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.