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

Abstract

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.

Zeolite-containing photocatalysts immobilized on aluminum support by plasma electrolytic oxidation

“…Al2O3 is an attractive host for rare-earth ions since it has many interesting properties such as high transparency from ultraviolet to near infrared region, excellent mechanical strength, high thermal conductivity, good chemical and photochemical properties, high melting point, etc. Ce 3+ doped Al2O3 PEO coatings exhibit an intense PL emission in ultraviolet/visible spectral range with PL maximum positioned around 345 nm under 285 nm excitation due to the transitions of Ce 3+ ions from 5d excited state to the 4f ground state [40][41][42]. i.e.…”

Formation and Properties of Oxide Coatings with Immobilized Zeolites Obtained by Plasma Electrolytic Oxidation of Aluminum

“…The total PL intensity of these coatings is the sum of PL originating from Al 2 O 3 species and Ce 3+ ions. Obviously, the main contribution to PL emission spectra is from Ce 3+ ions, as they exhibit an intense emission band at around 320-330 nm due to the 4f 7 →4f 6 5d 1 transition [30], which is especially visible when compared to the emission of the pure Al 2 O 3 coating formed in supporting electrolytes without the addition of pure or Ce-exchanged zeolites. This contribution increases with prolonged PEO processing time, suggesting an increase of Ce concentrations in the obtained coatings.…”

Luminescence and Energy Transfer of Color-Tunable Y2Mg2Al2Si2O12:Eu2+,Ce3+ Phosphors

“…It is well known that the 5d → 4f transition energy of Ce 3+ is slightly higher than that of Eu 2+ based on the energy level of the rare-earth ions when Ce 3+ and Eu 2+ are in the same crystal environment . Therefore, there is usually energy transfer from Ce 3+ to Eu 2+ , whether in oxides, nitrides, fluorides, nitrogen oxides, phosphates, borates, silicates, or in most aluminate and aluminosilicate . In these host materials, when Ce 3+ and Eu 2+ are codoped, the Forster resonant energy transfer may perhaps occur, and a necessary condition for the realization of the energy transfer process is the existence of a sufficient spectral overlap between the emission of the donor and the absorption of the acceptor, and a suitable distance between the donor and the acceptor .…”