Effect of Structure Regulation on Energy Transfer between Rare Earth Ions in Apatite Structure Luminescence Materials

Author:Ma Xiao Xue

Supervisor:liao li bing mei le fu

Database:Doctor

Degree Year:2019

Download:9

Pages:137

Size:10324K

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Luminescence materials are also called phosphors.Single-phase polychromatic phosphors have attracted much attention in recent years.The acquisition pathways usually include structure regulation and energy transfer.To study the effect of structure regulation on energy transfer,a few series of single-phase multicolor phosphors with apatite structure A2B3(MO4)3C:Tb3+,Eu3+(A=Ba2+,Ca2+,Sr2+;B=La3+,Y3+;M=Si4+,Ge4+;C=F-,Cl-)were synthesized by traditional high temperature solid-state method.The crystallographic,optical and energy transfer characteristics of these phosphors were studied in detail.The main achievements include:1.A2La3(SiO4)3F:xTb3+,yEu3+(A=Ba2+,Sr2+,Ca2+)phosphors were synthesized by the structure regulation of bivalent cation substitution.The structure,luminescent properties of phosphors and the influence of bivalent cation regulation on the energy transfer between Eu3+/Tb3+were studied.The results show that the lattice constants decrease as the the radii of divalent cations decrease.By adjusting the doping ratio of Eu3+/Tb3+,the luminescence color of the three phosphors can be adjusted from green to yellow,orange,and finally to red.The energy transfer mechanism is quadrupole-quadrupole effect,and the three phosphors have good thermal stability.The band structures of Ba2La3(SiO4)3F and Sr2La3(SiO4)3F:Tb3+,Eu3+are obtained by density functional theory calculation.The conduction bands of BLSOF and SLSOF are mainly composed of trivalent cationic La-5d orbitals.The energy transfer efficiency between Eu3+/Tb3+increases as the radii of bivalent cations increase.Because Ba2La3(SiO4)3F phosphor has high energy transfer efficiency,it is selected as the base of other structure regulation studies to explore the effect of structure regulation on Eu3+/Tb3+energy transfer.2.The effect of trivalent cation regulation on energy transfer between Eu3+/Tb3+was studied by substituting Y3+for La3+.The results show that when Y3+replaces La3+,the lattice constants decrease obviously.The excitation spectra peak of Ba2Y3(SiO4)3F phosphors is 370 nm,and the energy transfer mechanism is still quadrupole-quadrupole interaction.Ba2Y3(SiO4)3F series phosphors can be changed from green to yellow,orange and red.Ba2Y3(SiO4)3F:0.15Tb3+,0.24Eu3+have the highest emission intensity,and the luminous retention rate is 71.53%at 423 K.Compared with Ba2La3(SiO4)3F series,the overlap area of Tb3+emission peak and Eu3+excitation peak decreases.The energy transfer efficiency decreases and the reduction is greater than that of bivalent cation structure regulation.3.Complex anion structure was regulated by substituting(GeO4)4-for(SiO4)4-.The effect of complex anion regulation on energy transfer between Eu3+/Tb3+was studied.The results show that when(GeO4)4-substitutes(SiO4)4-,the lattice constants increase obviously.The excitation spectra peak of Ba2La3(GeO4)3F phosphors is 375 nm,and the energy transfer mechanism is still quadrupole-quadrupole.Ba2La3(GeO4)3F series phosphors can be changed from green to yellow,orange and red.Ba2La3(GeO4)3F:0.15Tb3+,0.24Eu3+have the highest emission intensity,and the luminous retention rate is 66.86%at 423 K.Compared with the Ba2La3(SiO4)3F series,the overlap area of Tb3+emission peak and Eu3+excitation peak decreases,and the energy transfer efficiency decreases.The reduction range is smaller than that of trivalent cation structure regulation and larger than that of bivalent cation structure regulation.4 The channel anion structure was regulated by Cl-substituting F-,and the effect of channel anion regulation on energy transfer between Eu3+/Tb3+was studied.The results show that when Cl-substitutes F-,the lattice constants increase.The excitation spectra peak of Ba2La3(SiO4)3Cl phosphors is 376 nm,and the energy transfer mechanism is still quadrupole-quadrupole.Ba2La3(SiO4)3Cl series phosphors can be changed from green to yellow,orange and red.Ba2La3(SiO4)3Cl:0.15Tb3+,0.22Eu3+have the highest emission intensity,and the luminous retention rate is 72.89%at 423 K.Compared with the Ba2La3(SiO4)3F series,the overlap area of Tb3+emission peak and Eu3+excitation peak decreases,and the energy transfer efficiency decreased,and the reduction range was smaller than that of trivalent cation structure regulation,bigger than that of bivalent cation structure regulation,and slightly smaller than that of complex anion structure regulation.