Investigation On The Preparation And Performance Of The New Double Perovskite Phosphors

Due to the advantages such as the small size,long lifetime,low energy consumption,fast response and so on,white emitting light diode?WLED?is considered as a new generation of light source to replace the traditional incandescent and fluorescent lamps.At present,the main way to obtain white light by WLED is phosphor conversion method.The near-UV LED chip match with three primary colors or single phosphor has become a hot spot.Tungstomolybdate is considered to be an important optical material due to its good physicochemical properties,thermal stability and strong absorption to near-ultraviolet light.Double perovskite composite oxides can provide a rich and varied combination of elements,making it a research object of great academic value.In this paper,we successfully prepared a series of fluorophores with double perovskite structure as matrix and various rare earth ions as activators by using sol-gel method with EDTA-citric acid as double complexing agent powder material.The Sr₂CaWO₆:RE³⁺?RE=Dy,Sm,Eu?phosphors prepared by the sol-gel method exhibit anomalous magnetic dipole transition emission.The Rietveld refinement of the XRD patterns and DFT calculations verify the as-prepared Sr₂CaWO₆ phosphors crystallize in the monoclinic structure of the P2₁/n space group instead of the Pmm2 space group with the orthorhombic structure.The exact electronic structure of Sr₂CaWO₆ was obtained using the HSE06 hybrid functional and confirmed that Sr₂CaWO₆ is an indirect bandgap semiconductor with a bandgap of 4.24 eV,which is 0.73 eV higher than the experimental results.The valence band maximum of Sr₂CaWO₆ is mainly contributed by the 2p electronic state of O,and the conduction band minimum is mainly contributed by the 5d electronic state of W.The as-prepared Sr₂CaWO₆:RE³⁺phosphors showed a strong charge transfer band in near-ultraviolet region,which is much strong than that of characteristic excitation peak of the doped rare earth ions.Thus,the effective energy thansfer occurred between the matrix and activator ions.The luminescence intensity was enhanced with the charge compensation agent.The near white light emission of Sr₂CaWO₆:Sm³⁺phosphor can be achieved under near UV excitation with CIE color coordinates?0.36,0.30?.In addition,the sample of Sr₂CaWO₆ treated under a reducing atmosphere is a photocatalytic material that responds to near ultraviolet light.A series of Sr₂CaMoO₆:RE³⁺?RE=Sm,Eu?and Sr₂ZnWO₆:RE³⁺?RE=Dy,Sm,Eu?were also prepared by the sol-gel method.The near-white light output of the Sr₂CaMoO₆:Sm³⁺and Sr₂ZnWO₆:Dy³⁺phosphors were achieved under 370 nm and 290 nm excition,respectively.The color coordinates is calculated to be?0.348,0.325?and?0.327,0.375?,respectively,which means that they are the potential phosphors for WLED.