Preparation And Luminescent Properties Of Rare Earth Doped Gd₂（WO₄）₃Phosphors

Rare earth ions have rich energy can be excited from the ultraviolet to the infrared. Thephysical and chemical properties of it are stability.It is often used in light-emitting materials,especially rare earth doped nanostructured luminescent materials. Its performance isexcellent and has a broad application prospects. Preparation and room temperature emissionof nanocrystalline Gd₂（WO₄）₃：RE3+(RE=Eu³⁺、Eu³⁺-Sm³⁺、Er³⁺、Er³⁺-Yb³⁺) arestudied in this paper. The results and conclusions are as following:The nanocrystalline Gd₂（WO₄）₃doped by Eu³⁺,Eu³⁺/Sm³⁺,Er³⁺,Er³⁺/Yb³⁺are preparedby co-precipitation method in this paper. changing the doping concentration of the rareearth ion. The X-ray diffraction spectrum of the sample showed that the diffraction peak ofthe sample with the JCPDS card#23-1076matches the base-centered monoclinic structurecompletely. Calculated by the Debye-Scherrer equation （Debye-Scherrer） Gd₂（WO₄）₃:RE3+series of samples of the grain size of about40nm samples prepared nanoscaleparticles.Eu³⁺, Sm³⁺doped and codoped Gd₂（WO₄）₃nanocrystalline are prepared by chemicalco-precipitation method, respectively. When Eu³⁺is doped, the emission of5D0�'7F2is thegreatest. With the increase of doping concentration increased, When the mole fraction ofEu³⁺is20%, the luminescent intensity of Eu³⁺is the greatest. when the intensity of luminouscontinues to increase, the occurrence of the phenomenon of concentration quenching. Sm³⁺sensitized Eu³⁺in the samples Gd₂（WO₄）₃:Eu³⁺-Sm³⁺. The sensitized effect of Sm³⁺to Eu³⁺was more obvious when the sample Gd₂（WO₄）₃:Eu³⁺-Sm³⁺was excited by464nm light thanby395nm light. Doping Sm³⁺can realize the energy transfer from Sm³⁺to Eu³⁺, making theemission of5D0�'7F2more strength. When the mole fraction of Sm³⁺was5%, theluminescent intensity of Gd₂（WO₄）₃:Eu³⁺-Sm³⁺is the greatest,the light intensify will bedecreases when increasing. The transition of5D0�'7F2was clearly observed under405nm or440nm excitation. Therefore, Eu³⁺and Sm³⁺codoped in the matrix Gd₂（WO₄）₃greatlyexpanded the range of the wavelength of the excitation light source. The Er³⁺, Er³⁺/Yb³⁺doped nanocrystalline Gd₂（WO₄）₃phosphors are prepared byco-precipitation method. The down conversion characteristic emission from the trivalentrare earth Er³⁺ in the samples were observed. The concentration quenching will occur whenthe concentration of doped Er³⁺ exceeds3mol%. The up conversion characteristic emissionwere observed. When Eu³⁺is doped, The up conversion characteristic emission is not good,but, Er³⁺/Yb³⁺co-doped, up conversion emission intensity greatly enhanced, the resultsshow that Yb³⁺ion had a good sensitization for Er³⁺ ion up conversion emission. When thedoping concentration of Yb³⁺is1%, mainly2H11/2�'4I15/2level transition of Er³⁺4S3/2�'4I15/2level transition will be strengthened.When the Yb³⁺doping concentration graduallyincreasing, the level transition of4S3/2�'4I15/2is increased at the same time. Meanwhile thelaunching of Er³⁺/Yb³⁺co-doped upconversion green （540nm⁵63nm band） is a two-photon process.