Study On The Synthesis And Structure-property Relationship Of Ce³⁺/Eu²⁺-doped SrLiAl₃N₄ Based Phosphors

White light-emitting-diodes have been widely used in lighting and display area,due to its advantages of energy-savings,environmental friendliness,color-tunable,etc.However,high-performance rare-earth luminescent materials are needed to further improve the performance of devices,especially narrow-band red phosphors,which can balance high color rendering index and optimal luminous efficacy.Based on this,the synthesis,structure-property relations and luminescent thermal-quenching behavior of narrow-band red-emitting SrLiAl3N4:Eu2+ phosphors are studied.A series of work focuses on anion/cation substitution,co-doping of rare-earth ions,luminescence prediction for prototype compounds of the UCr4C4 structure type,etc.The main contents are as follows:(1)SrLiAl3N4:Eu2+ phosphors are synthesized via high-temperature solid-state reaction.The starting nitride materials are prepared by metal nitridatioa To study on the crystallization characteristics and luminescence properties,the synthetic conditions are optimized by adjusting sintering temperatures,reaction times,fux type and addition amount.(2)Two phosphor series,Eu2+-doped Sr(LiAl)1-xMg2xAl2N4 and Sr(LiAl3)1-y(Mg3Si)yN4(x,y = 0-1),are successfully prepared using[Mg-Mg]substituting for[Li-Al]and[Mg3Si]for[LiAl3].The luminescence spectra can be tuning in the region of 614-658/607-663 nm.The varying luminescence behaviors with composition and structure are discussed based on centroid shift,crystal field splitting and Stokes shift.On the basis of experimental data,we construct the host referred binding energy(HRBE)and vacuum referred binding energy(VRBE)schemes of divalent/trivalent lanthanide-doped end-member compounds,and further give thermal quenching mechanism of these series phosphors.(3)The green light-excitable SrLiAl3N4:Ce3+ yellow phosphors are prepared.Its crystal structure and luminescence properties are analyzed.Based on Dorenbos's model and HRBE schemes,the excitation peaks are assigned for SrLiAl3N4:Ce3+.Compared with the data from the energy level schemes of Eu2+,the above analysis is reasonable in theory.On the basis of energy level schemes,it explains thermal quenching mechanism of SrLiAl3N4:Ce3+.(4)Based on the structural analysis and experimental data,oxygen can't substitute for nitrogen to regulate luminescent properties of SrLiAl;N4:Eu2+.The experiment shows that Ca can replace Sr to tune the luminescence spectra from 648 to 669 nm,while Ba cannot.There is no red long afterglow for Eu2+/RE3+co-doped SrLiAl3N4 phosphor(RE,rare earth ions).Based on the structural and spectral data analysis of UCr4C4 structure-type nitride,the luminescence spectra are predicted for Eu2+-doped KLiZn3O4,NaLi3SiO4,NaLi3GeO4,KLi3GeO4 and KLi3SiO4 compounds.