Di Weihua, Wang Xiaojun, Chen Baojiu, Lu Shaozhe, Zhao Xiaoxia
Key Lab of Excited-State Processes, Changchun Institute of Optics, Fine Mechanics and Physics, Chinese Academy of Sciences, Changchun 130033, PR China.
J Phys Chem B. 2005 Jul 14;109(27):13154-8. doi: 10.1021/jp051894i.
In this work, we use the solution precipitation method to synthesize Tb3+-doped yttrium orthophosphate, which is a green-emission luminescent material. The evolution of hydrated yttrium orthophosphate (YPO4.2H2O) to dehydrated yttrium orthophosphate (YPO4) is observed in the heat-treatment process, simultaneously, accompanying the structural transformation from monoclinic churchite-type to tetragonal xenotime-type structure. Furthermore, the luminescent efficiency of Tb3+-doped YPO4 presents a sharp jump at a critical temperature in this heat-treatment process. Interestingly, this critical temperature is close to the structural transformation temperature. The remarkable change of luminescent efficiency seems to be related to the structural transformation. However, the FTIR and fluorescent decay measurements at 10 and 300 K indicate that the OH group is the origin of luminescent efficiency change. OH- ions with high vibration frequency provide an efficient means to quench the luminescence. The comparison of the luminescent efficiency, OH- content, and lifetime of 5D4 of Tb3+ between two samples with the same crystal structure proves that the structural transformation has no significant effect on the luminescent efficiency and lifetime. On the basis of these results, it is proposed that correctly preventing OH- ions inside the host matrix or effectively eliminating them may improve the luminescent efficiency greatly. This idea also may be applied to other optical systems.
在本工作中，我们采用溶液沉淀法合成了掺Tb3+的正磷酸钇，它是一种绿色发光的发光材料。在热处理过程中观察到水合正磷酸钇（YPO4·2H2O）向脱水正磷酸钇（YPO4）的转变，同时伴随着结构从单斜磷钇矿型向四方磷钇矿型结构的转变。此外，在该热处理过程中，掺Tb3+的YPO4的发光效率在一个临界温度处出现急剧跃升。有趣的是，这个临界温度接近结构转变温度。发光效率的显著变化似乎与结构转变有关。然而，在10 K和300 K下的傅里叶变换红外光谱（FTIR）和荧光衰减测量表明，OH基团是发光效率变化的根源。具有高振动频率的OH-离子提供了一种有效的发光猝灭方式。对具有相同晶体结构的两个样品之间Tb3+的5D4的发光效率、OH-含量和寿命进行比较，结果表明结构转变对发光效率和寿命没有显著影响。基于这些结果，提出正确阻止主体基质内部的OH-离子或有效消除它们可能会大大提高发光效率。这一想法也可能适用于其他光学系统。
