Preparation and 1.06μm Fluorescence Decay of Nd~(3+)-Doped Glass Ceramics Containing NaYF_4 Nanocrystallites

Considered to be a candidate for large-size bulk materials used in lasers and other fields,Nd~(3+)-doped glass ceramics containing NaYF_4 nanocrystallites are prepared.Using x-ray diffraction and transmission electron microscopy,we show that pure cubic NaYF4 is well precipitated in the glass matrix.To obtain the optical property of this material at 1.06 μm,the fluorescence decay of ~4F_(3/2) energy levels is measured and analyzed.It is found that the fluorescence lifetime decreases first and then increases with the increasing dopant concentration due to the existing but finally weakening energy dissipation.As a result,a long radiation lifetime of about 191-444μs is obtained at 1.06μm in the prepared material.It is thus revealed that Nd~(3+)-doped glass ceramic containing NaYF_4 nanocrystallites is a potential candidate as a near-infrared laser material.     

非稀土掺杂协同核壳包裹对氟化物纳米晶上转换发光性能的增强

为提高上转换纳米晶的发光效率,提出协同增强的策略,将核壳包裹和非稀土离子掺杂两种方式进行有效的结合,使上转换纳米晶的发光效率实现"1+12"的增强效果。以Na Gd F_4作为基质材料,Yb~(3+)和Er~(3+)分别作为敏化离子和发光离子,以Li~+离子和Na Gd F_4作为非稀土掺杂离子和包裹壳层来构建核/壳纳米结构,研究两种增强方式的协同作用对Na Gd F4∶Yb~(3+)/Er~(3+)纳米晶的上转换发光性能的影响。结果表明,Li+离子掺杂与包裹Na Gd F4壳层共同作用使得β-Na Gd F4∶Yb~(3+)/Er~(3+)纳米晶的上转换发光增强了39倍,明显优于单一方式的增强效果。通过一系列的优化实验结果发现,Li+离子的最佳掺杂摩尔分数为4%。基于以上实验结果,给出了非稀土离子掺杂核壳纳米晶协同增强上转换发光效率的机理。     

Numerical Modeling of Crystallization Nucleation in Glass with Temperature Dependent Viscosity

1 INTRODUCTION Knowing the nucleation rate at different tempe-ratures, especially the temperature when the nuclea-tion rate reaches its maximum for glass, is of bothscientific and technological importance. These dataare significant in understanding the stability of glassfor practical applications where the formation of nuc-lei and their subsequent growth to crystals must beavoided (such as for optical fibers, laser glass, opti-cal switching glass), as well as for preparing laserglass-ceram…