Dy3+ and Dy3+/Ce3+ doped Al2O3 coatings obtained by plasma electrolytic oxidation: Photoluminescence and energy transfer from Ce3+ to Dy3+

Abstract

In this paper, Dy3+ and Dy3+/Ce3+ doped Al2O3 coatings were synthesized by plasma electrolytic oxidation process of aluminum. Structural and photoluminescence (PL) properties of obtained coatings as well as energy transfer mechanism from Ce3+ to Dy3+ were studied. The PL excitation and emission spectra of Al2O3:Dy3+ featured weak bands attributed to f-f transitions of Dy3+. The PL emission spectrum of Al2O3:Dy3+ exhibits three emission bands in blue-yellow-red regions, assigned to 4F9/2→6H15/2, 4F9/2→6H13/2, and 4F9/2→6H11/2 transitions of Dy3+, respectively. Under middle UV excitation the Ce3+ in Al2O3 emits broad band, peaked at about 330 nm, attributed to the 5d→4f transition of Ce3+. Because of the strong overlap between the PL emission of Ce3+ and the PL excitation of Dy3+ in Al2O3, energy transfer from Ce3+ to the Dy3+ in Al2O3:Dy3+/Ce3+ is observed upon 285 nm excitation. PL emissions due to 4F9/2→6HJ (J = 11/2, 13/2, and 15/2) transitions of Dy3+ in Al2O3:Dy3+/Ce3+ is two to three orders of magnitude larger than in Al2O3:Dy3+. The values of CIE chromaticity coordinates for Al2O3:Dy3+/Ce3+ suggest their application for cold white light emission.