Synthesis And Properties Of Rare Earth Doped RE₂P₄O₁₃（RE=Y,Gd） Luminescent Materials

The rare earth-doped superphosphate luminescent materials were prepared by co-precipitation method.The phase structures,morphologies,thermal properties and optical properties of the prepared samples were analyzed by X-ray powder diffraction（XRD）,scanning electron microscopy（SEM）,Fourier transform infrared spectroscopy（FT-IR）,and thermogravimetric and differential scanning calorimetry（TG-DSC）The co-precipitation method was used to prepare Eu³⁺doped Y₂P₄O₁₃ luminescent materials.The effect of the synthesized conditions,such as the n（Y+Eu）/n（P）ratio,different pH adjusters,calcination temperature,calcination time,Eu³⁺doping concentration,on the phase structures and luminescent properties of the crystals were investigated The results show that the preparation conditions directly affect the phase structures of the samples.When n（Y+Eu）/n（P）is 1:2.1,the pH solution is adjusted with ammonia bicarbonate,the calcination time is 15 h,the calcination temperature is 1000℃,and Eu³⁺doping concentration is 10 at%,the samples are Y₂P₄O₁₃ crystals with orthogonal structure.In addition,a small amount of Y（PO3）3 crystals were also observed.From the emission spectra of the Y₂P₄O₁₃:Eu³⁺samples,some emission peaks of Eu3＋can be seen at 593 nm（5D0→7F1）,620 nm（5D0→7F2）,and 696 nm（5D0→7F4）,and the strongest emission peaks belong to the 5D0→7F1 transition.the Y₂P₄O₁₃:Eu³⁺samples emit strong orange-red light.When the doping concentration of Eu³⁺is greater than 10 at%,a concentration quenching phenomenon is observed.The concentration quenching mechanism is quadrupole-quadrupole interaction.The co-precipitation method was used to prepare Eu³⁺doped Gd₂P₄O₁₃ luminescent materials.The phase structures and luminescent properties of the crystals were used to investigated.The effects of some preparation conditions on strucutres and optical properties were also discussed.The results show that the preparation conditions directly affect the phase structures of samples.The pure pahse Eu³⁺doped Gd₂P₄O₁₃ crystals with orthogonal structure can be obtained when n（Gd+Eu）/n（P）is 1:2.2,ammonia solution is used to adjust the pH solution to 2,the calcination time is 15 h,the calcination temperature is 1100℃,and Eu³⁺doping content is 5 at%.The excitation spectra of Gd₂P₄O₁₃:Eu³⁺samples show that the O2-→Eu³⁺charge transition band at 254 nm and the 8S7/2→6I9/2,6P3/2,6P5/2,6P7/2 transition excitation peaks of Gd³⁺ions around 274 nm,299 nm,307 nm,and 312 nm,respectively.The remaining sharp excitation peaks belong to the transition excitation peaks of the 7F0 to the 5D4,5L7,5L6,and 5D2 transitions of Eu³⁺ions.The strongest excitation peak at 274 nm of the samples belongs to the transition of Gd³⁺ion.The characteristic emission peaks due to Eu³⁺ions were obtained under the excitation of 274 nm,meaning that the energy transfer from Gd³⁺to Eu³⁺existed in Gd₂P₄O₁₃:Eu³⁺A series of Dy³⁺,Tb³⁺,Ce³⁺,Eu³⁺doped Gd₂P₄O₁₃ luminescent materials with different doping concentrations were prepared by co-precipitation method.And the phase structures and optical properties were analyzed.The results show that a small amount of rare-earth doping ions have less affects on the phase structures of samples.The emission spectra of Gd₂P₄O₁₃:Dy³⁺samples display strong blue emission peak at 479 nm,strong yellow emission peak at 573 nm,and weak red emission peak at 664 nm,attributing to the 4F9/2→ 6H15/2,6H13/2,6H11/2 transitions of Dy³⁺ ions,respectively.The optimal Dy³⁺ doping concentration is 1 at%.The Gd₂P₄O₁₃:0.5 at%Dy³⁺crystal emits white light.Under the excitation of 274 nm,the Gd₂P₄O₁₃:Tb³⁺samples emit the characteristic green emission peak of Tb³⁺at 543 nm（5D4→7Fs）.The optimal Tb³⁺doping concentration is 11 at%.The Gd₂P₄O₁₃:Ce³⁺crystals exhibit a broad blue emission peak due to the 2D3/2→4F5/2 transition of Ce³⁺under the excitation of 303 nm.A red-shift phenomenon of emission peak was found for Gd₂P₄O₁₃:Ce³⁺samples with the increase of Ce³⁺doping concentration.A energy transfer from Ce³⁺to Tb³⁺was found in the Ce³⁺and Tb³⁺co-doped Gd₂P₄O₁₃ samples,while the energy transfer from Ce³⁺to Eu³⁺cannot be proved in the Ce³⁺and Eu³⁺co-doped Gd₂P₄O₁₃ samples..The Tb³⁺and Eu³⁺co-doped Gd₂P₄O₁₃ samples emit white light due to the characteristic emission peaks of Tb³⁺and Eu³⁺ions.The intensities of emission peaks increase with increasing the doping concentration of Tb³⁺.The emission spectra of the Ce³⁺,Tb³⁺and Eu³⁺tri-doped Gd₂P₄O₁₃ samples display several emission pekas composed of characteristic emission peaks of Ce³⁺,Tb³⁺and Eu³⁺ions.The emergy transfer from Ce³⁺to Tb³⁺and from Tb³⁺to Eu³⁺in the Ce³⁺,Tb³⁺and Eu³⁺tri-doped Gd₂P₄O₁₃ samples was observedA series of Tb³⁺,Ce³⁺,Eu³⁺doped Y₂P₄O₁₃ luminescent materials with different doping concentrations were prepared by co-precipitation method.And the phase structures and optical properties were analyzed The results show that a small amount of rare-earth doping ions will not change the phase structure of Y₂P₄O₁₃ crystals.In the Y₂P₄O₁₃:x at%Ce³⁺（x=1-4）crystal,the emission spectrum Under the excitation of 324 nm,the Y₂P₄O₁₃:Ce³⁺samples show a broad blue emission peak of Ce³⁺Concentration quenching will be occurs when the Ce³⁺doping amount is above 3 at%.The Y₂P₄O₁₃:Tb³⁺crystals with excitation at 371 nm light exhibit the Tb³⁺emission peaks near 488 nm,544 nm,588 nm,and 622 nm.The strongest emission peak is the characteristic green light emission of Tb³⁺at 544 nm.Within the experimentally designed doping range,no concentration quenching was found.The emission spectra of Eu³⁺and Tb³⁺co-doped Y₂P₄O₁₃ crystals are dominated by the characteristic emission peaks of Tb³⁺and Eu³⁺ions.The emission peaks are all increase with Tb³⁺doping concentration increasing.The Eu³⁺and Tb³⁺co-doped Y₂P₄O₁₃ crystals emits white-light emission.ForThe characteristic emission peaks belonging to Ce³⁺,Tb³⁺,Eu³⁺were observed in the emission spectra of the Ce³⁺,Eu³⁺,Tb³⁺tri-doped Y₂P₄O₁₃ samples.And the samples emit green-light emission.