The Preparation And Luminescence Properties Of Phosphate Phosphors Via Energy Transfer And Altering Host Composition

In recent years,as the development of ultraviolet /near ultraviolet light emitting diode(UV/NUV-LED),an increasing number of researchers are devoting themselves to the study of rear-earth ions doped phosphors,which can efficiently excited by ultraviolet /near ultraviolet irradiation.Therefore,the combination of UV/NUV-LED and various phosphors can tremendously enrich emitting colors of LED devices.For this reason,three types of phosphors were designed and synthesized via a combustion-assisted synthesis technique.Their luminescence properties and energy transfer have been investigated in details.A new strategy has been suggestedfor the development of rare earth ions doped phosphors used in the field of UV/NUV-LED.Firstly,three color tunable phosphors Mg3(PO4)2:Eu2+,Mn2+,Mg21Na4Ca4(PO4)18:Eu2+,Tb3+,Mn2+ andSr8MgLa(PO4)7: Ce3+,Eu2+,Mn2+ were synthesized.The incorporation of Eu2+ andMn2+ ions in the Mg3(PO4)2 host had been studied.The emitting color can be tuned from blue to red via changing the Mn2+ concentration.In the Mg21Na4Ca4(PO4)18: Eu2+,Tb3+,Mn2+ system,white emission can be realized by tuning the concentrations ofEu2+,Tb3+ and Mn2+.The quantum efficiency(QE)of sample was about 60%.IntheSr8MgLa(PO4)7: Ce3+,Eu2+,Mn2+system,theenergytransferprocesses ofCe3+?Eu2+,Ce3+?Mn2+ andEu2+?Mn2+ had been studied.Meanwhile,a chain energy tansfer of Ce3+?Eu2+?Mn2+has been proved to occur in this system.Secondly,a series of Ba2Mg1-xCax(PO4)2:Eu2+ phosphors were designed by utilizing the relationship of chemical composition and luminescence center.The emitting color of Ba2Mg(PO4)2: Eu2+ can be tuned from yellow to blue by the substitution of Mg with Ca.The optimized Ba2Mg0.4Ca0.6(PO4)2: Eu2+sample emits white light under UV excitation.Thirdly,two Ca3-xSrx(PO4)2:Eu2+,Mn2+and Ca8-xSrxMgLu(PO4)7:Eu2+,Mn2+ phosphors were designed by the combination of two strategies:(1)modifying the composition of the hosts;(2)energy transfer.The emitting colors of the two phosphors can be tuned in a broad range.The emitting color of Eu2+ doped samples can be tuned from blue to yellow by replacingCa2+withSr2+ions.Moreover,codoping Mn2+ions in the phosphorscan broaden the emitting color range.The two series ofphosphors can cover whole white light emitting range.The ideal white light emitting phosphors can be obtainedbyprecisely controlling the content of Sr2+ and Mn2+ions.