Synthesis And Luminescence Properties Investigation Of Rare Earths Doped Niobate Phosphors

In the past years,luminescent phosphors materials have been widely applied in the fields of solid state lighting and display,such as light-emitting diodes,signal indicator lights,instrum display,and urban road lighting.Particularly,white light-emitting-diodes?LEDs?have received close concern due to their superior features such as high luminescence efficiency and low power consumption.At present,there are two main ways to fabricate the white lights.One is to combinate the yellow-emitting Y₃Al₅O₁₂:Ce³⁺?YAG?phosphors with blue InGaN chip,the other is to pump three RGB-emitting?red,green and blue?phosphors with near ultraviolet LEDs,and the later approach is been widely used nowadays.Generally speaking,the luminescence efficiency of the materials is confined by the doping concentration,the surrounding crystal fields and energy transfer characteristics between the host and the doped rare earths?activator?,and so on.Therefore,selecting an appropriate and feasible host lattice of the RE ions is very important and necessary.Niobates,tantalates and tungstates belong to family of inorganic compounds have already been widely investigated and applied in phosphors applications.Lots of results showed that niobates have excellent thermal and chemical stability and also good performance in piezoelectric and nonlinear matrix,so that niobates are an important kind of light-activated host materials.The purpose of this paper is to develop novel tricolor?red,green and blue?phosphors in niobate host which excited by the UV-LED chip.In this paper,the traditional solid-state reaction method has been used to fabricate the w-LEDs phosphors,and the phase composition,energy transfer and luminescence properties were investigated in detail.?1?A series of Na_2-xNbAlO₅:xLn³⁺?Ln=Sm/Eu?phosphors have been synthesized through conventional solid-state reaction method.The energy transfer mechanisms,thermal stabilityand photoluminescence of Na_2-xNbAl O₅:x Ln³⁺?Ln=Sm/Eu?phosphors have also been discussed.Under the ultraviolet excitation,the samples exhibited orange(Sm³⁺)and red(Eu³⁺)emission and the system of Na_2-xNbAlO₅:xLn³⁺?Ln=Sm/Eu?phosphors also have excellent thermal stability.?2?A color-tunable phosphor based on Na_2-xNbAlO₅:xLn³⁺?Ln=Dy/Er?were synthesized by a traditional solid-state reaction method.X-ray powder diffraction?XRD?,diffuse reflectance spectra,photoluminescence spectra and decay curves were utilized to characterize the as-prepared phosphors.We adjusted component of Dy³⁺/Eu³⁺to control the emission color.The color tone of the Na_2-xNbAlO₅:xDy³⁺samples can be changed from cyan through white region and eventually to green-white region,which imply that the obtained Na₂NbAlO₅-host phosphors system may have potential applications as novel materials in ultraviolet pumped w-LEDs and light-emitting display fields.?3?A series of Sr_5-xNb₄O₁₅:xEu³⁺phosphors were prepared via the high temperature solid-state reactionmethod.The photoluminescence properties and concentration quenching mechanism have been analyzed and discussed.Under 393nm excitation,the color tone can be changed from orange-red region to red region with the change of Eu³⁺concentrations.And the concentration quenching mechanism of Eu³⁺in Sr_5-xNb₄O₁₅ host is quadrupole-quadrupole?q-q?interaction.