Luminescent Properties Of Trivalent Rare Earth Ion Activated Novel Phosphors

In this paper, some novel fluorescent materials were synthesized by high temperate solid-state method with four kinds of trivalent rare earth ion Dy3+, Tb3+, Eu3+ and Sm3+ as the main activator, and KMg La(PO4) 2 as the main host along with Li Y(Mo O4)2. We studied their luminescent properties and a preliminary theoretical analysis is shown as follows:(1) A series of single white light-emitting phosphors of KMg La1-x(PO4)2:x Dy3+were synthesized via high temperature solid-state reaction. Photoluminescence excitation(PLE) and photoluminescence emission(PL) properties were systematically investigated.It indicates that under near ultraviolet excitation(n-UV), the emissions of Dy3+ ions are observed at 481 nm(blue) and 575 nm(yellow). The critical distance is calculated to be 1.136 nm, and the energy transfer type between Dy3+ ions is confirmed as the dipole-dipole(d-d) interaction according to the theory of Dexter. Optimal emission intensity of the samples is determined as x=0.05. KMg La0.95(PO4)2: 0.05Dy3+ has good white emission and its CIE chromaticity coordinates is close to that of standard white light.(2) A series of novel green-emitting phosphors of KMgLa1-x(PO4)2:x Tb3+were synthesized via high temperate solid-state reaction. The critical distance is calculated to be 1.135 nm,and the ET mechanism in KMg La(PO4)2:Tb3+is confirmed as multipolar interaction.KMg La(PO4)2:Tb3+ has good green emission and its CIE chromaticity coordinates are shifted from light green to green, and to green-yellow with increasing the Tb3+content.The sample even has good thermal stability after the comparison of emission under different temperatures. These results demonstrate that the sample with absorption efficiency in n-UV region can play an important role in w-LED.(3) KMg La(PO4)2:Eu3+were synthesized via conventional solid-state reaction. The excitation spectra of KMg La(PO4)2:Eu3+ phosphors is consist of broad charge transfer band and a series of sharp peaks. The center of the most strong emission peak is located at 595 nm, which is due to 5D0→7F1 transition of Eu3+. The luminescence intensity enhances with increasing the Eu3+doping concentration, but the luminescence intensity decreases when doping excess Eu3+ ions, and the greatest integrated emission intensity is at the concentration of 0.10Eu3+. Some more research has been done on decay curves of the sample, and it becomes smaller and smaller as increasing Eu3+ content.(4) A series of KMgLa(PO4)2:Sm3+and Li Y(MoO4)2:Sm3+were synthesized via conventional high temperate solid-state reaction. The synthesized conditions and luminescence properties of their respective advantages of the two kinds of fluorescent materials are analyzed. The energy transfer types of the two samples are confirmed as the dipole-dipole(d-d) interaction. Researches show that the color coordinates of Sm3+doped KMg La(PO4)2 are unstable, but the color coordinates of Sm3+doped Li Y(Mo O4)2are changed little,and are shown in the red zone. These two samples have their own advantages and disadvantages,and they have potential application value during the future development of LED.