Synthesis And Properties Of Rare Earth Doped Rare-earth-rich Phosphate Materials

Rare earth-rich phosphate materials?Y₃PO₇?La₃PO₇ Gd₃PO₇?were prepared by co-precipitation method and/or polyacrylamide gel process.The X-ray diffraction?XRD?,Fourier transform infrared spectroscopy?FT-IR?,Scanning electron microscopy?SEM?and Photoluminescence spectroscopy?PL?were used to investigated the phase structures and optical properties of the as-synthesized samples.The effects of synthetic conditions on the phase structures and optical properties of the as-synthesized samples were analyzed.The Tb³⁺doped Y₃PO₇ phosphors were synthesized by co-precipitation method.The influences of the pH,the pH regulators and the doping concentration of Tb³⁺on the phase structures,and luminescence properties of the synthetic Tb³⁺doped Y₃PO₇samples were investigated.The results show that the pure phase Tb³⁺doped Y₃PO₇crystals with monoclinic structure can be synthesized when the pH is 6.7.The Y₃PO₇:Tb³⁺crystals with high crystallinity and excellent photoluminescence properties can be prepared when the pH adjusted to 6.7 with Na₂CO₃ solution.The Y₃PO₇:Tb³⁺samples can be effectively excited by 255 nm ultraviolet light and emit bright characteristic green light of Tb³⁺ions.And the Tb³⁺doped Y₃PO₇ sample with the doping amount of8.at%displays the strongest luminescent intensity than that with other doping contents.The Eu³⁺doped Gd₃PO₇ crystals were synthesized by co-precipitation technique.The influences of the pH,the calcination temperature,the mole ratio of RE?RE=Gd and Eu?to P?n?Gd+Eu?/n?P??,and the doping concentration of Eu³⁺on the phase structures,luminescence properties of the as-synthesized Eu³⁺doped Gd₃PO₇ samples were investigated.The results show that the optimum synthesis conditions can be summarized as follows:the pH of the solution is 6.7,the calcination temperature is 900^oC,the calcination time is 25 h,the mole ratio of RE?RE=Gd and Eu?to P?n?Gd+Eu?/n?P??is 4:1.The as-obtained Gd₃PO₇:Eu³⁺samples can be effectively excited by276 nm ultraviolet light and emit bright characteristic red light of Eu³⁺ions.The photoluminescence spectra show the strongest emission peak located at 619 nm indicating that the dominant transition mode of Eu³⁺is electric dipole transition?⁵D₀-⁷F₂?,and confirming that Eu³⁺is ions are located in the non-inversion symmetry site in the lattice.The concentration quenching phenomenon can be observed when the doping content is above 20 at%.The Eu³⁺doped La₃PO₇ crystals were successfully synthesized via co-precipitation routes or polyacrylamide gel process.The influences of the pH of the solution and the calcination time on the phase structures,and luminescence properties of the as-synthesized Eu³⁺doped La₃PO₇ samples were investigated.The results reveal that the Eu³⁺doped La₃PO₇ crystals with monoclinic structure can be prepared by all the two method?co-precipitation method and polyacrylamide gel mothod?.The optimum synthesis conditions for co-precipitation method can be summarized as follows:the pH of the solution is 10,the calcination time is 20 h.The pH and the calcination time in the co-precipitation process have less influence on the phase structure of the as-prepared samples,However,the synthesis conditions have a significant influence on the photoluminescence performance of the as-obtained samples.The influence of synthesis conditions in the polyacrylamide gel process is the same as in the co-precipitation process.The Eu³⁺doped La₃PO₇ sample obtained at pH 10,and calcination time 10 h displays the strongest emission intensities than other samples for the polyacrylamide gel method.The La₃PO₇:Eu³⁺samples obtained with different techniques display similar emission features.Furthermore,the samples prepared by co-precipitation method exhibit stronger emission intensities compared with the samples via polyacrylamide gel process.