Preparation And Luminescent Properties Of YVO₄?X=Nb,V,Ta?

Rare earth elements have 4f outer layer electrical structure,so they have special electronic,chemical and optical properties,and have a very wide range of applications in the optoelectronic industry.Rare earth elements can be used as matrix components,activator,CO activator,sensitizer or dopant of fluorescent materials.The composite oxides of transition metals V,Nb and Ta are important matrix materials.This paper focuses on the preparation of several rare earth vanadate,rare earth niobate and rare earth tantalate,studies their molecular structure and luminescent properties,and obtains the following main research results.A series of YNb_1-xO₄:x V samples were prepared by high temperature solid state method.Materials with different structures were obtained by continuously changing the concentration of Nb and V.The X-ray powder diffractometer was used to characterize the structure of the samples.It was proved that the obtained phosphors have two crystal structures:Zircon structure and niobium yttrium Brown structure.The luminescent properties of phosphors were studied by fluorescence spectrum.It was found that the luminescent properties of VO₄^3-group and Nb O₄^3-group were about 420 nm and 400 nm respectively.However,the effect of a small amount of V⁵⁺doping in ynbo4 and a small amount of Nb⁵⁺doping in YVO₄on the luminescence is obviously different.Through the continuous change of the ratio of V and Nb,its luminous properties can not continuously change from one kind of luminescence to another,but reach the lowest at a certain composition.The results show that there are two mechanisms of luminescence quenching.A series of YTa_1-xO₄:x Nb samples were prepared by high temperature solid state method.Materials with different structures are obtained by continuously changing the concentration of Ta and Nb.The structure of the sample was characterized by X-ray powder diffractometer.It was proved that the phosphor obtained was YTa O₄of M'type and YNb O₄with the crystal structure of niobate.It is found that the luminescence of the Ta O₄^3-group and Nb O₄^3-group are about 330 nm and 400 nm respectively.In this paper,the structure,composition and luminescent properties of the compounds were studied.With the increasing concentration of Nb O₄^3-group in tantalate,the structure of the compounds changed from M'YTa O₄to YNb O₄,and the luminescent properties of the compounds changed accordingly.A new luminescent material Y_0.98Sm_0.02Ta_1-xNb_xO₄was synthesized by high temperature solid state method.The structure of the sample was characterized by X-ray powder diffractometer,and it was proved that the crystal structure was not changed by doping ions.The excitation energy can be transferred to Sm³⁺through Nb O₄^3-group.With the increase of Nb O₄^3-group concentration in tantalate,the structure of the compound changes from M-type YTa O₄to yttrium niobium type YNb O₄,and its luminescent properties change accordingly.When the concentration of Nb⁵⁺x=0.2,the luminescent intensity of the sample reaches the maximum under 257 nm excitation,and when the concentration of Nb⁵⁺x=0.995,the luminescent intensity reaches the maximum under405 nm excitation.The fluorescence lifetime of the sample decreases with the increase of Nb⁵⁺,which proves the phenomenon of energy transfer between Sm³⁺.The samples of Y_0.98Sm_0.02Ta_1-xNb_xO₄?x=0?0.05?also showed afterglow properties.