Photoluminescence properties of CuLa1−xLnxO2 (Ln: lanthanide)—intense and peculiar luminescence from Ln3+ at the site with inversion symmetry

Photoluminescence (PL) properties of CuLa0.98Ln0.02O2 (Ln: lanthanides with incomplete 4f electron shell) with delafossite-type crystal structure have been investigated. It has been elucidated that Ln3+ can be substituted for La3+ site in CuLa0.98Ln0.02O2 with inversion symmetry. PL spectra of CuLa0.98Ln0.02O2 showed intense PL lines due to magnetic dipole transition and weak ones due to electric dipole transition, showing agreement with the selection rule, according to which electric dipole transition should be forbidden by the inversion symmetry around Ln3+ in LaO6 octahedron. It was revealed that the observed PL mainly originated from charge transfer absorption between Ln3+ and O2−, resulting in higher intensity than those of Y2O3:Ln3+. Luminescence of materials with the same delafossite-type crystal structure could be controlled only by the kinds of Ln3+.