Luminescent Properties of Rare-Earth-Metal Ion-Doped KLaNb₂O₇ with Layered Perovskite Structures

Rare-earth-metal ions (Pr3+, Sm3+, Eu3+, Tb3+, Dy3+, and Er3+) doped in KLaNb2O7 with a layered perovskite structure showed photoluminescence by excitation of the two-dimensional host at 77 K. Dy3+- and Er3+-doped KLaNb2O7 showed the luminescence of both rare-earth-metal ions and host. In contrast, Pr3+-, Sm3+-, Eu3+-, Tb3+-doped KLaNb2O7 showed only the luminescence of their rare-earth-metal ions by host excitation, while the host luminescence was almost quenched. In the latter group, the characteristics of Tb3+- and Pr3+-doped KLaNb2O7 with respect to the temperature dependence of photoluminescence, afterglows and thermoluminescence were different from those of the others, suggesting that the hole-trapping process by the Tb3+ and Pr3+ played an important role for the characteristic behaviors. On the other hand, Sm3+-doped KLaNb2O7 showed bright photoluminescence and thermoluminescence as a unique characteristic of the KLaNb2O7 system. In this process, Sm3+ ions in the perovskite layers seem to work as electron-trapping sites.