玻璃陶瓷又称为纳米微晶玻璃, 是玻璃基质中包含约10 nm的纳米微晶。在稀土掺杂的玻璃陶瓷中, 稀土主要掺杂在氟化物纳米晶中。这种材料在发光应用中具有氟化物和氧化物的优点, 是上转换发光和中红外发光效率高的基质材料。研究Ho3+/Yb3+共掺杂的玻璃陶瓷(50SiO2-50PbF2-1.0YbF3-0.5HoF3)的上转换和中红外发光性质。玻璃陶瓷吸收光谱的半高宽比玻璃前驱物更窄, 而且长波吸收峰的Stark劈裂更加明显, 表明稀土离子掺杂在晶体中。通过吸收光谱计算了J-O参数, Ω2值(0.17×10-20 cm2)比氟化物玻璃ZBLA(2.28×10-20 cm2)的低很多。在980 nm激光激发下, Ho3+/Yb3+共掺杂的玻璃陶瓷有很强的绿光上转换荧光和蓝光、 红光上转换荧光。与玻璃相比, 绿光和蓝光光强增强明显, 而红光基本不变。玻璃陶瓷中的Ho离子掺杂在声子能量低的PbF2晶体中, 低的声子能量使发光能级的无辐射弛豫率降低, 从而增加了绿光和蓝光的上转换效率。低的无辐射弛豫率同时也降低了红光上转换中间能级(5I7)的粒子数布居, 因此红光上转换没有增强。在980 nm激光激发下Ho3+/Yb3+共掺杂的玻璃陶瓷有很强的2.9 μm中红外荧光, 而在玻璃前驱物中观察不到中红外荧光。

In the present paper, the upconversion and mid-infrared fluorescence properties of Ho3+/Yb3+ co-doped 50SiO2-50PbF2 glass ceramic (GC) were studied. The GC has the following composition (in mol%): 50SiO2-50PbF2-1YbF3-0.5HoF3. The mixtures of about 10 g were placed in a corundum crucible and melted at 1 000 ℃ for 15 min in a SiC electric furnace in air and then poured on a brass plate. The GCs were obtained just by heat treatment at 450 ℃. The X-ray diffraction pattern of the GC indicates that very small size crystals were precipitated in the precursor glass by heat treatment. The GCs have as high transmittance as glasses. The GCs have higher absorption cross section and narrower absorption peaks compared to the corresponding glasses, indicating that fluoride is doped with Ho ions. The Judd-Ofelt intensity parameters were determined from the absorption spectrum and Judd-Ofelt theory. The Ω2 value is 0.17×10-20 cm2 lower than that of fluoride glass ZBLA (2.28×10-20 cm2), because of Ho3+ doping in PbF2 microcrystal. The intense green upconversion light was observed in Ho3+/Yb3+ co-doped 50SiO2-50PbF2 GCs excited by 980 nm laser diode. A main emission band centered around 540 nm (green), and three week emission bands centered around 420 nm(violet), 480 nm (blue), and 650 nm (red) which correspond to the Ho3+: (5F4→5I8), (5G6→5I8), (8K3→5I8) and (5F5→5I8) transitions, respectively, were simultaneously observed in GCs. Compared with the glass sample, GCs have significantly intension in the green and blue upconversion fluorescence, and not significant change in the red upconversion fluorescence. Those changes are because that Ho ion in GCs locates in lower phonon energy environment than in glasses. Lower phonon energy can make the nonradiative relaxation rate reduce, which improves the green light upconversion efficiency, at the same time reduces the population of the intermediate energy level (5I7) of the red light radiation. The 2.9 μm mid-infrared light was observed in GC sample, but not in glass precursor excited by 980 nm laser diode.