Design And Multifunctional Application Of The Luminescence Materials Based On The 4f-4f Transitions Of Rare Earth Ions

The 4f electronic configuration of rare earth ions has the rich structures of energy levels. The emission wavelengths of 4f-4f transitions cover the range from ultraviolet, visible to infrared light. The diversified transition properties determine wide application prospects in many areas. Among them, the Eu3+, Tb3+ doped luminescence materials have been used in the plasma panel displays (PDP), white light emitting diodes (LED), fluorescent lamp and field emission displays (FED) due to the strong red and green emission intensities. The Dy3+ doped luminescence materials can generate warm white light emission in a single phase, which shows the potential for applications in general lighting. The luminescence materials doped by Pr3+, Tm3+, Nd3+, Ho3+, Er3+ and Yb3+ present excellent up-conversion characters and can be applied to the areas of biological fluorescent labeling and drug delivery. The emission of Gd3+ locates at the ultraviolet region. Although it is not suitable as a luminescence center, Gd3+ in the host can help to transfer energy between the luminescence center and host. However, on the one hand, in application, the current commercial phosphors have been found many disadvantages in the respects of luminous efficiency, color rendering, decay time, cost, etc. On the other hand, in theory, luminescence mechanism is not yet entirely clear when the luminescence materials are excited by the electron beam and vacuum ultraviolet (VUV) light. Thus, developing more efficient luminescence materials and explaining the ambiguities fundamental processes in physics is a question which cannot be avoided. In our work, we have synthesized a series of rare earth ions doped silicate, borate, vanadate and fluoride by the thermo-decomposition reaction of nitrates, high-temperature solid-state method and hydrothermal method, investigated the luminescence properties and luminescence mechanism, and finally evaluated the promising applications in the different areas. The main contents of the thesis are as follows:1. In the first part,1) we have synthesized the samples Tb3+/Eu3+ doped GdAl3(BO3)4 by the nitrate pyrogenation method, investigated the photoluminescence properties under the excitation of UV/VUV light, and discussed the sensitization of Gd3+/Ce3+ to Tb3+/Eu3+.2) We have synthesized the samples Tb3+/Eu3+ doped KBaY(BO3)2 by the solid state method, deconstructed the structure and found that the active ion Tb3+ shows the high luminescent quenching concentration in the host KBaY(BO3)2. The optimal emission intensity of KBaY(BO3)2:Tb3+ approximates to that of commercial green phosphor and the decay time is shorter：3) we have synthesized the samples Tb3+/Dy3+ doped Ca4GdO(BO3)3 by the solid state method, investigated the photoluminescence properties of Dy3+ in a non-centrosymmetric site, and discussed the sensitization of Tb3+ to Dy3+.2. In the second part, we have synthesized the samples Na3GdSi3O9:xTb3+(0.001≤x≤0.5) by the solid state method and investigated the energy transfer mechanism of Gd3+-Tb3+. We have found that the emission color of the samples can change gradually from blue to white and eventually to yellow-green region excited by the VUV/UV light. At the same time, we also have found the quantum cutting luminescence performances in this host.3. In the third part, we have prepared the samples K2(Y, Gd, Lu)(WO4)(PO4) by the solid state method and firstly deconstructed its structure. Under the excitation of UV light, the WO4 2- group can efficiently absorb and transfer the energy to the active ions. The optimal emission intensity of sample K2Y(WO4)(PO4): Eu3+ is higher than that of Y2O3:Eu3+. Under the excitation of VUV light, the PO43-group can efficiently absorb and transfer the energy to the active ions. Under the excitation of electron beams, the samples K2Y(WO4)(PO4):Tb3+,Eu3+ show the high conductivity. The electron penetration depths at 2,4, and 6 kV are about 1.20,16.80 and 78.75 nm, respectively. In addition, we have found that Yb3+, Er3+, Tm3+, Ho3+ doped K2Y(WO4)(PO4) samples present the excellent up-conversion characters and Tb3+ doped sample K2Gd(WO4)(PO4) shows the quantum cutting properties, which indicate that the active ions with the 4f-4f transitions doped K2(Y, Gd, Lu)(WO4)(PO4) can be applied for PDP, LED and FED.4. In the fourth part,1) we have prepared the samples Sc(P, V)PO4:Dy3+ by the hydrothermal method. The morphologies of samples show the granular power with the size of about 600 nm. The photoluminescence analyses presents that the charge transition band of VO43- and the intensity ratio of yellow and blue emission peaks gradually change with the increase of P/V ratio, which results in the color-tunable emission. 2) We have prepared the samples Ca9Y(VO4)7:Eu3+, Dy3+, Sm3+, Pr3+ by the solid state method and investigated the photoluminescence properties under the excitation of UV light. By the sensitization of Bi3+ to Eu3+, the emission intensities of optimal sample Ca9Bi0.15 Eu0.8(V04)7 reach 159% and 199% of those of Y2O3: Eu3+ excited by the 395 and 465 nm, respectively, which implies that this phosphor has the potential application in the white LED.5. In the last part, we have synthesized a series of Tb3+, Eu3+, Yb3+, Er3+, Tm3+ and Ho3+ doped ScF3 samples by the hydrothermal method. The morphology, electronic structure, magnetism and tunable luminescence properties of the as-obtained samples are characterized. ScF3 has the indirect band gap of 6.075 eV, hinting at its potential good properties as the matrix. Most interestingly, it is found that under the UV, VUV and low-voltage electron-beam excitation, the as-obtained Tb3+, Eu3+ codoped ScF3 product exhibits multicolor emissions together with the probable energy transfer process, in competition with the energy absorption and broad luminescence of nanocrystal defects. Correspondingly, different luminescence mechanisms are proposed. Furthermore, Yb3+ -Tm3+, Yb3+-Er3+ and Yb3+-Ho3+ codoped ScF3 samples show good up-conversion luminescence properties. The real agreement is that ScF3 nanocrystals exhibit ferromagnetism at the room temperature. All of these beneficial properties could determine potential applications of these phosphors in photoluminescence areas, field emission display devices, bioseparation and magnetic resonance imaging.