Ce^3+/Eu²⁺ Doped Al₂O₃ Coatings Formed by Plasma Electrolytic Oxidation of Aluminum: Photoluminescence Enhancement by Ce³⁺→Eu²⁺ Energy Transfer

Plasma electrolytic oxidation (PEO) of aluminum in electrolytes containing CeO₂ and Eu₂O₃ powders in various concentrations was used for creating Al₂O₃ coatings doped with Ce³⁺ and Eu²⁺ ions. Phase and chemical composition, surface morphology, photoluminescence (PL) properties and energy transfer from Ce³⁺ to Eu²⁺ were investigated. When excited by middle ultraviolet radiation, Al₂O₃:Ce³⁺/Eu²⁺ coatings exhibited intense and broad emission PL bands in the ultraviolet/visible spectral range, attributed to the characteristic electric dipole 4f⁰5d¹→4f¹ transition of Ce³⁺ (centered at about 345 nm) and 4f⁶5d¹→4f⁷ transition of Eu²⁺ (centered at about 405 and 500 nm). Due to the overlap between the PL emission of Al₂O₃:Ce³⁺ and the PL excitation of Al₂O₃:Eu²⁺, energy transfer from Ce³⁺ sensitizer to the Eu²⁺ activator occurs. The energy transfer is identified as an electric dipole–dipole interaction. The critical distance between Eu²⁺ and Ce³⁺ ions in Al₂O₃ was estimated to be 8.6 Å by the spectral overlap method. View Full-Text