Study On The Luminescence Properties Of Borate And Phosphate Doped With Middle Rare Earth Ions

In this thesis,a series of middle rare earth ions(Sm³⁺、Eu³⁺、Tb³⁺、Dy³⁺)doped Ba₆RE₉B₇₉O₁₃₈（RE=Y,Gd）and Ca₈Mg Gd（PO₄）₇ phosphors were synthesized by high temperature solid state reaction and their photoluminescence properties were investigated.The specific experimental results include the following aspects:（1）For Ba₆Y₉B₇₉O₁₃₈,the photoluminescence properties of single-doped Ce³⁺ions were investigated,and the doping concentration of their best luminous intensity were determined.Among them,a series of Ba₆(Y_0.8-xCe_0.2Tb_x)₉B₇₉O₁₃₈（0≤x≤0.8）were synthesized and their photoluminescence properties were investigated.Meanwhile,the mechanism of energy transfer between Ce³⁺to Tb³⁺was demonstrated in detail and the energy transfer efficiency from Ce³⁺→Tb³⁺was also calculated which can exceed 90%.All the results imply that the efficient green phosphors under UV excitation can be designed by energy transfer.（2）For Ba₆Gd₉B₇₉O₁₃₈,a series of single-doped Ba₆(Gd_1-xRE_x)₉B₇₉O₁₃₈（RE=Ce,Sm,Eu,Tb,Dy）and co-doped Ba₆(Gd_0.8-xCe_0.2RE_x)₉B₇₉O₁₃₈（RE=Tb,Dy）phosphors were synthesized by high temperature solid state reaction.First,Le Bail refinements were performed to obtain the cell parameters.Second,the photoluminescence properties of Ba₆(Gd_0.8-xCe_0.2RE_x)₉B₇₉O₁₃₈（RE=Tb,Dy）were investigated in detail.The mechanism of energy transfer between Ce³⁺to Tb³⁺and Dy³⁺were demonstrated.The results indicate that energy transfer from Ce³⁺to Tb³⁺and Dy³⁺are confirmed via quadrupole-quadrupole interaction and dipole–dipole,respectively.The the energy transfer efficiency from Ce³⁺to Tb³⁺and Dy³⁺were also calculated which can exceed 90%and 65%,respectively.The results indicate that the luminous intensity of Tb³⁺especially Dy³⁺was improved through energy transfer.（3）Complete solid solutions of Ca₈Mg Gd_1-xTb_x（PO₄）₇（0≤x≤1）were prepared by high temperature solid state reaction.For the first time,the detailed structures for Ca₈Mg Gd（PO₄）₇and Ca₈Mg Tb（PO₄）₇ were determined according to Rietveld refinements on high quality PXRD.In both cases,Ca²⁺and Gd³⁺(or Tb³⁺)co-occupy M1,M2 and M3 sites and all in an eight-fold coordination by oxygen atoms.M4 is vacant.Mg²⁺resides at the relatively small M5 position with a typical octahedral coordination.By monitoring the Tb³⁺emission,strong absorptions due to the Tb³⁺f-d and f-f transitions can be observed as well as the typical Gd³⁺absorption,indicating the Gd³⁺to Tb³⁺energy transfer.Under excitation at 222 nm,typical ⁵D₄→⁷F_J（J=6-3）and⁵D3→⁷FJ（J=6-2）emissions were observed,and their different variations against the Tb³⁺content led to the tunable emission from blue to green.