Design And Fluorescent Properties Of Rare Earth Doped Fluoride Glass Ceramics

Glass-ceramics are interesting materials for various photonic applications. If doped with fluorescent ions they might combine the advantages of a glassy material with those of crystals. Glass ceramics have a good forming ability and isotropy, as well as high chemical, photochemical, and mechanical stability, and they provide advantageous fluorescence properties, such as high fluorescence quantum efficiency, long fluorescence lifetime, and good up-conversion properties. In this thesis, the preparation, structure and white light fluorescence emission of Eu3+-Dy3+ doped LaF3 glass ceramics were systematically investigated. The preparation, structure and the temperature controlled fluorescence spectra of Eu3+ and Dy3+ doped transparent glass ceramics containing α-NaYF4 are studied. The up conversion property of Er3+ single-doped NaGd F4 glass ceramics was also systematically investigated.(1) Dy3+ single doped, Dy3+-Eu3+ co-doped transparent glass-ceramics(GC) containing hexagonal LaF3 nanocrystals were fabricated by melt-quenching method and subsequent heating. The luminescent properties of resulting GC were being investigated. Excited by 390 nm, the Dy3+-Eu3+ co-doped GC exhibits bright white emission with CIE coordinating of(0.345, 0.333). Judd–Ofelt intensity parameters, radiative probability, luminescence branching ratio, cross-sections and effective bandwidth were calculated. The Judd-Ofelt parameters Ω2, Ω4, and Ω6 indicate that GC has a high asymmetrical and covalent feature. The resulting GC may be used in the white light-emitting diode fields.(2) Eu3+ and Dy3+ doped glass ceramics containing α-NaYF4 were fabricated by melt-quenching method and subsequent heating. The nanocrystal size is about 22 nm through the TEM. At the excitation wavelength of 398 nm case, Eu3+ doped glass ceramics emit strong fluorescence. In the Eu3+ and Dy3+ ions doped glass ceramics, when we use 392 nm wavelength light to excite a microcrystalline glass, we found that the fluorescence emission of 427 nm, 480 nm, 579 nm, 612 nm, 650 nm, 700 nm six band lies within the range. In addition, we also studied the fluorescence spectra of the glass ceramic under the change of temperature(25-300 degrees), and draws the conclusion that the changes of temperature lead to a level of nonradiative relaxation probability enhancement, and electronic anti cloth local steady state. So the fluorescence is quenched and the spectral intensity decrease. These properties indicates that the NaYF4 glass ceramics have potential applications in laser amplifier and improve the efficiency of solar energy battery.(3) Er3+ doped glass ceramics containing NaGdF4 were fabricated by melt-quenching method and subsequent heating. The nanocrystal size is about 30 nm. The glass ceramic has a very high efficiency of up-conversion in green luminescence. Particularly, the up-conversion intensity of GCD increases by a factor of 333 for 4S3/2â†'4I15/2 transition and a factor of 225 for 4F9/2â†'4I15 / 2 transition under the excitation of 980 nm and by a factor of 40.4 for 4S3/2â†'4I15/2 transition, a factor of 41.2 for 4F9/2â†'4I15 / 2 transition and a factor of 11.6 for 4I11/2 â†'4I15/2 transition compared with PG,respectively. This shows that Er3+ doped NaGdF4 glass ceramics has great potential applications in the aspects of fluorescent material model.