Elaboration And Luminescent Properties Of Rare-Earth Doped Glass Ceramics

Transparent glass ceramics (GCs), a new type of transparent hosts for rare earth (RE) ions doping, have attracted persistent attention recently due to their potential applications in lasers, scintillators, upconversion, quantum cutting and White Light Emitting Diodes (WLEDs) phosphors. GCs possess not only higher chemical and mechanical stability from glasses but also excellent characters from the precipitated crystals. It is thus highly desirable to combine advantages of glasses and crystalline materials via developing GCs. In this thesis, the preparation, structure and fluorescent properties of Eu doped GCs containing silicate, fluoride and phosphate nanocrystal were systematically investigated. Our results provide novel thought and direction for the development of new type thermostable and high quality light conversion material. The main contents are listed as follows:1. Eu-doped BaAl2Si2O8GCs:Eu3+and E2+co-doped aluminosilicate glasses and GCs containing BaAl2Si2O8were prepared by melt-quenching technique in air and their luminescent properties were investigated by excitation, emission spectra and lifetime measurements. Intensities of Eu3+and Eu2+emissions in GCs were enhanced by about9and20times compared to that in precursor glasses, respectively. More interesting, under380nm ultraviolet (UV) excitation, a perfect white light with chromaticity coordinates (X=0.333, Y=0.307) was achieved for GCs by combining intense red emission of Eu3+with broad blue-green emission of Eu2+. Our results indicate that mixed-valence Eu-doped BaAl2Si2O8GCs may provided a new platform for W-LEDs excited by UV-LED.2. Eu3+-doped transparent BaLuF5GCs:novel Eu3+-doped transparent oxyfluoride GCs containing BaLuF5nanocrystals were successfully fabricated by melt-quenching technique for the first time. Analyses of X-ray diffraction (XRD) patterns proved that the new precipitated GCs are crystallized in cubic BaLuF5based on isostructural BaGdFs theoretically. Transmission electron microscopy (TEM) measurement confirmed the presence of nanocrystals with mean size of10-22nm and homogeneous distribution among the glass matrix. Their luminescent properties were systemically investigated by excitation and emission spectra as well as luminescence decay curve measurements. Intense red emissions observed in GCs are attributed to the enrichment of Eu3+ions into BaLuFs nanocrystals. Such transparent and novel material may find potential applications in photonics. Besides, Lu-based transparent GCs may be promising materials for scintillators compared to crystals and transparent ceramics.3. Eu doped transparent LuPO4GCs:dual valence Eu doped precursor glasses were fabricated by melt-quenching technique in air atmosphere and transparent GCs containing tetragonal LuPO4nanocrystals were obtained firstly by further heat treatment. Their microstructure and luminescent properties were investigated by XRD, TEM, absorption spectra, excitation and emission spectra, as well as fluorescence decay curves. The prominent Stark splitting, low forced electric dipole5D0-7F2transition and long decay lifetime of Eu3+emission for glass-ceramics reveal the incorporation of Eu3+into LuPO4nanocrystals while Eu2+still reside in glass matrix. The enhancement of Eu2+emission with increasing crystallization temperature was observed in GCs, and the fluorine evaporation causes the reduction of Eu3+to Eu2+. Under380nm excitation, the emitting color of samples shifts from red to white with increasing annealing temperature. Our results indicate that LuPO4based GCs doped with RE ions may find application in photonics and white-emitting phosphors for UV LED chips.