Y/Gd/Eu三元稀土层状化合物的离子交换行为与光学性能

Anion-Exchange Behaviors and Optical Properties of Ternary Y/Gd/Eu Layered Rare-Earth Hydroxides

摘要:

采用低温液相沉淀技术合成出硝酸盐类Y/Gd/Eu三元体系的稀土层状化合物，通过自组装获得了花瓣状超薄纳米片，并研究了该化合物的硫酸根离子交换行为和光学性能。研究表明当硫酸根与硝酸根的摩尔比R=0.25时，硫酸根离子可以完全置换层状化合物层间的硝酸根离子。离子交换后层状化合物的发光强度减弱，Gd3+离子掺杂使Eu3+离子的配位环境发生改变，从而导致磁偶极子跃迁5D0→7F1 的两个发射峰的相对强度发生变化。硫酸根离子交换改变了层状化合物的热分解路径，阻碍了煅烧过程中颗粒间的表面扩散，从而获得了高分散的氧化物荧光粉（平均粒度~120 nm），该粉体呈现出Eu3+离子的5D0→7FJ的特征红光。Gd3+离子掺杂有效敏化了氧化物固溶体中Eu3+离子的发光，煅烧温度的提高也进一步增加了粉体的发光强度与量子效率，同时降低了荧光寿命。

Abstract:

Self-assembly layered rare-earth hydroxide (LRH) nanosheets of ternary Y/Gd/Eu system were synthesized at freezing temperature by a chemical precipitation route. The anion-exchange behaviors and optical properties of the LRHs were studied. At the SO42-/Ln3+ molar ratio (R) of 0.25, the SO42- almost repalces the NO3- located in the interlayer of the LRH via anion exchange, however, the photoluminescence (PL) intensity decreases. Gd3+ substitution for Y3+ has significantly changed the coordination environment of Eu3+, leading to different intensities for the splitting bands of 5D0→7FJ transition peaking at ~590 and 595 nm. Sulfate exchange inhibits surface diffusion and inter-particle sintering during calcination and well-dispersed oxide powders that exhibit typical Eu3+ red emission were hence obtained. Gd3+ addition sensitizes Eu3+ emission to enhance the PL intensity of the phosphors. Improved PL intensity and external quantum efficiency and decreasing fluorescence lifetime were observed at a higher calcination temperature.