LaOBr1-xClx:Tb3+晶体中Tb3+的4f75d1激发态的能级分裂

在室温和78K下对六种LaOBr1-xClx:Tb3+(x=0、0.2、0.4、0.6、0.8、1.0)粉末样品的4f75d1激发谱进行了研究,在78K下观察到了Tb3+离子的4f75d1激发态的能级分裂。利用点电荷模型计算得到了LaOBr1-xClx:Tb3+晶体中Tb3+的4f75d1激发态能级的分裂值。考虑到LaOBr1-xClx:Tb3+化合物的共价性等因素,三个因子α=0.32,β=0.67-1.08,γ=0.32-0.40相应地引入到Akm展开式中与O.X.La有关的各项中。计算得到的能级分裂值和实验值相差小于20cm-1。

THE ENERGY LEVEL SPLITTING OF THE EXCITED Tb3+4f75d1 STATE IN LaOBr1-xClx CRYSTALS

LaOBr:Tb and LaOCl:Tb are efficient cathodo-and x-ray phosphors.They have the type of structure as PBFC1 and consist of alternative layers of La-O-La-X-La. Their tetragonal unit cell is shown in Fig.11]. Each La3+ ion is 9-coordinated by 4 oxide ions on one side and 5 halide, ions on the other side. Four halide ions locate at equal distance to La3+ and the fifth one locates further. The doped Tb3+ ions replace the La3+ ions in a point site of C4v symmetry. Holsa and coworkers have studied the splitting of the ground 7Fj stats of Tb3+ in LaOCl matrix2]. The authors have investigated the physico-chemical properties and luminescence of LaOBr1-xClx:Tb system in detail3]. The lattice constants a and c change linearly with the composition x. This shows that the system forms complete solid solution.