Studies of electron-vibrational interaction and crystal field splitting in 5d states of Eu²⁺ in CaAl₂O₄ co-doped with Eu²⁺ and Er³⁺

CaAl₂O₄ co-doped with Eu²⁺ and Er ³⁺ were prepared by the solid-state reaction method and investigated for their photoluminescence properties. Broad band UV excited luminescence was observed for CaAl₂O₄ : Eu²⁺, Er³⁺ in the blue region due to transitions from the 4f⁶5d¹ to the 4f⁷ configuration of the Eu²⁺ ion. From the analysis of excitation and emission spectra, the crystal field splitting of the 5d states of Eu²⁺and the parameters of electron-vibrational interaction, such as the Huang-Rhys factor, effective phonon energy and zero-phonon line position of this system, were estimated for the first time.