Preparation And Luminescence Of Eu-doped BMN Composite Perovskite

Rare earth luminescent materials have high fluorescence quantum efficiency,large stokes shift and long-term optical stability.Ba(Mg_1/3Nb_2/3)O₃?BMN?is a composite perovskite oxide with high tolerance,various lattice sites and good chemical stability,and have a band gap absorption in the ultraviolet band.BMN can provide suitable crystal environment and transfer energy for rare earth ions.In this paper,Eu³⁺was used as doped ions to prepare down-conversion fluorescent materials with broad spectrum absorption and high red-light color purity.Their structure and luminescence performance have been studied,and the influence of charge compensator and sensitizer on their structure and luminescence performance also have been discussed.?1?BMN:Eu phosphors were prepared by wet chemical method.According to XRD,Raman analysis and luminescent properties,BMN:Eu was hexagonal structure with 1:2 ordered B-site ions,and Eu³⁺replaced Ba²⁺and occupied the 2d site with C_3vv point symmetry.BMN:Eu phosphors have a wide excitation band around 280-360 nm,which is derived from the charge transfer transition between Nb-O of BMN host,and it broadens the excitation range of Eu³⁺.Under the excitation of near-ultraviolet light,BMN:Eu phosphor had the strongest emission peak of electric dipole transition ⁵D₀-⁷F₂ at 615 nm,indicating that Eu³⁺occupied the non-inversion center site.The optimal doping concentration of BMN:Eu phosphor powder was 3 mol%,and the critical quenching distance was 16.31?.The CIE color coordinate of BMN:3%Eu was?0.656,0.344?,indicating it had high red-light purity and was potential as a red phosphor.The fluorescence lifetime of BMN:3%Eu fluorescent powder was about 1.34ms,and the quantum efficiency was about 77.26%.BMN:Eu fluorescent thin films,which are transparent to near ultraviolet and visible light,were prepared by spin coating method.?2?BMN:3%Eu phosphors were doped with charge compensators?Li⁺,Na⁺,K⁺?and the effect on their structure and luminescence performance were studied.The luminescence properties of BMN:Eu,K phosphors was similar to that of BMN:Eu phosphors.With the increase of K⁺doping concentration,the luminescent intensity of BMN:3%Eu,x%K phosphors gradually increased,reaching the maximum value at x=3,about 55%stronger than that without K⁺doping.Among different charge compensators,Na⁺had the best enhancement effect on phosphors,followed by Li⁺,and K⁺had the weakest effect,which may be attributed to lattice distortion due to different substituting ion radii.The charge compensator shortens the lifetime of phosphors,and increases the intensity ratio of red light to orange light.The charge compensator improved the luminescent properties of BMN:Eu in various aspects.?3?BMN:Dy phosphor was prepared by wet chemical method,and its structure and luminescence properties were studied.BMN:Dy phosphor could emit blue light at490 nm and yellow light at 584 nm under the ultraviolet excitation light of 368 nm,which was originated from magnetic dipole transition ⁴F_9/2-⁶H_15/2 and electric dipole transition ⁴F_9/2-⁶H_13/2,respectively,and they had good down-conversion luminescence properties.The intensity of blue light at 490 nm was greater than that of yellow light at584 nm,indicating that Dy³⁺occupied the inversion center site instead of Ba²⁺occupying the 1a site,and had D_3d point symmetry.?4?The luminescent properties of Eu³⁺and Dy³⁺doped BMN phosphors were studied.The phosphors have both luminescent properties of Eu³⁺and Dy³⁺.Monitored under the light of Eu³⁺at 615 nm,the UV excitation peaks of Eu³⁺and Dy³⁺could be observed at the same time,indicating that there was energy transfer from Dy³⁺to Eu³⁺,which made the phosphors have a wider excitation range.Under excitation light at 365nm,the phosphors could emit blue,yellow light of Dy³⁺and red light of Eu³⁺.When the concentration of Dy³⁺was fixed,with increasing Eu³⁺doping concentration,the luminescent intensity of Dy³⁺gradually became weaker and the lifetime shortened because of the energy transfer.The mechanism of energy transfer was electric-electric dipole interaction.Meanwhile,The luminescent colors of phosphors changed from green to white to orange-red,and by adjusting the concentration of Eu³⁺,Dy³⁺,white light emission could be realized.