Study On Synthesis And Luminescence Properties Of BiOCl:Eu³⁺ Phosphor

Recently,it is very important to find a good red phosphor because the most widely used YAG:Ce³⁺phosphor is lack of red light.Halogen oxide is suitable for phosphor material because of its low phonon energy and high chemical stability.Especially BiOCl,as a kind of wide band gap semiconductor,due to its unique layers structure and more favorable substituted environment which provided by distinctive bonding between atoms for Eu³⁺ions.The trivalent Eu³⁺-activated phosphors exhibit good red light emission.Therefore,BiOCl:Eu³⁺is considered to be a potential red phosphor for white LED.In the present work,a red phosphor with high color index and good luminescence performance is expected to obtain.The BiOCl:Eu³⁺phosphors were obtained by co-precipitation,solid state reaction and hydrothermal method respectively.The samples were characterized via us ing X-ray diffractometer?XRD?,scanning electron microscope?SEM?,UV-Vis absorption spectra and photoluminescence spectrometer?PL?,respectively.In order to obtain the optimum conditions,the influence of two or more experiment factors was investigated.We also studied the influence of time,temperature,p H and concentration of Eu³⁺ions for BiOCl:Eu³⁺phosphor luminescence properties and structural characteristics.The main results are as follows.?1?The BiOCl:Eu³⁺phosphors were synthesized by three methods:co-precipitation,solid phase and hydrothermal method,respectively.NaOH solution of 6 mol/L was selected by experiment with urea,ammonia,sodium hydroxide of three kinds of precipitant respectively in different concentrations?0.5 mol/L,2 mol/L,6 mol/L,10 mol/L?.We found the optimum conditions in solid state method is 400?and 6h by studying luminescence properties of phosphors with different reaction temperature?200?/300?/400?/500??and different time?3h/6h/9h?.Hydrothermal method was investigated in detail by various temperature,time and p H,it is found that the optimum condition is160?,10h and p H=6.?2?By orthogonal experiment,the order of influencing the luminescence intens ity of each technological factor was clarified,and the evolution process of the particle morphology was explained by the Oster Wade ripening mechanism and self-assembly theory.The optimum condition of hydrothermal method was verified by orthogonal experiment,the influence of three factors on BiOCl:Eu³⁺phosphor luminescence intensity follows the sequence:time>p H>temperature,and the evolution process of particle morphology with time factors in hydrothermal experiment was studied.The result shows that with the prolonging of time?2h-12h?,the irregular flakes were arranged in order to form larger quadrilateral flakes,then,the quadrilateral flakes would stack orderly to form truncated octahedron-like particles.This process has involved Oster Wade ripening mechanism and self-assembly theory.?3?In order to obtain the red phosphors with high color and high efficiency,the Eu³⁺ions of different concentrations were used as activators.By analyzing emission spectra of different Eu³⁺ion doping concentrations,we found the main peak centered at 616nm under the excitation of 395nm.The emission intensity were improved with increase in Eu³⁺concentration,and then decreased for higher concentrations?above 5mol%?due to concentration quenching.Therefore,the best Eu³⁺doping concentration is 5mol%,the CIE color coordinates of?0.6329,0.3666?,the color purity of 86.7%,the quantum efficiency is 81.48%,indicating that the obtained sample is a potential red phosphor in WLED.?4?In order to further investigate the relevant information of the sample,Judd-Ofelt theory was employed to calculate the related parameters.The calculation showed that the present phosphors have a lower non radiative transition probability(A_N=127.12^S-1),lifetime??=1.457ms?and quantum efficiency??=81.48%?,This shows that the sample is a good red phosphor.Moreover,the BiOCl:Eu³⁺products with better stimulated emission cross-section??_e?and gain bandwidth(?_e×??_eff)which are suitable to apply in the field of optical display devices.