Photoluminescence of Ce³⁺ and Ce³⁺/Tb³⁺ ions in Al<inf>2</inf>O<inf>3</inf> host formed by plasma electrolytic oxidation

Abstract

In this paper, Ce3+ doped Al2O3 coatings were prepared by plasma electrolytic oxidation (PEO) processing of aluminum in electrolyte which contained CeO2 particles. The morphology, chemical composition, crystal structure, and photoluminescent (PL) properties of obtained coatings were investigated. The excitation PL spectra of Al2O3:Ce3+coatings show broad band in the range from 250 nm to 340 nm, which can be attributed to the transitions from 4f ground state of Ce3+ ions to the field splitting levels of 5d state. The emission PL spectra, obtained under 285 nm excitation, feature broad 5d→4f emission band in the ultraviolet/visible spectral range with the maximum peak located at around 345 nm. PL intensity depends of the content of Ce3+ ions incorporated into PEO coatings, i.e. PEO time and concentration of CeO2 particles in electrolyte. In addition, Ce3+ sensitized PL of Tb3+ions in Al2O3:Ce3+/Tb3+ coatings formed by PEO was examined. The emission PL spectrum of Al2O3:Ce3+/Tb3+ coating exhibits two distinct regions: the first region is related to Ce3+ PL band and the second region features a series of characteristic peaks of Tb3+ ions corresponding to 5D3→7FJ (J = 4, 5, and 6) and 5D4→7FJ (J = 3, 4, 5, and 6) transitions. A strong green 5D4→7F5 emission of Tb3+ ions upon excitation of Ce3+ is initiated by efficient energy transfer from Ce3+ to Tb3+ ions.