Preparation And Luminescence Mechanism Of Blueish Green Long Afterglow Materials ZrP₂O₇

Long afterglow luminescent phosphors as green and environmental friend materials with storage of light and energy saving have found wide application in the signs and daily crafts.They should have excellent luminescent properties,chemistry stability,green environmental friend,and low cost.The long afterglow luminescent materials based on phosphates have the advantages of environmental friend,chemistry stability and easy fabrication.It is firstly reported in this work that a new kind of blue green long afterglow luminescent material ZrP₂O₇: Mn²⁺ has been prepared.The long lasting phosphorescent bluish green phosphors of ZrP₂O₇ as parent materials with Mn²⁺ions as luminescence centers,have been prepared with high temperature solid-state preparation.the luminescence properties of materials can be improved by doping low valence metal ions and rare-earth sensitized ions.The determination of the XRD and the analysis of phases show that ZrP₂O₇: Mn²⁺,M with doping various ions belong to the PDF No.49-1079?according to JCPDS standard card?.The dopant of ions causes a slight shrinkage of cells with the improvement of the performance of materials' structure,though it does not cause the change of.the phase structure.The excitation and emission spectra of the materials have been determinated,and their peaks are assigned to the transitions of energy levels,The nearby excitation peaks of 412 nm,400 nm,382 nm,369 nm and 332 nm are assigned to the transitions of the energy levels of 6A1?4T1?4G?,6A1?4T2?4G?,6A1?4E,4A1?4G?,6A1?4T2?4D?and 6A1?4E?4D?in Mn²⁺,respectively.The emission peak near493 nm is from Zr4+,ascribing to the blue light.The weak emission peak at 545 nm,the green,is ascribed to 4T1?6A1 transition of Mn²⁺.The blue and green light is consistent with the viewing colour.The persistent time of phosphor can be observed for more than 3 hours with naked eyes.The thermosluminescence spectra have been determined for the materials to obtain the energy traps depth with the suitable value of0.2-0.5 eV.The replacement of low valence ions(Na+,K+,Sr²⁺)for Zr4+ will be responsible for the oxygen vacancy defects in the material and the increase of its concentration.The increase of the oxygen concentration is beneficial to the luminescent properties of the material.In addition,the introduction of the doped ions are also beneficial to the fabrication of appropriate level trap,and the improvement of the luminescent properties of the materials.The luminescent properties of materials can be improved by the introduction of rare earth ions?Dy3+,Pr3+,Sm3+?as the sensitizing ions which can absorb the energy and then transfer it to the luminescent center due to the overlap of their energy levels.When the materials are exposed to light,the electrons will jump from the ground state to the excited state with the generation of electron/hole pairs in the material.Electrons in the excited state will relax to a relative low energy level,most of them will return directly to the ground levels with the emission of light,and the rest will be captured by the traps and then will be released back to the ground state to realize the afterglowing via the thermal disturbance.The afterglow properties of materials are dependent on the lifespan of electron/hole pairs.