沸石中Eu^(2+)的荧光光谱特性

Photoluminescence Properties of Divalent Europium Ion Doped in Zeolites

利用水热离子交换法在不同的沸石中引入稀土离子Eu3+,系统研究了在600～1000℃范围内氢气还原的掺铕沸石的荧光光谱,实验结果表明不同的还原温度和不同的掺杂浓度可改变Eu2+发射峰的位置和相对强度,说明了离子在沸石中所处的配位环境、形成的化学键的性质的不同。

Eu2+ plays an important role among the low valency rare-earth ions. Eu2+ behaves low stability because of its strong reduction capability. On the other hand, Eu3+ can be reduced to Eu2+ in the voids of zeolites at relatively low reduction temperature. It should be ascribed a lot to the specific structure of zeolites. In our work, Eu3+ was introduced into the voids of the zeolites by hydrothermal reaction and reduced to Eu2+ at the temperatures in range from 600degreesC to 1000degreesC. The effect factors in hydrothermal ion-exchange efficiency and structure stability of different zeolites are analyzed. The fluorescence spectra of Eu2+ doped zeolites manifest that Eu2+ incorporated in zeolites exhibits 4f(6) 5d(1) --> 4f(7) broad band transition which is sensitive to the effect of the surroundings. Some new phenomena demonstrate that changing the reduction temperature and the doped concentration can vary the positions and the relative strengths of the emission bands. For samples at the same doped concentration, the strength of emission band near 390nm weakens while emission near 480nm strengthens as the temperature is elevated. For samples reduced at the same temperature, the strength of emission band near 390nm strengthens while emission near 480nm weakens as the doped concentration increases. The emission at short wave will disappear and the long-wave band will be the single emission in the spectra of the samples prepared at relatively low concentration and high temperature. It is caused by the fact that Eu2+ ions occupy different locations inside the zeolites on different preparation conditions.