordinate of the phosphor of Ba₃Y₃Er_0.2Yb_0.8O₉ is?0.73,0.27?,and the color temperature is 7383.6 K,showing excellent red light emission.