Rare-earth doped glass-ceramics were prepared by heat-treating the precursor germanate glasses. The crystalline phases of the glass-ceramics were assigned to be NaAlGeO4 (NAG) and Mg2GeO4 (MG), and the primary particle sizes were derived to be ~31 and ~32nm, respectively. The secondary particle size of crystal grains was estimated to be ~30µm, and the large grain size is owing to the particles aggregation. Under 254 and 365nm radiation, Sm3+-doped glass-ceramics exhibit orange and reddish-orange fluorescences, and Eu-doped glass-ceramics present red and purplish-red lights, respectively. The investigation results of excitation spectra indicate that the Sm3+- and Eu-doped NAG-MG glass-ceramics can be excited efficiently by commercial UV and blue laser diodes, as well as blue and bluish-green LEDs.
μNear-infrared (NIR) emissions have been observed in Sm3+doped low phonon energy heavy-metal-gallate glasses. The full-widths at half-maximum (FWHMs) of three fluorescence bands peaking at 960, 1038, and 1185 nm were derived to be 31, 36, and 42 nm, respectively, and the spontaneous transition probabilities were calculated to be 66, 16, and 6 s-1. Maximum stimulated emission cross-sections ( σem) for NIR transition emissions were obtained to be 4.22´10-22, 1.37´10-22, and 0.71´10-22cm2, respectively. Investigations on multi-channel NIR transition emissions of Sm3+, especially on the ~1.19 μm emission, which lies in the low-loss wavelength region of transmission window, are beneficial for potential applications in infrared optoelectronic devices.
Based on the analysis of glass formation region of Y2O3-Al2O3-SiO2 glass system, the glass composition 5Li2O-18Y2O3-29Al2O3-48SiO2 (LYAS) in mol% central in the glass formation region of Y-Al-Si glass system was chosen for present work. The Tm3+ and Yb3+ were introduced as activators in LYAS glass. The glass samples were prepared by the high-temperature solid-state melting and then the derived YAG glass-ceramic was obtained by heat-treating the precursor glass. The X-ray diffraction (XRD) and scanning electron microscopy (SEM) analysis results indicate that the lattice constant of the obtained glass-ceramic is consistent with the pure YAG phase. The primary crystallite size is calculated to be 46nm and the crystal grains grow with excellent orientation (444) in the internal network. The secondary particle size is estimated to be ~8μm and the large grain size is owing to the particles aggregation. The crystal grains distributed uniformly in the glass matrix, and consistent well with the XRD analysis results.
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