Optical spectra of triply-charged rare-earth ions in polycrystalline corundum

Solid samples of polycrystalline corundum α-Al₂O₃ activated by triply-charged rare-earth ions RE³⁺ (R=Eu³⁺, Er³⁺, Pr³⁺) were synthesized by the sol-gel technology. Characteristic narrow-line optical absorption and luminescence spectra produced by intraconfigurational 4f-4f transitions in RE³⁺ ions have been measured. RE³⁺ ions have been established to form one dominant type of optical centers in the corundum matrix, and the energy diagram of Eu³⁺ and Er³⁺ Stark levels in corundum has been determined. Fiz. Tverd. Tela (St. Petersburg) 40, 1442–1449 (August 1998)