Preparation,Structure And Effective Approach To Enhance Luminescence Of Rare Earth Eu³⁺-Doped Lanthanum Molybdate Tungstate

In recent years,the continuous development of white light emitting diodes?LEDs?has replaced traditional incandescent and fluorescent lamps.As a new generation of solid-state lighting,white LEDs have the advantages of long life,small size,superior energy saving effect,high conversion efficiency,no mercury pollutionand other merits.The most common way to obtain white LEDs is the phosphor conversion method.However,there is a lack of efficient near-ultraviolet or blue-light excitedred phosphors.It is necessary to develop more novel and effective red light-emitting phosphor materials to improve the color rendering index of white LEDs.In this paper,a series of red phosphors La_2-xMo_yW_2-yO₉:xEu³⁺were prepared by using a solution combustion method with lanthanum molybdate tungstate as the host material and doped with rare earth Eu³⁺ions.It was found that when the phosphor samples were in different x and y value,the host materials may show different structures but they could be effectively excited with blue light.By adding suitable surfactants to modify the phosphors,the fluorescence intensity of the samples can be enhanced.In order to analyze the the influence of concentration of doped rare earth Eu³⁺ions,the calcination temperature,the optimal molar ratio of Mo and W,and different surfactants on the properties of the phosphors,the samples were characterized by X-ray diffraction?XRD?,scanning electron microscopy?SEM?,energy spectroscopy?EDS?,excitation and emission spectra,and quantum yield.The results show that in the calcination temperature range explored in this paper,the concentration of rare earth Eu³⁺ions and the molar ratio of Mo to W have an effect on the structure of the sample.But when Mo is added to the sample,the change of Eu³⁺concentration cannot change the structure of the sample.This shows that Mo is dominant in changing the sample structure.Under the excitation of 464 nm blue light,all samples show the characteristic red emission of Eu³⁺.The optimal concentration of doping Eu³⁺?x=0.8?and the molar ratio of Mo and W?1:1?were determined.Moreover,the addition of suitable amount of surfactant not only can improve the crystallization effect of the sample,but also greatly enhances the luminescence and quantum efficiencies.The effect of different surfactants on the sample is slightly different.The study on the preparation of surfactant-modified lanthum molybdate tungstate phosphors doped with rare earth Eu³⁺ions by solution combustion method is beneficial to improve the color rendering index in white LEDs,and provide a favorable basis for the design and development of red phosphors with high-quality.