Study On Structural And Photoluminescent Properties Of The Eu-doped Rare Earth Sesquioxides Hollow Spheres

Eu³⁺-doped rare earth sesquioxides(RE2O3: Eu³⁺),as a class of most important red phosphors,have a simple composition,better thermal stability,reduced outgassing,and were widely used in light emitting and display areas.RE2O3: Eu³⁺ phosphors were classically made via solid state reaction,then reduce the phosphors to micrometer size by milling.However,the process induces high populations of lattice defects and hence lower the luminosity and broadens the emission peak.In the paper,uniform RE2O3: Eu³⁺?RE= Y,Gd?phosphors were successfully prepared via a urea-based homogeneous precipitation technology with colloidal melamine formaldehyde?MF?microspheres as templates and lanthanide nitrate?Yttrium nitrate or Gadolinium nitrate?as row materials,followed by a subsequent calcination process.Phosphors prepared by this method will completely overcome the defects brought by the milling process.In the paper,effect of Eu³⁺ contents on the lattice constant and photoluminescent properties of the RE2O3?RE=Y,Gd?hollow microspheres were studied.Subsequently,the influence of the calcined temperature on the crystal size and photoluminescent properties of the optimum Eu-doped RE2O3?RE=Y,Gd?hollow microspheres were studied.For improving luminescence,co-doped the optimum Eu-doped Y₂O₃ phosphors with Gadolinium.Also,effect of the Gd contents and the calcined temperature on the crystal structure and photoluminescent properties of the co-doped hollow microspheres were studied.The hollow microspheres were characterized by scanning electron microscope?SEM?equipped with energy-dispersive X-ray spectrum?EDS?,transmission electron microscopy?TEM?,Fourier transform infrared spectroscopy?FTIR?,X-ray diffractometer?XRD?,photoluminescence spectrophotometer.The main results are as follows:?1?Uniform Y₂O₃: Eu³⁺ red-phosphor hollow microspheres with a smooth and dense surface were synthesized by fixing the Ytterbium nitrate at 0.8mmol and changing the amount of the Europium nitrate.Within the scope of the study,the lattice constant of theY₂O₃: Eu³⁺ hollow microspheres increase with the Eu³⁺ contents increasing.The phosphors show intense red emission at 613 nm,with optimum contents at 5%.The phosphors had a Bixbyite structure and crystal size increase with temperature increasing.The photoluminescence became more and more intense with the temperature increasing.?2?Monodispersed Gd₂O₃: Eu³⁺ red phosphors with a hollow structure and a smooth and dense surface were obtained by by fixing the Gadolinium nitrate at 0.8mmol and changing the usage of the Europium nitrate.Within the scope of the study,the lattice constant of the Gd₂O₃: Eu³⁺ hollow microspheres show a linear increase with the Eu³⁺contents increasing.The phosphors show intense red emission at 613 nm,with optimum contents at 5%.Then,effect of temperature on the crystal size and photoluminescent properties of the Gd₂O₃: 5%Eu³⁺ sample were studied.The phosphors had a Bixbyite structure and crystal size increase with temperature increasing.The photoluminescence became more and more intense with the temperature increasing.?3?A narrow size distribution with a smooth and dense surface of Europium and Gadolinium co-doped Yttria hollow microspheres were obtained by fixing Europium nitrate at 0.04 mmol and changing the relative amount of Yttrium nitrate and Gadolinium nitrate?while nGd+nY=0.8mmol?.Within the scope of the study,Yttria and Gadolinia forms a continuous solid solution,the lattice constant of the co-doped samples increases linearly with the Gadolinium increasing.Gadolinium had no effects on the emission profile and position of the co-doped samples.The most intense emission was obtained with the ratio of Gadolinium to Yttrium being 1:1.The crystal size increases with the temperature increasing,as well as the photoluminescence.